FLOW

DOCUMENTATION

Thank you for using FLOW ❤️

If you haven't already, please consider writing a review. They really help me out!

How do I upgrade?

First, make sure you back up your project files.

Next, install the latest version.

If for some reason the latest updates breaks your project (e.g. errors in the console), then try deleting the root folder for this asset, and reinstalling it.

If it still doesn't work, then let me know what the errors are so I can fix it. You can then revert to your back up, and wait for a fix to be released.

What is FLOW?

Unlike traditional fluid simulations that use 3D particles, FLOW works using columns of fluid that extend out from the ground. This means large areas of your scene can be covered in fluid using very little data, which leads to incredible performance. However, this difference does mean there are some limitations:

Within each fluid simulation there is only one column per XZ location, and each column stores the ground height + fluid data (depth, color, etc). This means you cannot have fluid floating above the ground, or multiple layers. Another way to think of this is that the fluid simulation is a heightmap running on top of another heightmap (e.g. a terrain), so if the fluid scenario you have in mind couldn't be represented using a heightmap, then you wouldn't be able to directly simulate it using FLOW.

For example: You cannot have fluid flowing through pipes, because you can't represent a pipe using a heightmap. However, you could place a 3D pipe model in your scene that drains fluid from one side, and emits it from the other.

For example: You cannot have fluid fill up spherical containers, because you can't represent a sphere using a heightmap. However, you could fill up an inverted semi-circle. If you really need to fill up a sphere, then I recommend you place a disc inside your sphere and adjust its size based on the fluid height to match the sphere.

For example: You cannot have fluid spray out from a hose, because flying water cannot be represented using a depth value alone. However, FLOW does come with a simple particle system that allows you to emit particles that turn into fluid when they hit the ground or the fluid surface.

Most of these common limitations can be worked around. However, there are some hard limitations that will never be possible. For example, there is no possibility of using FLOW with a voxel terrain system. You can read more information about limitations HERE.

Getting Started

Step 1 - Create a Simulation

Before you can add fluid to your scene, you must tell FLOW where in your scene you want the fluids to appear.

METHOD 1 Create a new GameObject, and add the FlowSimulation component to it.

METHOD 2 Right click in your Hierarchy tab, and select: FLOW > Simulation

METHOD 3 From the menu bar, select: GameObject > FLOW > Simulation

You should now see the FlowSimulation component in your inspector tab.

Step 2 - Adjust the Simulation Boundary

Fluid can only appear within the boundary of a simulation. You can adjust this using the Size and Center settings.

You can also adjust the HeightMin/Max settings, which allow you specify the minimum and maximum ground height that your fluid can flow over. For example, if your scene has a terrain that has an altitude range of 0 meters to 500 meters, then you should set HeightMin to 0 or lower, and HeightMax to 500 or higher.

NOTE You can see a preview of the simulation boundary size in the Scene tab.

Step 3 - Adjust GameObject Layers

Every object in your scene matching the HeightLayers setting will be converted into a heightmap using vertical (top down) raycasts. This heightmap is what the fluid simulation will flow over, so it's important you configure your scene layers so that it can be generated accurately.

For most projects, these layers should only include ground or wall objects. For example, you probably don't want your player character or collectible items to be considered 'ground' by the fluid simulation. Therefore, make sure these are on a different layer, or you can adjust the HeightLayers setting to exclude them.

To visualize what the simulations sees as ground, you can read the documentation HERE.

Step 4 - Adjust the Simulation Detail

The fluid is simulated using a grid of fluid columns. The distance between each column is controlled by the Separation setting, and then divided by the Resolution setting. You can use these to control the amount of columns in the whole simulation.

NOTE The more columns your fluid uses, the slower it will be.

NOTE Changing the simulation detail will change the way the fluid physics behaves.

Step 5 - Render the Fluid Surface

METHOD 1 Create a new child GameObject of your simulation, and add the FlowSurface component to it.

METHOD 2 Right click your fluid simulation GameObject in your Hierarchy tab, and select: FLOW > Surface

METHOD 3 Select your fluid simulation GameObject, and from the menu bar, select: GameObject > FLOW > Surface

You should now see the FlowSurface component in your inspector tab.

NOTE This component will be pre-configured with the Surface material in the MeshRenderer component's Materials list. If you'd like to adjust the overall look of your fluid surface, then you can duplicate this material, adjust the settings, and replace its material.

Step 6 - Add Fluids!

The easiest way to add fluids to your fluid simulation is to add a modifier to your scene.

METHOD 1 Create a new GameObject, and add the FlowModifier component to it.

METHOD 2 Right click in your Hierarchy tab, and select: FLOW > Modifier

METHOD 3 From the menu bar, select: GameObject > FLOW > Modifier

You should now see the FlowModifier component in your inspector tab.

If you set the Mode setting to AddFluid, then you can drag and drop a fluid into the Fluid setting. You can find a selection of pre-made fluids in the FLOW/Examples/Fluids folder.

NOTE If you want to create your own fluids then you can duplicate and modify an existing one, or add the FlowFluid component to your GameObject and drop it into the FlowModifier component's Fluid setting.

Your fluid should now appear in your scene!

If not, make sure the modifier is inside the boundary of your fluid. You can adjust its Size, and position it using the Transform component settings. You can see the boundary of both in the Scene tab when selected.

Do Fluids Work With Terrains and Custom Meshes?

Yes, fluids will automatically flow over and be blocked by terrains and any objects or meshes in your scene as long as they have colliders (e.g. MeshCollider).

This works by raycasting into the scene when the simulation starts, and then storing this height data with each fluid column.

You can control which objects appear using GameObject layers, and the FlowSimulation component's HeightLayers setting. The HeightMin/Max settings can also be used to control where the height cutoff is.

If the objects in your scene need to move then you can read the documentation HERE on how to make them automatically update the height data.

NOTE If your objects move a lot or float then you should change their layer or exclude them from the FlowSimulation.HeightLayers setting.

How is the Simulation Size/Performance?

