#define TAU 6.28318530718

varying vec2 v_vTexcoord;
varying vec4 v_vColour;

uniform vec2  dimension;
uniform vec2  pos1;
uniform vec2  pos2;
uniform float radius;
uniform float intensity;
uniform float falloff;

#region /////////////// SAMPLING ///////////////

	const float PI = 3.14159265358979323846;
	uniform int  interpolation;
	uniform vec2 sampleDimension;
	
	const int RSIN_RADIUS = 1;
	
	float sinc ( float x ) { return x == 0.? 1. : sin(x * PI) / (x * PI); }
	
	vec4 texture2D_bilinear( sampler2D texture, vec2 uv ) {
		uv = uv * sampleDimension - .5;
		vec2 iuv = floor( uv );
		vec2 fuv = fract( uv );
		
		vec4 mixed = mix(
			mix(
				texture2D( texture, (iuv + vec2(0., 0.)) / sampleDimension ),
				texture2D( texture, (iuv + vec2(1., 0.)) / sampleDimension ),
				fuv.x
			), 
			mix(
				texture2D( texture, (iuv + vec2(0., 1.)) / sampleDimension ),
				texture2D( texture, (iuv + vec2(1., 1.)) / sampleDimension ),
				fuv.x
			), 
			fuv.y
		);
		
		mixed.rgb /= mixed.a;
		
		return mixed;
	}
	
	vec4 texture2D_rsin( sampler2D texture, vec2 uv ) {
	    vec2 tx = 1.0 / sampleDimension;
	    vec2 p  = uv * sampleDimension - vec2(0.5);
	    
		vec4 sum = vec4(0.0);
	    float weights = 0.;
	    
	    for (int x = -RSIN_RADIUS; x <= RSIN_RADIUS; x++)
		for (int y = -RSIN_RADIUS; y <= RSIN_RADIUS; y++) {
	        float a = length(vec2(float(x), float(y))) / float(RSIN_RADIUS);
			if(a > 1.) continue;
	        float w = sinc(a * PI * tx.x) * sinc(a * PI * tx.y);
	        vec2 offset = vec2(float(x), float(y)) * tx;
	        vec4 sample = texture2D_bilinear(texture, (p + offset + vec2(0.5)) / sampleDimension);
	        sum += w * sample;
	        weights += w;
	    }
		
	    return sum / weights;
	}
	
	vec4 texture2D_bicubic( sampler2D texture, vec2 uv ) {
		uv = uv * sampleDimension + 0.5;
		vec2 iuv = floor( uv );
		vec2 fuv = fract( uv );
		uv = iuv + fuv * fuv * (3.0 - 2.0 * fuv);
		uv = (uv - 0.5) / sampleDimension;
		return texture2D_bilinear( texture, uv );
	}
	
	vec4 texture2Dintp( sampler2D texture, vec2 uv ) {
		     if(interpolation == 1)	return texture2D_bilinear( texture, uv );
		else if(interpolation == 2)	return texture2D_bicubic(  texture, uv );
		else if(interpolation == 3)	return texture2D_rsin(     texture, uv );
		return texture2D( texture, uv );
	}

#endregion /////////////// SAMPLING ///////////////

void main() {
    vec2 tx = 1. / dimension;
    vec2 p1 = pos1 * tx;
    
    float dis = distance(v_vTexcoord * dimension, p1 * dimension);
    float inf = 1. - smoothstep(radius - falloff, radius + falloff, dis);
    vec2  stx = v_vTexcoord + (v_vTexcoord - p1) * intensity * inf;
    
    gl_FragColor = texture2Dintp( gm_BaseTexture, stx );
}