Question LinearBlendSkinning node & Graphics.DrawMesh?

Hi,

I have a dumb question :/

Is there a way to combine Graphics.DrawMesh() and Linear blend skinning node?

Linear blend skinning documentation says "You must provide skinned matrices in the _SkinMatrices buffer. The node uses the _SkinMatrixIndex property to calculate where the matrices associated with the current mesh are located in the _SkinMatrices buffer."

Is it possible to call Graphics.DrawMesh(), and feed in the SkinMatrices?

Code (CSharp):

1. public static void DrawMesh(
2. Mesh mesh,
3. Vector3 position,
4. Quaternion rotation,
5. Material material /*Use a LinearBlendSkinning material*/,
6. int layer,
7. Camera camera = null,
8. int submeshIndex = 0,
9. MaterialPropertyBlock properties = null /*Provide SkinMatrices somehow??*/,
10. bool castShadows = true,
11. bool receiveShadows = true,
12. bool useLightProbes = true
13. );
14.  

 

Do not answer all at the same time!?

 

The skin matrices are stored in a global compute buffer and the shader uses a hybrid instanced property to index the buffer.

May I ask why you are trying to use DrawMesh for a DOTS skinned mesh?

 

Just to experiment.

Does that mean it is possible to animate mesh called from DrawMesh()? If so, can you tell me in theory how would it work?

 

I have no idea if this is possible, but if it is, here is what you need to do:
First, you need to fill a ComputeBuffer with the skin matrices of your bones in the format the shader expects. This is likely a float3x4 but you should probably check your version to make sure. Assign that buffer to the global _SkinMatrices property.
Second, you need to set the _SkinMatrixIndex property to be the first index of your skeleton. That may or may not be possible since normally this is a DOTS instanced property.

 

Hi,

I just tested it, did not work. My character stays T pose.

Unless I have made some mistakes? See code below.

Code (CSharp):

1.     private void Start()
2.     {
3.         propetyBlock = new MaterialPropertyBlock();
4.  
5.         computeBuffer = new ComputeBuffer(skinMatrix.Count, sizeof(float) * 12, ComputeBufferType.Constant);
6.         computeBuffer.SetData<float3x4>(skinMatrix);
7.  
8.         propetyBlock.SetInt("_SkinMatrixIndex", 0);
9.         propetyBlock.SetBuffer("_SkinMatrices", computeBuffer);
10.     }
11.  
12.     private void Update()
13.     {
14.         Graphics.DrawMeshInstanced(
15.             mesh,
16.             0,
17.             material,
18.             new Matrix4x4[] {Matrix4x4.TRS(new Vector3(0,0,0), Quaternion.identity, new Vector3(0.01f, 0.01f, 0.01f))},
19.             1,
20.             propetyBlock
21.             );
22.     }

List<float3x4> skinMatrix that I provided in computeBuffer.SetData() is a running pose... but he stays in T pose.

propetyBlock.SetInt("_SkinMatrixIndex", 0); this should alway be 0 right? because index 0 is my root bone.

 

What you are feeding in seems correct. But the API you are using to feed in the data must not be correct, which is the issue I suspected you may run into.

Unfortunately I can't really tell you the right way to set the data. Personally, I let the Hybrid Renderer populate _SkinMatrixIndex and use Shader.SetGlobalBuffer for _SkinMatrices (actually I use the Compute Deformation equivalents). I also disabled Hybrid Renderer's built-in skinning so that it doesn't overwrite the buffer assignments.

 

Thanks for your help, maybe someone else will be able to tell me the right way to do it?