By default, the fluid simulation uses 1 fluid column per 1 meter, which looks really good for most desktop game scenarios. Based on these settings, an entry level desktop could simulate active fluids across a 1km² map without issue, with higher end desktops being able to go to 2km² or even 4km² (the limit depends on the GPU, which is usually 16km²).

For mobile devices it's recommended that you reduce the FlowSimulation component's Resolution setting (e.g. to 0.5 for half the fluid columns - double the performance). This will retain the same fluid simulation size, but make it less detailed and therefore make it run faster. Due to mobile devices having a smaller display size, this reduction in simulation detail usually isn't noticeable.

To improve the performance even more, all parts of the fluid simulation are implemented with GPU acceleration.

How Can I Read Fluid Data (e.g. Depth)?

Right click in the Hierarchy tab, and select: FLOW/Sample

You should now see the FlowSample component in your inspector tab.

You can place this object anywhere in your scene using the Transform component's position, and it will automatically update with the fluid data at that XZ point (Y/height is ignored).

Keep in mind this component works asynchronously, so the data won't be available immediately. This component's OnSampled event will get invoked after each sample.

Once sampled, from code you can access this component's properties like FluidDepth, FluidVelocity, etc.

Are Custom Shaders/Materials Supported?

The fluids simulated by FLOW are rendered on top of terrains and other objects, so it will automatically work with them.

One thing to keep in mind is that the fluid is made transparent using grab pass or opaque texture (depending on rendering pipeline), so it cannot render transparent objects through it.

For example, if your camera is above the surface looking through the fluid, all transparent objects that are underwater will be invisible/disappear.

One exception is the Wetness feature, which requires you to use a shader/material that is designed to render FLOW wetness. See the Wetness documentation for more information.

How Can I Add Custom Fluid Types?

METHOD 1 Create a new GameObject, and add the FlowFluid component to it.

METHOD 2 Duplicate and rename one of the example fluids in the FLOW/Examples/Fluids folder.

You should now see the FlowFluid component in your inspector tab.

Feel free to change the Color, Viscosity, and other settings to your liking.

You can then drag and drop this prefab/GameObject into the fluid setting of a component like FlowModifier or FlowEmitter.

How Can I Remove/Drain Fluid?

Right click in the Hierarchy tab, and select: FLOW/Modifier

You should now see the FlowModifier component in your inspector tab.

You can then change the Mode setting to RemoveFluid, and move it using the Transform component's position setting.

Feel free to change the Size, Shape, and other settings to your liking.

How Can I Make The Ground Look Wet?

If you'd like the fluid simulation to make the ground wet and gradually dry over time, then this feature is for you.

STEP 1 - Simulate Wetness

Select your FlowSimulation component, and enable the Wetness setting.

Step 2 - Add Wetness Component

Next, add the FlowWetness component to the object you want the wetness effect to apply to.

This component has the Renderers setting - each material in these renderers will be sent wetness data. This list will automatically be set when you add the component, so you may not need to worry about it.

STEP 3 - Enable Material Wetness

Finally, enable the Wetness setting in the material settings used for your object.

NOTE This setting is only available if your material's shader implements FLOW wetness.

Custom Shaders

All materials that come with FLOW use shaders that implement the wetness feature. However, most other shaders will not support this.

All shaders that come with FLOW are built using the Better Shaders asset (not required).

If you have this asset, then you can simply stack the FLOW/Shaders/Wetness shader on top of your shader, and it will automatically support wetness.

If you don't have this asset, then you can look inside the code of this FLOW/Shaders/Wetness.surfshader file, and implement the equivalent yourself.

If neither of these options are suitable for you, then you must modify your materials to use the materials that come with FLOW (e.g. FLOW/Solid shader).

How Can I Render Underwater?

Underwater rendering is handled separately from the surface, to render it:

Right click your fluid simulation GameObject in the Hierarchy tab, and select: FLOW / Underwater

You should now see the FlowUnderwater component in your inspector tab.

Done!

How Can I Make Objects Float?

Any Rigidbody can be made to react to the fluid simulation with buoyancy and drag.

STEP 1 - Add Float Component

Select your Rigidbody GameObject, and add the FlowFloat component to it.

STEP 2 - Add Sample Point

Next you must add a sample point to the float - this lets the float know which part of your object is buoyant.

To add one, simply right click your float Rigidbody GameObject in the Hierarchy tab, and select: FLOW / Sample

You should now see the FlowSample component in your inspector tab.

STEP 3 - Adjust the Sample Point

Feel free to adjust the Radius and position of the sample point from the Transform component settings. While this sample point shape doesn't have to match your object, it should be somewhat similar.

OPTIONAL STEP - Add More Sample Points

If your object can't be well represented by just one sample point then feel free to repeat steps 2 & 3 as many times as you like in different locations and with different sizes.

NOTE The more sample points you add, the lower the performance will be.

Angular Drag

If your object only has one sample point then you will want to increase the FlowFloat component's AngularDrag setting. This will slow the rotation of the object when it's in water.

This isn't necessary for objects with multiple points because the Drag setting will work independently on each sample point and give the same effect.

Torque

If you want your object to remain upright (e.g. a buoy), then you can increase this setting. You can also decrease it to negative to make it bi-directional.

A similar effect can be achieved using multiple sample points, but this torque setting makes it easier to set up and run faster.

How Can I Make Fluids React to Scene Changes?

By default, the fluid simulation bakes the scene height data at the start. This means it won't react to any scene modifications (e.g. moving a fluid blocking object).

To make it react to scene changes, you can add the FlowObject component to your GameObjects. This component has the Center and Radius settings, which you can adjust to encapsulate your object. You can see the gizmo preview in the Scene tab to see what this looks like.

Once configured, the fluid simulation will automatically update if this object moves, rotates, scales, or gets de/activated.

If you're performing modifications from code (e.g. terrain height changes), then you can manually call the FLOW.FlowSimulation.DirtyGroundAll method.

NOTE To call this method you may need to add the FLOW assembly to the assembly definition file used by your code.

How Can I Detect When Fluid Appears Somewhere?

For a Single Point

Right click in the Hierarchy tab, and select: FLOW/Sample + Trigger

You should now see a new GameObject with the FlowSample and FlowTrigger components in your inspector tab.

