Simple GLSL program crashes

OpenGL
1

I was trying to debug a problem with a bump mapping shader, when I was surprised when my simple glsl code for debug did not work.

The following code crashes:




uniform sampler2D diffuse_map;

uniform sampler2D normal_map;


varying vec3 lightVec;
varying vec3 halfVec;
varying vec3 eyeVec;


void main (void)
{


        gl_FragColor= vec4(texture2D (normal_map, gl_TexCoord[0].st).rgb, 1.0);

}

But this other code did not:


uniform sampler2D diffuse_map;
uniform sampler2D normal_map;

varying vec3 lightVec;
varying vec3 halfVec;
varying vec3 eyeVec;


void main (void)
{
        vec2 texCoords;

      
       
        texCoords = gl_TexCoord[0].st;
        


        // fetch normal from normal map, expand to the [-1, 1] range, and normalize
        vec3 normal = 2.0 * texture2D (normal_map, gl_TexCoord[0].st).rgb - 1.0;
        normal = normalize (normal);

                // compute diffuse lighting
        vec3 diffuse = max (dot (lightVec, normal), 0.0) * vec3 (gl_LightSource[1].diffuse);
        vec3 decalColor = texture2D (diffuse_map, texCoords).rgb;

        // compute specular lighting
        //vec3 specularCoeff = texture2D (glossMap, texCoords).rgb;
        float specular = max (dot (halfVec, normal), 0.0);
        specular = pow (specular, 8.0);
        
        // output final color
        gl_FragColor = vec4 (diffuse * decalColor + vec3 (specular), 1.0) + gl_LightSource[1].ambient;
}
2

Have you tried removing the unused uniforms and varyings?

Regards,
Patrick

3

Thanks pjcozzi, I needed to clean not only the fragment shader, but also the vertex shader for this piece to run.

This seems very inefficient for testing purposes. I tried only changing the last line of the shader that compiled, like:


gl_FragColor= vec4(decalColor, 1.0);

But it made it crash. Very strange, seems like the GLSL compiler is discarding everything not used and thus giving a problem with the parameters being passed from the CPU. This is the only possibility I can think.

4

I bet that is exactly what is happening. If your GLSL code does not use a uniform, the uniform is optimized out, and it not part of the “active uniforms.” From the perspective of your application, the shader program doesn’t even have the uniform.

Regards,
Patrick

5

Good to know I am not alone on that.

If there was an way to compile the GLSL code without optimizations… that would be nice for debugging!

6

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