Using a different vertex and fragment shader for each object in webgl

Question

I have a scene with multiple objects in webgl. For each object I want to use a different vertex and a fragment shader. My first question is, is it possible to have a shader for each object? I am aware it is possible in opengl.

This is something similar pseudo code of what I had in mind. Any example would be much appreciated.

glenableshader
draw triangle
gldisableshader

glenableshader
draw square
gldisableshader

Thank you

Answer 1

You can look up pretty much any WebGL example and turn it into a multiple shader example.

Pseudo code

// At init time
for each shader program
    create and compile vertex shader
    create and compile fragment shader
    create program and attach shaders
    link program
    record locations of attributes and uniforms

for each model/set of geometry/points/data 
    create buffer(s) for model
    copy data into buffer(s) for model

for each texture
    create texture
    usually asynchronously load textures

// at draw time
clear

for each model
   useProgram(program for model)
   setup attributes for model
   setup textures for model
   set uniforms for model
   draw

This is no different than drawing 1 model with 1 shader program. Just do the same setup.

a little more code...

For setting up attributes would look something like

for each attribute used by model
   gl.enableVertexAttribArray(attribLocation);
   gl.bindBuffer(gl.ARRAY_BUFFER, bufferWithDataForAttribute);
   gl.vertexAttribPointer(attribLocation, ...);

Setting up textures (might) look something liek this

for each texture used by model
   gl.activeTexture(gl.TEXTURE0 + ndx);
   gl.bindTexture(gl.TEXTURE_2D, texture);

Finally you'd use the program

gl.useProgram(programForModel);
for each uniform
   gl.uniform???(uniformLocation, uniformValue);

gl.drawArrays(...) 
or 
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, bufferOfIndicesForModel);
gl.drawElements(...);