You can then change the trigger Criteria setting and adjust the Transform.position.

The OnMet event will then be invoked when the criteria is met.

For a Specific Area

Right click in the Hierarchy tab, and select: FLOW/Sample Area + Trigger Area

You should now see a new GameObject with the FlowSampleArea and FlowTriggerArea components in your inspector tab.

You can then change the trigger Criteria setting and adjust the Transform.position.

The OnMet event will then be invoked when the criteria is met.

Why Does the Fluid Ignore My Object?

The fluid simulation flows over terrain and objects using a heightmap that is auto generated, and this height data is stored in each fluid column. This means there may be a discrepancy between what the fluid simulation thinks the ground looks like, and what the ground actually looks like in 3D.

To see what the fluid simulation thinks the ground looks like, you can add the DebugGround material to your FlowSurface component's MeshRenderer/Materials list.

For smooth shapes like a terrain, these heights usually line up well enough. However, for blocky objects like walls there will often be a difference, or they may be entirely missing from the ground data.

For example, if your simulation has a resolution of 1 fluid column per meter, and your wall is 0.5 meters wide, then it's possible for the wall to be placed between all fluid columns, and therefore be 'invisible' to the fluid simulation.

To fix this, you can:

METHOD 1 Adjust the position of your object until it appears in the simulation.

METHOD 2 Adjust the size of the collider to be wider, or increase the size of the object overall.

METHOD 3 Increase the FlowSimulation component's HeightRadius setting, for example to 0.5.

NOTE If you perform these modifications in-game, then you need to add the FlowObject component to the GameObject you're moving. This component will update the simulation ground heights as you modify the object. See HERE for more information.

Surface Shader Settings

Sink - This allows you to control the world space distance the edges of the fluid surface sink below the surface. This setting can be used to make the fluid look like it's on top of the ground with surface tension.

WAVE

Normal (RGB) Foam (A) - This is the texture used to show the animated waves and foam. The wave normal map is packed into the RGB channels, and the foam texture is packed into the alpha channel.

Strength Min - This allows you to set the normal map strength when the fluid is calm.

Strength Max - This allows you to set the normal map strength when the fluid is turbulent.

Strength Scale - This allows you to control how quickly the normal map strength will increase with fluid movement. A high value means even small disturbances to the fluid surface will cause the normal map to appear.

Tiling - This allows you to control how many times the normal and foam textures are tiled across the fluid surface.

Animation Speed - This allows you to control how often the normal and foam textures cycle through their animation.

TRANSPARENCY

These settings allow you to make the fluid surface transparent.

NOTE These techniques use grab pass or the opaque texture. Standard transparency is not suitable for fluid surfaces that can have many overlapping sections.

NOTE If you're using URP, you must enable the Opaque Texture setting in your pipeline settings asset.

Mode = None - The fluid surface will be opaque.

Mode = Vertical - The fluid surface will be given the same transparency value as the underlying fluid.

This is the fastest transparency technique, but it's also the least accurate.

Mode = Depth - This mode works like Vertical, but the transparency will factor in the distance between the fluid surface and the camera depth texture behind it.

This technique provides much better results with good performance, but the depth value may not be accurate. For example, at the edge of a terrain where there is nothing behind it, or if your fluid spikes up high and the background is very distant with very little actual fluid there.

NOTE If you're using the built-in render pipeline then you must add the CwDepthTextureMode component to your camera(s), and set the Mode to Depth or DepthNormals.

NOTE If you're using URP, you must enable the Depth Texture setting in your pipeline settings asset.

Mode = March Fluid - This mode works like Vertical, but the transparency will factor in the optical depth through the fluid. With this technique, the optical depth will be calculated using ray marching of the fluid data. This means submerged objects that aren't part of the fluid's ground data will be ignored.

Mode = March Fluid And Depth - This mode works like March Fluid, but the ray marching will factor in the camera depth texture. This means submerged opaque objects will correctly appear.

NOTE If you're using the built-in render pipeline then you must add the CwDepthTextureMode component to your camera(s), and set the Mode to Depth or DepthNormals.

NOTE If you're using URP, you must enable the Depth Texture setting in your pipeline settings asset.

Range Max - This allows you to set the maximum distance through the fluid you can see when the fluid has 0 opacity.

Step - This allows you set the world space distance between each ray marched sample through the fluid volume to find the optical depth.

Max Steps - This allows you to limit the amount of steps performed in case you have performance issues.

Depth Scale - This allows you to set the rate at which the camera's depth texture fades out based on camera distance. This is necessary because depending on the camera distance and camera near clipping plane distance, the depth texture values lose too much precision to be used.

NOTE This is only used with Mode = Depth and Mode = March Fluid And Depth.

STOCHASTIC

Enabled - If you enable this then the normal and foam textures will be stochastically sampled, which makes the texture tiling harder to notice.

Noise (A) - This allows you to set the noise texture used to perform the stochastic sampling.

FOAM

Brightness - This allows you to control the brightness of the foam texture.

Mode - This allows you to control how the foam blends with the underlying fluid surface.

Alpha = Smoothly alpha blend.

Cutout = Either 1 or 0 opacity, useful for more cartoon styles.

FACETED

Enabled - If you enable this then the fluid surface will have a low poly look.

Flat Amount - This allows you to control the strength of the low poly look.

Can I Request New Demo Scenes?

Yes, feel free to contact me using any of the methods listed in the FLOW/GUIDE asset.

I'm sure there are many use cases I haven't considered, and would love to make demo scenes of them if possible!

Known Issues / Limitations

Transparency

The fluid surface is made transparent using grab pass or the opaque texture depending on rendering pipeline, and the level of transparency is calculated using the depth buffer. Transparent objects don't write to the depth buffer, and won't appear in the opaque texture, therefore you will not be able to see them through the fluid. For example, if your camera is above the fluid surface and your transparent object is underwater, you will not be able to see it.

This is a limitation with transparent objects in general, though there are various ways to work around this issue.

Method 1 - Avoid Using Transparent Objects

This is the easiest and best solution when possible.

