MaterialPropertyBlock + shader keywords

Is there any way to enable/disable shader keywords when rendering with Graphics.DrawMesh? I don't see anything in MaterialPropertyBlock, is there another way to do it?

 

Shader keywords are used by the shader compiler to internally generate multiple different shaders. You can think of doing Material.EnableKeyword() as being the same thing as Material.SetShader() at least as far as the GPU is concerned. Material property blocks can only set values that are passed to a shader, not change the shader itself.

 

I'm aware that EnableKeyword selects a shader variant, maybe I should rephrase my question: I'm looking for a way to render different meshes with different variants of a shader, without creating copies of the material for all the combinations (3x3x2=18 versions). Is there a way to do that?

 

No, different shaders or shader variants require the use of different materials.

You can let Unity generate a new material instance per renderer at runtime with renderer.material.EnableKeyword(), or pre-allocate them, or a handful of similar method. Ultimately you will end up with multiple materials.

Depending on what you're doing it might be worthwhile to not use shader variants and just use if statements in the shader if you want to reduce the number of variants. But if you're trying to avoid multiple materials for reasons of draw call reduction unless you are using Unity 5.4 and your shaders are setup for instancing those material property blocks are still going to add draw calls.