Games GPU Computed Grass Renderer

Hello everyone,

After a endless fight with unity's terrain system i decided to approach the basics of compute shading so i could build my own renderer.

After a couple of days i have to say that im very impressed of the possibilities you can achieve with this fully GPU computed Workflows.

I want to show you my current WIP.
All grass billboards are computed at runtime via a compute shader.
The compute shader fills a AppendStructuredBuffer with thousands of 4x4 matrices.
Also the compute shader gets some height normal color and splat information which i could not bake at runtime.

Fortunately Unity has implementet the DrawMeshInstancedIndirect Method which allows me to beam the buffer directly to the instance shader of the grasses.


This was my first try. I tried to debug the computed Buffer-data with Gizmos.

I tried to add a bit of noise and combine the computed data with an GPU instance Shader.

After a while of experimenting i created a Cell structure to Compute them as parts and cull them.

A "Height" and "Normal" map of course so i don't need to stay flat. ^^

 

Looks good. You can easy add the frustrum planes to the compute shader and do per item frustum culling in a compute shader pass. Will save you the extra GPU time on partial visible cells

 

And now the results of one week

hope you like it

 

Multi terrain support and Debug view ^^

 

The Problem is that i do not update the Compute buffer every frame, but just once it is in View Distance.
But i will test this, thanks a lot!

 

You keep your buffer and just process this every time to a visible buffer that you render with drawMeshInstanced Indirect. I will send you a link to a video where I do this.

 

Awesome!
Maybe one Day i can help you with something

 

Grass is looking good

 

here is a short clip.

sorry for the bad quality.
Runs on a 560GTX.

12.4 ms on CPU
1.1 ms on GPU

It looks like i have to improve the Memory Alloc.

 

@moxi : what is the target level of your shader ? Would it run on a mobile platform (if that's the only thing displayed onscreen) ?

 

Well, i have not tested jet.
But i'm pretty sure it does since you don't need that much bandwidth between the GPU and the CPU as with conventional techniques. As long the Device supports the Vulkan or Metal or OpenGL ES 3.1.

But please do not get me wrong.
Because I don't have plans to Distribute it on the store, since i don't want to compete my work with Mr. Johansen who create wonders with Vegetation Studio.
I pretty sure VS performs way better.

I would say: Testing Time!!!!!

 

As you can see if i fixed the memory Problem

 

Some soothing pics at the end of the day

 

Shader model 5.0 since you use compute shaders.

 

Errmmm, will we ever be able to give this a go ourselves ? Did you say multiterrain support, can you point this in aeras?