Computations in GPU Unity

Question

I've made a fluid simulation using particles in Unity, but now it is painfully slow because all computations are done using the CPU. In order to make it faster, I need to do computations on the GPU, and I learned that I would have to use compute shaders for that.

The problem is, to make a fluid simulation, I need to make and track each particle and perform collisions on each of them on a certain time interval, and I don't understand how this could be achieved using shaders when the concept of shaders (from what I currently understand) is performing calculations on one already made mesh. Also, I'm using prebuilt physics calculations (rigidbody) in Unity, and would using shaders mean that I would not be able to use these?

How can I make this effect more efficient?

Answer 1

Create a compute shader in Unity and write your particle update logic (e.g., position, velocity, collision detection, and response) in the shader code.

Store your particle data in StructuredBuffers or other appropriate buffer types. You will need to create a buffer for the particle positions, velocities, and any other properties you need to track in the simulation.

In your C# script, create and configure the necessary buffers to hold particle data and pass them to the compute shader using the SetBuffer method.

Dispatch the compute shader by invoking the Dispatch method in your C# script. You'll need to specify the number of threads to run in parallel, which should be configured to best match your GPU's capabilities.

After the compute shader finishes executing, retrieve the updated particle data from the buffers in your C# script.

Use the updated particle data to update the positions of your particles in the scene. You can either use the Graphics.DrawMeshInstanced method to render the particles as meshes or update the positions of ParticleSystem particles.