DrawMeshInstanced option to provide per instance material property block?

I have an array of transformation matricies, and an array of material property blocks (one for each matrix)

In 5.4, I can do this:

Code (CSharp):

1. for (int i = 0; i < matrixList.Count; i++)
2. {
3.        Graphics.DrawMesh(someMesh, matrixList[i], someInstancedMaterial, someLayer, null, 0, matPropertyBlockList[i]);
4. }

This works as expected. My mesh gets draw multiple times, each instance is draw with custom properties, and the result is only 1 draw call. (Instanced batching)

In 5.5, this does not work. I have a separate post regarding this here, maybe this is a regression/bug.

Let's ignore that for a sec. 5.5 provides a new method - DrawMeshInstanced. It takes an array of matricies but only takes a single material property block. From what I can see, the only difference between DrawMeshInstanced and DrawMesh is that I do not have to call DrawMesh hundreds of times. Instead, I can create an array of matricies with hundreds of elements, and call DrawMeshInstanced a single time with all the information. However, DrawMeshInstanced only takes a single material property block, so that means that every instance needs to use the same data!

I think it is necessary to have a DrawMeshInstanced method that takes an array of material property blocks too, so that we can achieve the same thing as above with a single line:

Code (CSharp):

1. Graphics.DrawMeshInstanced(someMesh, matrixArray, someInstancedMaterial, someLayer, null, 0, matPropertyBlockArray);

As a side note, I wanted to mention that 'Graphics.DrawMesh' (5.4) seems to know how to split up draw calls by itself. It only batches 500 instances together before splitting it out to a second draw call. In contrast to this, 'Graphics.DrawMeshInstanced' simply complains with an error log if you pass it a matrix array with more than 1023 elements and doesn't draw anything. Couldn't this just be handled internally, as with Graphics.DrawMesh in 5.4?

 

You can use arrays in your MaterialProperyBlock and use the instance id in your shaders to index into the arrays.

 

Sounds like a work around? In 5.4 I did not have to deal with arrays and indexing in to arrays in my shader at all. I had MaterialPropertyBlock for each object, and simply passed that along to DrawMesh and it worked fine.

Using your method, I can't get the built in Standard Shader (Instanced) to work correctly with a custom color for each instance. It sounds like your suggestion is fundamentally different to what normally happens in the instancing pipeline.

Also I noticed that MaterialPropertyBlock complains when you try to create an array large than 1023 elements, which was a non issue with per-instance MaterialPropertyBlock's.

 

Thanks for the clarification and update! Looking forward to it.