I have WebGL code running hardware skinning in a vertex shader for animations, using a uniform array of matrices for my bones.

The problem arises when I don't have enough vector slots, which happens when there are more than 62 bones (I don't control the models or the number of bones, and I've already seen a model with 173 bones, which is crazy).

I tried using a float texture to store all my bones in, and fetch them in the shader, but I can't seem to do that correctly.

There is no texelFetch in WebGL's version of GLSL, no 1D textures and obviously no texture buffers or uniform buffers.

What I tried was creating a X on 1 2D float texture, where X is the number of floats required for all the matrices, feeding it with all the matrices.

I send to the shader the size of each matrix and the size of each vector, relative to the size of the texture, so I can get to any matrix with a normal texture fetch.

I believe this should work...in theory. But it doesn't.

This is the texutre initialization code:

var buffer = new Float32Array(...); ... gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, buffer.byteLength / 16, 1, 0, gl.RGBA, gl.FLOAT, buffer); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);

And the part of the vertex shader that constructs a matrix from the texture, given a matrix index:

... uniform sampler2D u_bone_map; uniform float u_matrix_fraction; uniform float u_vector_fraction; ... mat4 boneMatrix(float bone) { return mat4(texture2D(u_bone_map, vec2(u_matrix_fraction * bone, 0)), texture2D(u_bone_map, vec2(u_matrix_fraction * bone + u_vector_fraction, 0)), texture2D(u_bone_map, vec2(u_matrix_fraction * bone + u_vector_fraction * 2.0, 0)), texture2D(u_bone_map, vec2(u_matrix_fraction * bone + u_vector_fraction * 3.0, 0))); } ...

u_matrix_fraction and u_vector_fraction are the relative sizes I wrote above.

E.g., if the texture is 512x1 each matrix is 16/512, and each vector is 4/512, so to get the ith matrix, the code would need to go to i*u_matrix_fraction and grab 4 texels, each the size of u_vector_fraction.

These matrices result in my meshes going crazy, so something is wrong, but I am just not sure what.

Got any ideas?

Thanks for any help.

**Edited by Chananya Freiman, 30 June 2013 - 07:12 PM.**