Method 2 - Use Cutout Transparency

This is also an easy solution that is suitable variety of objects. Unity's Standard shader for example can be set to RenderingMode = Cutout.

FLOW comes with the FLOW/Solid shader which is implements this.

Method 3 - Use Dithered Transparency

This is better than cutout transparency, and can look similar to real transparency when combined with a screen space AA technique like FXAA. However, most shaders don't support this, so you will have to modify them.

FLOW comes with the FLOW/Dither shader which implements this.

Method 4 - Render Semi-Transparent Areas Separately

This is a technique where the opaque parts of your object are rendered using cutout transparency, and the semi-transparent parts of your object are rendered using normal transparency.

This technique is suitable for objects that are mostly opaque with only semi-transparent areas around the edges. These semi-transparent areas will fail to render properly when mixed with the fluid surface though, so I don't recommend it.

Data Precision

The fluid data is stored using a collection of textures, where each pixel represents one fluid column. By default, important data like the fluid depth is stored using 32 bit floats, and less important data like the fluid color is stored using 8 bit bytes.

These defaults work well for most projects. However, if memory usage is a concern then you may want to switch from 32 bit floats to 16 bit floats. Conversely, if your project requires higher precision fluid mixing then you may want to increase from 8 bit bytes to 16 or 32 bit floats.

To adjust the precision of this data, you can modify the FlowSimulation component's Advanced / Precision___ settings. You can view the tooltip of each setting to see which fluid data is stored in that specific texture.

Fluid Viscosity Mixing

In real life, when you pour a low viscosity fluid like water on top of a highly viscous fluid like honey, the water will freely flow on top of it.

This is not possible to simulate in FLOW, because only one set of fluid data (e.g. depth, viscosity) is stored in each fluid column.

For example, if a column contains honey and water flows into it, the water will slowly mix into the honey and cause the overall viscosity to decrease. This results in the water appearing to stop or slow down as it hits the honey, and it gradually 'melting' as it fully mixes.

Fluid Simulation Interaction

Each fluid simulation is unique and separate. If you place one simulation next to another, or one on top of another, fluid will not be able to flow between them.

This same limitation exists for particles. When a particle is spawned, it is assigned to one simulation. It is not possible to freely spawn a particle in space and have it automatically apply to the first simulation it hits.

A solution to remove these limitations may be implemented in the future, but it is a fairly difficult feature to implement so it isn't such a high priority.

Determinism

The fluid simulation is updated on the GPU using floats, and the way floating point calculations are implemented on the GPU differs between some devices. Therefore, even if you start the exact same fluid simulation with the exact same settings, you may get slightly different results on different devices. Over a long enough timespan, these differences may become significant. So for example, it might not be a good idea to make a puzzle game that uses FLOW fluids as a main gameplay element that requires a very precise configuration/solution to solve, because it may be impossible for some people to achieve what you see.

Simulation Behavior vs Resolution

The fluid simulation is split up into a uniform grid of fluid columns. Each tick, these columns are updated using neighbor data from the four cardinal directions. This means the maximum possible speed a fluid can move is one column per tick. This usually isn't something you need to think about, but it means that changing the fluid simulation resolution (i.e. the separation distance between each column) will change how the fluid behaves/looks. For example, if your game is designed for desktop and mobile devices then you may want to reduce the FlowSimulation component's Resolution setting on mobiles to keep good performance. However, this means the fluids will behave differently on mobile, and may appear to flow faster.

The only way to make the simulation behave similarly with differing resolutions is to slow down the flow rate as you decrease the resolution. However, FLOW currently doesn't implement a feature like this, but I plan to add it.

Fluid Ground Data

The fluid flows on top of a runtime generated heightmap (i.e. for every XZ point within the simulation, there is an associated Y height value for the ground). This means it is not possible to have the fluid fill up a shape like the inside of a sphere, because a sphere does not have only one Y height for each XZ point.

Similarly, the fluid itself is stored using a single fluid depth value for each fluid column, so it's not possible to have fluid on top of another fluid unless they're in separate simulations (then they can't interact).

As long as you imagine the ground data as being a heightmap, and the fluid also being a heightmap, all the same limitations will apply to how the fluid could appear on the surface.

Spherical Planet Support (e.g. Space Graphics Toolkit)

While it's technically possible to implement this, it would require me to rewrite every feature with spherical calculations. This means it would require double the work to implement and support, but since only a small percentage of customers would use this, it wouldn't be worth it.

Voxel Terrains

The fluid flows on top of a runtime generated heightmap, and it's impossible to represent a voxel terrain using a heightmap. Therefore, there is no possible way to combine FLOW with voxel terrains.

Caves/Overhangs/Terrain Holes

The fluid flows on top of a runtime generated heightmap, and it's impossible to represent a these features using a heightmap. Therefore, there is no possible way to combine FLOW with these features.

Moving Containers (e.g. a Bucket)

You can move the fluid simulation with your container, and using the FlowModifier component you could apply force to the fluid to make it 'slosh' around. However, you wouldn't be able to freely rotate the container, and you wouldn't be able to pour fluid out. If you need these kinds of features then you should use a particle based fluid simulation like Obi Fluid.

Third Party Water/Ocean Assets

FLOW uses a custom shader to render the fluid surface. If you replace this shader/material with one from another asset, then the fluid will disappear. While it might be technically possible to combine the two shaders, it would require a lot of work and take up too much time to maintain.

While developing FLOW I experimented with mesh generation, which might allow for better compatibility with other water/ocean systems. However, the performance of this technique was unacceptable so I abandoned the idea.

Another thing to keep in mind is that most water/ocean assets rely on baked data and/or a flat water surface. These constraints allow them to easily implement many rendering features that are not possible to use with a fully dynamic fluid simulation like FLOW.

What Examples Are Included?

This is a list of the in-game example scenes and a description of what it shows.

