In opengl ES can I use a vertex buffer array buffer etc for shader shared matrices?

Question

As OpenGL ES does not support shared "uniform blocks" I was wondering if there is a way I can put matrices that can be referenced by a number of different shaders, a simple example would be a worldToViewport or worldToEye which would not change for an entire frame and which all shaders would reference. I saw one post where one uses 3 or 4 dot calls on a vertex to transform it from 4 "column vectors", but wondering if there is a way to assign the buffer data to a "mat4" in the shader.

Ah yes the need for this is webGL which at the moment it seems only to support openGLES 2.0.

I wonder if it supports indexed attribute buffers as I assume they don't need to be any specified size relative to the size of the position vertex array.

Then if one can use a hard coded or calculated index into the attribute buffer ( in the shader ) and if one can bind more than one attribute buffer at a time, and access all "bound to the shader" buffers simultaneously in a shader ...

I see if all true might work. I need a good language/architecture reference on shaders as I am somewhat new to shader programming as I I'm trying to deign a wall without knowing the shapes of the bricks :)

Answer 1

Vertex attributes are per-vertex, so there is no way so share vertex attributes amongst multiple vertices.

OpenGL ES 2.0 upwards has CPU-side uniforms, which must be uploaded individually from the CPU at draw time. Uniforms belong to the program object, so for uniforms which are constant for a frame you only have to modify each program once, so the cost isn't necessarily proportional to draw count.

OpenGL ES 3.0 onwards has Uniform Buffer Objects (UBOs) which allow you to load uniforms from a buffer in memory.

I'm not sure what you mean by "doesn't support shared uniform blocks", as that's pretty much what a UBO is, albeit it won't work on older hardware which only supports OpenGL ES 2.x.