draw_cubemap.glsl

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#version 330
 
#ifdef VERTEX_SHADER
 
void main( )
{
    // repere projectif
    vec2 positions[3]= vec2[3]( vec2(-1,-1), vec2(3, -1), vec2(-1, 3) );
    // place le point sur le plan far / z=1... a l'infini
    gl_Position= vec4(positions[gl_VertexID], 1, 1);
}
#endif
 
#ifdef FRAGMENT_SHADER
 
uniform mat4 invMatrix;
uniform vec3 camera_position;
uniform samplerCube texture0;
 
out vec4 fragment_color;
 
void main( )
{
    vec4 p= invMatrix * vec4(gl_FragCoord.xyz, 1);
    vec3 pixel= p.xyz / p.w;
    
    vec3 direction= normalize(pixel - camera_position);
    fragment_color= texture(texture0, direction);
}
#endif