Basic Setup

This shows you how to make a basic fluid scene filled with water. This is done by making a new GameObject with the FlowSimultation component - this will simulate any fluids you add to the scene. Next, make a new child GameObject with the FlowSurface component - this will render the fluid surface. You can then add a new GameObject anywhere in your scene with the FlowModifier component - this allows you to add/remove/etc fluid to the scene. In this scene this component''s Mode is set to AddFluid, and Fluid is set to Water. You can find more fluid types in the FLOW/Examples/Fluids folder.

Buttons

This shows you how to make UI buttons that can de/activate GameObjects that act as different tools. This is used in all the demo scenes to more easily show multiple effects. To use it, each child of the Tools GameObject has the FlowToolButtonBuilder component, which can automatically build a UI button that activates it.

Simulation Resolution

This shows you how the level of detail of the fluid simulation can be adjusted. By default the FlowSimulation component''s Size and Separation settings are used to control the detail, but you can also use the Resolution setting to quickly adjust this without changing the size. A value of 1 means standard detail based on the simulation . A value of 2 means there will be twice as many fluid columns used in the simulation, and therefore half the performance, and so on. Keep in mind the fluid physics will change slightly based on your resolution setting.

Fluid Types

This shows you how different types of fluid can be added to the simulation, and they will automatically mix together. This is done by changing the FlowModifier component''s Fluid setting. You can find more example fluids in the FLOW/Examples/Fluids folder, which you can drag and drop into this setting. You can also duplicate these and modify their settings to create your own, or add the FlowFluid component to your scene with custom settings and drag and drop that.

Custom Fluid

This shows you how to add custom fluid types to the scene, without using prefabs. This is done by adding the FlowFluid component to your scene, and customizing its settings. You can then drag and drop this component or its GameObject into the Fluid setting of your FlowModifier component.

Random Fluid

This shows you how to randomize the settings of a fluid emitted from a modifier. This is done by adding the FlowRandomizeFluid component to your scene, and setting its Target fluid to the fluid component you want it to modify. This component automatically activates when enabled, so it will randomize the fluid each time the modifier tool is activated.

Continuous Flow

This shows you how to continuously emit fluid. This is done using the FlowModifier component, and changing its Apply setting to Continuously.

Drain Fluid

This shows you how to remove fluid from the simulation. This is done by changing the FlowModifier component''s Mode setting to RemoveFluid. This will remove all fluid at the position of the modifier, within the specified Size.

Debug Ground

This shows you how to visualize what the fluid simulation thinks the ground looks like. This is done by adding the DebugGround material to the FlowSurface component''s MeshRenderer.Materials setting. The ground is generated using vertical raycasts that are stored in a heightmap, so there will usually be a difference between the simulation ground and the actual ground. Visualizing this difference allows you to optimize the position of your objects for maximum fluid simulation visual quality.

Too Thin

This shows you how to visualize what the fluid simulation thinks the ground looks like. This is done by adding the DebugGround material to the FlowSurface component''s MeshRenderer.Materials setting. The ground is generated using vertical raycasts that are stored in a heightmap, so there will usually be a difference between the simulation ground and the actual ground. Notice how the second wall is missed by the ground height generation, because it''s too thin.

Radius

This shows you how to make it so thin objects automatically get included in the ground height data. This is done by increasing the FlowSimulation component''s GroundRadius setting. Alternatively, you can adjust the position of the thin object so it lies on the sample points. Keep in mind the fluid flow may not align very well to thin vertical objects. For best visual results you may want to try to use thicker objects that are more tapered.

Trigger

This shows you how to detect when a certain amount of fluid has appeared at the specified location. This is done by making a new GameObject with the FlowTrigger component. You can then make a child GameObject with the FlowSample component. If the FlowTrigger component''s Criteria setting is set to FluidHeightAbovePosition, then the trigger will activate once the fluid rises above the sample''s Transform.postion.y. The OnMet and OnUnmet events can then be used to perform any custom action. In this example, they''re used to turn the object''s color from white to red.

Shared Sample

This shows you how multiple FlowTrigger components can use the FlowSample component. This can be used to perform different actions based on different fluid heights at the same location, and it gives better performance than using one sample per trigger, since each sample will return the same data.

Remove Blocker

This shows you how to remove a wall when the water level rises above a certain level. This is done by adding the FlowObject component to the wall, so it updates the ground height data when removed. A FlowTrigger is then placed in front of the top of the wall near its peak height, and its OnMet event is set to deactivate the wall GameObject.

Fluid

This shows you how to detect what kind of fluid is being sampled, based on a list of possible fluids you specify. This is done by adding the FlowSampleFluid component alongside the FlowSample component. You can drag and drop fluid components/prefabs into the Fluids list, and adjust the ___Threshold and ___Weight settings based on your requirements. The Triggers list can be used to perform a custom action when a specific fluid was detected.

Wetness

This shows you how fluid can make the ground wet, and gradually dry over time. This is done by enabling the FlowSimulation component''s Wetness setting, and adding the FlowWetness component to any GameObject you want the effect to apply to. Keep in mind these objects must use a material/shader that implements the FLOW wetness. The example shaders that come with FLOW have this feature if you enable the WETNESS setting. See the documentation for more information on how to implement this in your own shaders.

Underwater

This shows you how to render fluid even when the camera is underwater. This is done by making a new GameObject that is a child of the simulation. You can then add the FlowUnderwater component to it, and set its MeshRenderer.Materials list to use an underwater material. FLOW comes with the example Underwater material, which can be used.

Particle Emitter

This shows you how to emit particles that turn into fluid on impact. This is done by enabling the FlowSimulation component''s Particles setting, and making a new child GameObject with the FlowParticles component. You can then make a new GameObjects with the FlowEmitter component, and pick the Fluid you want it to emit.

Toggle Blocker

This shows you how to add and remove objects from the fluid simulation. This is done by adding the FlowObject component to them, and adjusting the Radius setting to encapsulate the whole object (see the Scene tab to verify). This component will automatically update the ground heights of the fluid simulation whenever the object changes.

Buoyancy

This shows you how to make physics objects float when they go underwater. This is done by adding the FlowFloat component alongside your Rigidbody component. You can then make a child GameObject with the FlowSample component to define where the float point is. You can adjust the Radius setting and the Transform.position to best fit your object. The FlowFloat component''s Buoyancy setting allows you to control how quickly the object floats to the surface.

