#define TAU 6.283185307179586

varying vec2 v_vTexcoord;
varying vec4 v_vColour;

uniform vec2 dimension;
uniform vec2 center[4];
uniform vec3 color[4];
uniform vec4 strength;

uniform int blend;

void main() {
	vec4 distances = vec4(0.);
	float maxDist = 0.;
	int i;
	
	for( i = 0; i < 4; i++ ) {
		float d      = distance(v_vTexcoord, center[i] / dimension);
		distances[i] = d;
		maxDist      = max(maxDist, d);
	}
	
	maxDist *= 2.;
	
	for( i = 0; i < 4; i++ )
		distances[i] = pow((maxDist - distances[i]) / maxDist, strength[i]);
	
	vec4 weights;
	
	     if(blend == 0) weights = distances / (distances[0] + distances[1] + distances[2] + distances[3]);
	else if(blend == 1) weights = normalize(distances);
	
	vec3 clr = color[0] * weights[0] + 
	           color[1] * weights[1] + 
			   color[2] * weights[2] + 
			   color[3] * weights[3];
	
	gl_FragColor = vec4(clr, 1.);
}