// GL Shading Language version 1.0 Fragment Shader
//  Orion Sky Lawlor, olawlor@acm.org, 2006/08/31 (Public Domain)

// Vertex/fragment shader interface
varying vec4 color; // Material diffuse color
varying vec3 normal; // Surface normal

// Input: from vertex.txt.  Output: gl_FragColor.
void main(void)
{
	vec3 N=normalize(normal);
	
	vec3 L1=normalize(vec3(0,1,0)); /* +Y direction */
	vec4 C1=vec4(1,1,1,1); /* white light */
	vec4 diffuse1=C1*clamp(dot(N,L1),0.0,1.0);
	
	vec3 L2=normalize(vec3(1,0,0)); /* +X direction */
	vec4 C2=vec4(1,0,0,1); /* red light */
	vec4 diffuse2=C2*clamp(dot(N,L2),0.0,1.0);
	
	gl_FragColor=diffuse1+diffuse2; /* total color is sum of light sources */
	gl_FragColor.a=1.0; /* Force object to be opaque */
}