Drag

This shows you how the FlowFloat component''s Drag setting can be used to slow an object down when it''s inside a fluid. This also means an object will accelerate if the fluid it''s inside is moving. This can be used in conjunction with the buoyancy to make the object move move smoothly.

Angular Drag

This shows you how the FlowFloat component''s AngularDrag setting can be used to slow an object''s rotation down when it''s inside a fluid. This can be used in conjunction with the buoyancy to make the object move move smoothly.

Torque

This shows you how the FlowFloat component''s Torque setting can be used to rotate an object upright while it''s in the water. This is useful for boats, buoys, and other simple objects you want to keep upright. Keep in mind you may need to use the AngularDrag setting to control the rotation.

Long Shapes

This shows you how to make long objects like capsules float. This is done by adding two FlowSample child GameObjects to the FlowFloat. One sample is used at the tip of the object, and one at the base.

Flat Shapes

This shows you how to make flat objects float. This is done by adding four FlowSample child GameObjects to the FlowFloat. Each sample is used at the corner of the object, allowing it to automatically float and rotate correctly to the fluid underneath.

Shape

This shows you how to add fluids in a custom shape. This is done using the FlowModifier component''s Shape setting. In this scene the shape is the FLOW asset logo, whose shape is stored in the alpha channel, so the shape''s channel setting is set to Alpha.

Dampen

This shows you how to stop or slow down fluid movement in a specific area. This is done using the FlowModifier component, with the Mode setting set to DampenForce. A Strength setting of 1 means the fluid will be completely stopped/frozen.

Add Fluid Below

This shows you how to add fluid below a certain point. This is done using the FlowModifier component with the Mode setting set to AddFluidBelow. This can be useful for initializing a scene with fluid that remains in a stable state, such as when applied to an island.

Paint Fluid

This shows you how to add/remove fluid under the mouse/finger. This is done using the FlowPaintScreen component, which allows you to select any FlowModifier in your scene or in a prefab. Keep in mind this component uses a physics raycast to calculate where to apply the modifier, so it won''t land on the fluid surface, only the ground underneath it.

Blood Pooling

This shows you how to emit blood particles that collect on the ground to form a pool of blood. This is done by using a FLOW/Particles shader/material that uses a solid circle texture so it looks like blood droplets. These particles emit a red fluid with a fairly low viscosity value of 0.5, which is low enough to quickly spread out, but high enough to still keep its shape.

Save Load

This shows you how to read and write fluid simulation data to a temporary buffer (erased when you switch scenes or close app). This is done using the FlowSnapshot component, whose SaveToTemp and LoadFromTemp methods can be called from UI buttons. This can also be done manually from code using the FlowSnapshot component or FlowSnapshotData class.

To File

This shows you how to read and write fluid simulation data to a local file. This is done using the FlowSnapshot component, whose SaveToFile and LoadFromFile methods can be called from UI buttons. This can also be done manually from code using the FlowSnapshot component or FlowSnapshotData class.

Ripple

This shows you how to make the water surface ripple when an object passes through the water surface. This is done by adding the FlowSplashSurface component to your floating object, and setting the SplashPrefab setting to the Ripple prefab. This prefab has the FlowSplash component, which applies all attached FlowModifier components to the splash location.

Splash

This shows you how the splash effect emit particles. This is done using the Ripple + Splash prefab, whose Prefabs setting contains the Splash Particles prefab. This prefab has a dormant particle system and the FlowSplashSpawnEmit component, which manually emits particles based on the strength of the splash. This component receives this information via its implementation of the ISplashSpawnHandler interface.

Sample Deepest Point

This shows you how to detect the deepest fluid depth within a specific region of the fluid simulation. This is done by making a new GameObject with the FlowSampleArea component, which will periodically read the underlying fluid simulation depth data. This component has size settings similar to modifiers. You can then add the FlowSampleAreaDeepest component alongside it. This component will invoke the OnDeepestGroundPosition and OnDeepestSurfacePosition events depending on what you need.

Sample Fluid Volume

This shows you how to detect the total volume of fluid within a specific area. This is done by making a new GameObject with the FlowSampleArea component, which will periodically read the underlying fluid simulation depth data. This component has size settings similar to modifiers. You can then add the FlowSampleAreaVolume component alongside it. This component will invoke the OnVolume event, which can be drawn to the screen, etc.

Container

This shows you how to make a modifier emit a specific volume of fluid over time, and then turn off. This is done by adding the FlowContainer component to your scene with the desired fluid Volume & capacity. You can then add the FlowModifierContainer component alongside your FlowModifier, and drag and drop your previously created container into the Container setting.

Overflow

This shows you how to make bigger waves than would normally be possible. This is done by enabling the FlowSimulation component's Physics Model / Overflow setting. This allows you to create FlowModifier components with Mode = AddForce, and very high Strength values. Normally the applied force is clamped to the fluid depth, but enabling this setting allows it to go much higher, which can create more impressive waves.

Island

This shows you how to combine multiple features and have a ship sail around an island, all with a low poly look.

Large

This shows you how fluids can be added to a large 1km\xB2 terrain.

Assets

Here's a list of all my other assets, please check them out!

You can also view this list on my Asset Store page.

Lean Touch

Rapidly develop your game with consistent input across desktop & mobile using Lean Touch. This lightweight asset comes with many modular components, allowing you to customize them to your exact project needs!

Lean Touch+

Lean Touch+ is an extension to the popular Lean Touch asset, adding many more example scenes.

Lean Localization

Lean Localization is a localization library that's designed to be as simple to use as possible for both designers, and programmers.

Lean Pool

Quickly optimize the performance of your games using Lean Pool. Within minutes you can use this lightweight asset to preload, recycle, and limit the spawning of your prefabs.

Lean Transition

Quickly polish your games using Lean Transition. This asset allows you to easily tween or animate almost anything in your game, making it transition smoothly.

Lean GUI

Lean GUI is a colllection of components that extend Unity's GUI system, allowing you to rapidly enhance the user experience (UX) of your game's UI.

