// light position and geometry normal
float phong_weightCalc( in vec3 light_pos, in vec3 frag_normal ) 
{
	// returns vec2( ambientMult, diffuseMult )
	float n_dot_pos = max( 0.0, dot( frag_normal, light_pos	) );
	return n_dot_pos;
}

uniform vec4 Global_ambient;
uniform vec4 Light_ambient;
uniform vec4 Light_diffuse;
uniform vec3 Light_location;
uniform vec4 Material_ambient;
uniform vec4 Material_diffuse;
attribute vec3 Vertex_position;
attribute vec3 Vertex_normal;
varying vec4 baseColor;

void main() {
	gl_Position = gl_ModelViewProjectionMatrix * vec4( Vertex_position, 1.0 );
	vec3 EC_Light_location = gl_NormalMatrix * Light_location;
	float diffuse_weight = phong_weightCalc( normalize(EC_Light_location), 
											 normalize(gl_NormalMatrix * Vertex_normal) );
	baseColor = clamp(
	(
		// global component
		(Global_ambient * Material_ambient)
		// material's interaction with light's contribution
		// to the ambient lighting...
		+ (Light_ambient * Material_ambient)
		// material's interaction with the direct light from
		// the light.
		+ (Light_diffuse * Material_diffuse * diffuse_weight)
	), 0.0, 1.0);
}