/*
 * lighting.frag
 *
 * Lighting calculations
 *
 * (c) 2007-2008 Thomas White <taw27@cam.ac.uk>
 *
 *  thrust3d - a silly game
 *
 */

varying vec3 pos;
varying vec3 normal;

varying vec3 light0vc;
varying vec3 light0half;
varying vec3 light1vc;
varying vec3 light2vc;
varying vec3 light2hvc;

uniform sampler2D texture;
uniform sampler2D normalmap;

uniform bool has_normals;
uniform bool fill_light_enabled;
uniform bool texture_enabled;
uniform bool texture_emits;
uniform float alpha;

varying vec3 col_ambi_diff;
varying vec3 col_emit;

void main() {
	
	vec3 ambi;
	vec3 emit;
	vec3 diff = vec3(0.0, 0.0, 0.0);
	vec3 spec = vec3(0.0, 0.0, 0.0);
	vec3 norm = normal;
	
	if ( has_normals ) {
		norm += (texture2D(normalmap, gl_TexCoord[0].st).rgb - vec3(0.5, 0.5, 0.5)) / 2.0;
	}
	
	norm = normalize(norm);
	
	/* Ambient */
	ambi = col_ambi_diff * gl_LightModel.ambient.rgb;
	
	/* Emission */
	emit = col_emit;
		
	/* Fill-in light (light 2) */
	if ( fill_light_enabled ) {
		
		float ndothv;
		
		ndothv = max(dot(norm, normalize(light2hvc)), 0.0);
		diff += col_ambi_diff * gl_LightSource[2].diffuse.rgb * max(dot(vec3(light1vc), norm), 0.0);
		spec += gl_LightSource[2].specular.rgb * pow(ndothv, 80.0);

	} else {
	
		/* Spotlight (light 0) - positional, spotlight */
		float falloff, spot;
		float spec_fac;
		vec3 L, E, R;
		
		falloff = 1.0 / (  gl_LightSource[0].constantAttenuation
			            + gl_LightSource[0].linearAttenuation * length(light0vc)
			            + gl_LightSource[0].quadraticAttenuation * pow(length(light0vc), 2.0) );
		spot = max(dot(normalize(-light0vc), gl_LightSource[0].spotDirection), 0.0);
		spot = pow(spot, gl_LightSource[0].spotExponent);
		
		L = normalize(gl_LightSource[0].position.xyz - pos); 
		E = normalize(-pos);
		R = normalize(-reflect(L, norm)); 
		
		spec_fac = max(0.0, dot(R, E));
		
		diff += col_ambi_diff * gl_LightSource[0].diffuse.rgb * spot * falloff *
									max(dot(normalize(light0vc).xyz, norm), 0.0);
		
		spec += vec3(1.0, 1.0, 1.0) * gl_LightSource[0].specular.rgb * spot * falloff * pow(spec_fac, 80.0);
		
		/* Background glow (light 1) - diffuse only, directional */
		diff += col_ambi_diff * gl_LightSource[1].diffuse.rgb * max(dot(vec3(light1vc), norm), 0.0);

	}
	
	if ( texture_enabled ) {
	
		vec3 tex = texture2D(texture, gl_TexCoord[0].st).rgb;
		
		if ( texture_emits ) {
			gl_FragColor = vec4(tex.r, tex.g, tex.b, alpha);
		} else {
			gl_FragColor = vec4(min(tex.r * (ambi.r + diff.r) + spec.r, 1.0),
					    min(tex.g * (ambi.g + diff.g) + spec.g, 1.0),
					    min(tex.b * (ambi.b + diff.b) + spec.b, 1.0),
					    alpha);
		}
	
	} else {

		gl_FragColor = vec4(min(emit.r + ambi.r + diff.r + spec.r, 1.0),
				    min(emit.g + ambi.g + diff.g + spec.g, 1.0),
				    min(emit.b + ambi.b + diff.b + spec.b, 1.0),
				    alpha);

	}

}