Lean GUI Shapes

Lean GUI Shapes allows you to quickly add lines, rounded boxes, polygons, and much more to your GUI!

Lean Texture

Lean Texture allows you quickly modify textures in your project with a range of filters, pack them together into channels, and much more!

Lean Texture+

Lean Texture+ is an extension to Lean Texture, adding many new types of texture modification tools!

Spaceships - Build & Destroy

Build your dream spaceship, and then have fun destroying it!

Modular Backgrounds

Unlock a universe of visual possibilities with Modular Backgrounds. Simply drag and drop these graphics into the background of your scenes.

Paint in 3D

Paint all your objects using Paint in 3D - both in game, and in editor. All features are optimized with GPU accelerated texture painting, so you can enjoy consistent performance, even if you paint your objects one million times!

Paint in 2D

Paint all your sprites with Paint in 2D. With incredible performance on mobile, WebGL, and much more!

Paint in Editor

Paint in Editor unlocks the ability to paint objects in your scene - great for making small tweaks, or even creating entirely new texture sets!

FLOW

FLOW allows you to add large scale interactive fluids to your scene - all highly optimized using GPU acceleration.

Destructible 2D

Unlock the full potential of your 2D games using Destructible 2D, this asset allows you to quickly convert all your boring solid sprites into fully destructible ones!

Space Graphics Toolkit

Quickly make the space scene of your dreams using Space Graphics Toolkit. This huge collection of space effects can be customized and combined in any way you like, allowing you to quickly make realistic or fantasy worlds. Each feature has been heavily optimized to run on almost any device and platform.

Space Graphics Planets

Enhance your space scenes using this large pack of high detail volumetric planets. These planets are finished using the powerful planet features from Space Graphics Toolkit (not required).

Volumetric Audio

Unity sounds only emanate from a single point source. This is great for explosions and footsteps, but quite often you need something more advanced. Volumetric Audio is an easy to use package that allows you to define boxes, spheres, capsules, paths, or meshes that sounds can emanate from.

Versions

2.1.0

Updated CW/Common code to latest version.
Updated shaders to latest version.

2.0.5

Moved main build to Unity 2021.3.0f1.
Updated shaders to latest version.
Fixed FlowModifier component's ColorChannels setting.
Renamed FlowModifier component's ColorChannels setting to Channels.
Added Mode = Change ESMV setting to FlowModifier component.
Added Mode = Range Change ESMV setting to FlowModifier component.

2.0.4

Moved main build to Unity 2020.3.0f1.

2.0.3

Fixed Save Load / To File demo scene.
Fixed fluid snapshot save/load in gamma color space.
Fixed foam increasing opacity even when disabled.
Fixed RemoveFluid modifiers not being able to continuously remove all fluid.

2.0.2

Fixed FlowModifier.MonitorFluidDepth setting.
Added FlowContainer component.
Added FlowModifierContainer component.
Added Container demo scene.
Added FlowSimulation.SimulationOverflow setting.
Added Overflow demo scene.
Added CwRenderTextureManager for alternative RenderTexture creation code.
Removed GC Alloc from FlowWetness component.

2.0.1

Script assembly reload fix for materials.
Added FlowModifier.MonitorFluidDepth setting.
Added FlowModifier.OnFluidDepthDelta event.
Added Sample Deepest Point demo scene.
Added Sample Fluid Volume demo scene.
Improved FlowModifier scene view gizmos.
Removed FlowModifier.HeightMin/Max settings from existing modes.
Added new FlowModifier modes for HeightMin/Max range.

2.0.0

NOTE This is a massive update. To update you must first back up your project, delete the root FLOW folder, then install the new version.

Changed folder structure to be inside Plugins/CW/FLOW.
Updated inspector code to support third party assets that implement nested inspectors.
Replaced FlowModifierSpeed.Angle setting with Rotation.
Improved "Island" demo scene ship wake.
Added FlowSimulation.PhysicsModel setting.
Added FlowSimulation.PhysicsModel / Instability setting.
Added FlowSimulation.PhysicsModel / Damping setting.
Added FlowSimulation.PhysicsModel / Spread setting.
Added FlowSimulation.PhysicsModel / Speed setting.
Replaced FlowDepthMode component with CwDepthTextureMode.

1.0.7

Fixed demo scene errors with certain keyboard layouts.
Added FlowFloat.FluidDrag setting.
Added FlowModifierSpeed.Angle setting.

1.0.6

Fixed shader errors when making WebGL builds.
Fixed shader warnings when making WebGL builds.

1.0.5

Increased FlowTrigger limit.
Added support for the Enviro asset.
Improved linear color space rendering.
Added Ripple demo scene.
Added Ripple / Splash demo scene.
Fixed transform gizmos not appearing in Unity 2021.2.
Fixed ship controls not working in newer versions of the new input system.

1.0.4

Fixed particles disappearing if they fall outside of simulation boundary.
Added Save Load demo scene.
Added Save Load / To File demo scene.

1.0.3

Fixed FLOW / Surface shader transparency breaking at far camera distances with low camera clip distance.
Added Blood Pooling demo scene.
Added Sink setting to FLOW / Surface shader.
Added WAVE / Strength Min setting to FLOW / Surface shader.
Added WAVE / Strength Max setting to FLOW / Surface shader.
Added WAVE / Strength Scale setting to FLOW / Surface shader.
Added TRANSPARENCY / Mode setting to FLOW / Surface shader.
Added TRANSPARENCY / Step setting to FLOW / Surface shader.
Added TRANSPARENCY / Max Steps setting to FLOW / Surface shader.
Added TRANSPARENCY / Depth Scale setting to FLOW / Surface shader.
Added TRANSPARENCY / Mode setting to FLOW / Underwater shader.
Added TRANSPARENCY / Step setting to FLOW / Underwater shader.
Added TRANSPARENCY / Max Steps setting to FLOW / Underwater shader.
Improved the smoothness of viscous fluid flow.
Improved fluid particle radius calculation.

