GLSL统一数组的值不正确

Question

I am trying to pass light and lightcolor information to my shader via a uniform array. I declared these in my shader like this:

     uniform vec2 lightpositions[4];
     uniform vec4 lightcolors[4];

And in my code (C++):

float lightpositions[8] = { 
        150, 150,
        (float) screenWidth - 150, 150,
        (float) screenWidth - 150, (float) screenHeight - 150,
        150, (float) screenHeight - 150
};

float lightcolors[16] = {
        1.0, 0.0, 0.0, 1.0,
        1.0, 1.0, 0.0, 1.0,
        1.0, 0.0, 1.0, 1.0,
        0.0, 1.0, 1.0, 1.0
};

glUniform2fv(lightposHandle, amount, lightpositions);
checkGlError("lightPositions");

glUniform4fv(lightcolorHandle, amount, lightcolors);
checkGlError("lightColors");

Where amount is 4 in this case.

When I check my OpenGL ES debugger (PerfHud ES) I see that the values in the arrays are almost random like 1.4e+02.

Am I doing something wrong? Or should I use attributes in this case?

Answer 1

Your shader is looks correct (see section 4.1.9 of the "ESSL specification" for a very similar declaration) and so does your API code.

My best guess is that is that something goes wrong when you query the uniform locations, and one or more of the locations are returned as -1. Try checking after each call to glGetUniformLocation if -1 was returned.

(The names used in the calls to glGetUniformLocation in the drawing code you posted do not match the shader code in your questions. This could be the bug you're looking for.)

Answer 2

Allright I solved it.

I created my arrays in a class which I then passed to my Lights class via the constructer. Where my light class assigns this array to a private float* lightpositions. This was the source of the wrong values, because I think (if someone could make this clear) that I was passing in the address of the array. When I create a normal array (float test[8]) the values passed to the shader are correct.

Answer 3

You can not use array notation like this in OpenGL ES 2.0 shader code. That is a 3.0 feature.

Also, I would try it on another platform with different OpenGL ES drivers. You might also need the precision specifiers, like this:

uniform highp vec2 lightpositions[4];
uniform highp vec4 lightcolors[4];

For OpenGL ES 3.0, you would need to construct the array as an array of vec3, like this:

vec3 lightcolors[6] = 
{ 
    vec3(1.0f, 0.0f, 0.0f), vec3(0.0f, 1.0f, 0.0f), vec3(0.0f, 0.0f, 1.0f), 
    vec3(1.0f, 1.0f, 0.0f), vec3(1.0f, 0.0f, 1.0f), vec3(0.0f, 1.0f, 1.0f) 
};