OpenGL ES 2.0 Vertex skinning maximum number of bones?

Question

When drawing a vertex skinned model, what is the maximum number of bones per draw-call/batch for different iOS devices?

On OpenGL ES 1.1 the limit is set by the number of palette matrices, but how about OpenGL ES 2.0, what sets the limit?

Answer 1

OpenGL ES 2.0 uses shaders for all of its vertex processing. So it depends on how many uniform matrices you can create. This is an implementation-defined limit, so it varies from hardware to hardware.

You can also use quaternions+position for bones instead of full matrices to save space.

Answer 2

From iOS 7 you can access the texture units from the vertex shader, so you can make a texture, fill it with your matrices and access the matrices from your vertex shader. This will allow many more matrices to be accessed, at the expense of a more complex implementation.