1void main() { 2 gl_Position = gl_Vertex; 3 vec4 sum = vec4(0); 4 for (int i = 1; i != 2; i += 2) { 5 sum += vec4(0.1, 0.1, 0.1, 0.1); 6 } 7 gl_FrontColor = sum; 8} 9