Question

In the vertex shader I define a structure:

#version 110                                                                 
struct LightSourceParameters {                                               
    vec4 ambient;                                                            
    vec4 diffuse;                                                            
    vec4 specular;                                                           
    vec4 position;                                                           
};                                                                           

and declare an instance for a single light

uniform LightSourceParameters light;                                         

but when I try to get a parameter of the light, it fails ( i < 0 )

name = "light.ambient"                                                       
GLint i = glGetUniformLocation(program, name );                              
// i == -1                                                                   

I know I cannot refer structures, but here I refer an exact field. What can be wrong?
~

Answer 1

Are you using that structure in the shader? If not, then the compiler is well within its rights to optimize the uniform out.