1.0.2

Renamed FlowPaintModifier component to FlowPaintScreen.
Fixed Paint Fluid demo scene touch controls on mobile.
Added Viscosity reading to FlowSample component.
Added Custom1/2/3 settings to FlowFluid component.
Added Advanced / CustomData setting to FlowSimulation component.
Added Advanced / PrecisionA/B/C/D/E/F settings to FlowSimulation component.
Rewrote fluid data storage code to be more flexible and improve precision.
Improved particle simulation performance.

1.0.1

Added Trigger / Fluid demo scene.
Added Paint Fluid demo scene.
Added FlowSample.OnSampledNothing event.
Added FlowSampleFluid component.
Added FlowPaintModifier component.
Fixed gc alloc from FlowSurface component.
Fixed gc alloc from FlowParticles component.
Fixed gc alloc from FlowUnderwater component.

1.0.0

Initial Release.

Components

FlowContainer

This component stores a volume of fluid that can then be filled and emptied via the FlowModifierContainer component.

float
Volume

The volume of fluid stored in this container.

float
Capacity

The maximum volume of fluid that can be stored in this container.

bool
Clamp

Should the Volume be restricted to the 0..Capacity range?

The precise volume of fluid a modifier adds or removes isn't known ahead of time, so it can sometimes be beneficial to allow the Volume value to go slightly below or above the standard range.

FloatEvent
OnVolume

This gets invoked every time the Volume value is changed.

Float = Current Volume.

FloatEvent
OnVolume01

This gets invoked every time the Volume value is changed.

Float = Current Volume / Capacity clamped to 0..1.

void
AddVolume
FlowSimulation simulation, float delta

This method will add fluid to the container.

void
RemoveVolume
FlowSimulation simulation, float delta

This method will remove fluid from the container.

void
AddVolume
float delta

This method will add fluid to the container.

void
RemoveVolume
float delta

This method will add fluid to the container.

FlowContainerTransform

This component will scale the specified

FlowContainer
Container

The container this component will read.

Transform
Target

The Transform this component will modify.

bool
LocalPosition

Should the Target's localPosition be modified?

bool
LocalRotation

Should the Target's localRotation be modified using Euler values?

bool
LocalScale

Should the Target's localPosition be modified?

FlowCrop

This class allows you to crop part of a RenderTexture into a temporary RenderTexture.

FlowEmitter

This component allows you to emit fluid particles into the scene.

FlowFluid
Fluid

This allows you to choose what type of fluid this component emits particles of.

FlowSimulation
Simulation

This allows you to choose which fluid simulation the emitted particles will be added to.

None/null = The closest fluid will be used.

float
VolumeMin

The minimum amount of fluid added to the simulation.

float
VolumeMax

The maximum amount of fluid added to the simulation.

float
SpeedMin

The minimum speed of the emitted particles in world space.

float
SpeedMax

The maximum speed of the emitted particles in world space.

float
LifeMin

The minimum lifespan of the emitted particles in seconds.

float
LifeMax

The maximum lifespan of the emitted particles in seconds.

float
Spread

The particles will fire out in a spread from the forward direction by up to this many degrees.

Vector3
Direction

The particles will emit in this direction in local space.

float
Interval

The time between each particle emission in seconds.

static FlowEmitter
Create
int layer = 0, Transform parent = null

This allows you create a new GameObject with the FlowEmitter component attached.

static FlowEmitter
Create
int layer, Transform parent, Vector3 localPosition, Quaternion localRotation, Vector3 localScale

This allows you create a new GameObject with the FlowEmitter component attached.

FlowFadeOut

This component fades out the first material's Color.a to 0.

float
Duration

The time the fade out takes in seconds.

float
Opacity

The maximum opacity that will be faded from.

UnityEvent
OnFinished

This event is invoked when the fade out finishes.

FlowFloat

This component allows you to make a Rigidbody float in a fluid.

List<FlowSample>
Samples

This object's buoyancy will be calculated using these height samples.

float
Buoyancy

The buoyancy of this object.

0 = Sinks.

1 = Neutral.

2 = Floats.

float
Drag

The positional drag of this object while underwater.

float
FluidDrag

This allows you to control how much the fluid velocity is involved in the drag calculation. For most objects this should be set to 1, but if your object applies force to the fluid then you can end up with scenarios where the object causes itself to accelerate, so reducing this can counteract that.

float
AngularDrag

The rotation drag of this object while underwater.

NOTE If you have multiple sample points then this setting may be unnecessary, because the sample points will work together to slow the object's rotation.

float
Torque

This setting tries to turn the object upwards when underwater. This is useful for boats, buoys, and other objects that should remain upright. Similar behavior can be achieved with many sample points, but that can be difficult to set up and have negative performance impact.

TorqueType
TorqueMode

This allows you to control how the Torque setting will apply.

WorldUp = Rotate to face up.

WorldUpBidirectional = Rotate to face up or down.

NormalUp = Rotate up to fluid surface.

NormalUpBidirectional = Rotate up or down to fluid surface.

void
ResetSamples

This will automatically reset the Samples list based on any child GameObjects that contain a FlowSample.

FlowFluid

This component allows you to define fluid properties.

Color
Color

The color of this fluid.

float
Emission

The emission of this fluid.

float
Smoothness

The PBR smoothness of this fluid.

float
Metallic

The PBR metallic of this fluid.

float
Viscosity

The viscosity of this fluid.

float
Custom1

The first custom property of this fluid.

NOTE To use this, your FlowSimulation component's Advanced / CustomData setting must be set to One or Three.

float
Custom2

The second custom property of this fluid.

NOTE To use this, your FlowSimulation component's Advanced / CustomData setting must be set to Three.

float
Custom3

The third custom property of this fluid.

NOTE To use this, your FlowSimulation component's Advanced / CustomData setting must be set to Three.

FlowFormatString

This component allows you to convert values like ints and floats into formatted text that can be shown in the UI. To use this component, simply call one of the SetString methods, and it will output the formatted string to the OnString event, which can be connected to UI text, etc.

string
Format

The final text will use this string formatting, where {0} is the first value, {1} is the second, etc. Formatting uses standard string.Format style.