glCreateProgram().uniform in python

Question

I am trying to port some javascript code with opengl to python. But cannot figure out what I am doing wrong in translating prog.uniform[u] = gl.getUniformLocation(prog, u);

Javascript:

let v = buildShader(vert, gl.VERTEX_SHADER);
let f = buildShader(frag, gl.FRAGMENT_SHADER);
let prog = gl.createProgram();
gl.attachShader(prog, v);
gl.attachShader(prog, f);
gl.linkProgram(prog);
prog.uniform = {};
u = ['model','bounds','frac','aspect'];
_.each(u, function(u){ prog.uniform[u] = gl.getUniformLocation(prog, u); });

Python3/PyOpenGl:

v = self.buildShader(vert, GL_VERTEX_SHADER)
f = self.buildShader(frag, GL_FRAGMENT_SHADER)
prog = glCreateProgram()
glAttachShader(prog, v)
glAttachShader(prog, f)
glLinkProgram(prog)
for u in ['model','bounds','frac','aspect']:
  loc = glGetUniformLocations(prog,u)
  glProgramUniform(prog,loc,u)

Rabbid76 · Accepted Answer · 2018-11-24 17:31:19Z

3

glProgramUniform assigns a value to a uniform, where the 3rd paramter is the value.

glProgramUniform(prog,loc,u) makes not any sense, when u is string which is the name name of the uniform.

You have to create a dictionary which contains the locations of a uniform for each name:

uniform = {}
for u in ['model','bounds','frac','aspect']:
    uniform[u] = glGetUniformLocation(prog, u)

or simply

uniform = { u : glGetUniformLocation(prog, u) for u in ['model','bounds','frac','aspect'] }

edited Nov 24, 2018 at 17:31

answered Nov 24, 2018 at 16:58

Rabbid76

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4 Comments

Nard Over a year ago

Thx, how to port the prog.uniform[u]= part to python3?

Rabbid76 Over a year ago

@Nard No way, because in python prog is t name of the shader program object, which is just a number. You have to create a tuple (prog, uniform).

Nard Over a year ago

Stupid question probably, but then how do I pass the uniform-variable to opengl or is this not what is happening in the js-code prog.uniform[u] = ?

Rabbid76 Over a year ago

@Nard No prog.uniform[u] doesn't assign anything to uniform variable on the GPU in WebGL (not OpenGL). This is done by gl.Uniform*

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