#include "../shaderenv.h"

struct fragment
{
	float2 texCoords:  TEXCOORD0; 
};


inline float2 ComputeTexCoords(float2 tex, float2 v, float dist, float scale, float distScale)
{
	const float2 center = float2(.5f, .5f);
	const float2 newPos = -v * dist * distScale;
	//const float2 newPos = v * dist * distScale;

	//return (tex - center - newPos) / scale + newPos + center;
	return (tex - center) / scale + center + newPos / scale;
	//return tex / scale - center;// + center + newPos;
}


inline float4 ComputeColor(sampler2D tex, float2 texCoords, float2 v, float dist, float scale, float distScale)
{
	const float2 newTexCoords = ComputeTexCoords(texCoords, v, dist, scale, distScale);
	return tex2Dlod(tex, float4(newTexCoords, 0, 0));
}


float4 LenseFlare(fragment IN, 
				  uniform sampler2D colorsTex,
				  uniform sampler2D flareTex1,
				  uniform sampler2D flareTex2,
				  uniform sampler2D flareTex3,
				  uniform sampler2D flareTex4,
				  uniform sampler2D flareTex5,
				  uniform float2 vectorToLight, // vector to current light position
				  uniform float distanceToLight, // distance to current light position
				  uniform float sunVisiblePixels
				  ): COLOR
{
	// center color
	const float4 color = tex2Dlod(colorsTex, float4(IN.texCoords, 0, 0));
	
	const float scale = 0.3f;

	float4 flare[8];

	flare[0] = ComputeColor(flareTex1, IN.texCoords, vectorToLight, distanceToLight, 1.0f * scale, 1.0f);
	flare[1] = ComputeColor(flareTex2, IN.texCoords, vectorToLight, distanceToLight, 0.7f * scale, 1.0f / 3.0f);
	flare[2] = ComputeColor(flareTex3, IN.texCoords, vectorToLight, distanceToLight, 0.25f * scale, 0.7f);
	flare[3] = ComputeColor(flareTex4, IN.texCoords, vectorToLight, distanceToLight, .7f * scale, -1.0f / 2.0f);
	flare[4] = ComputeColor(flareTex3, IN.texCoords, vectorToLight, distanceToLight, .4f * scale, -1.0f / 6.0f);

	flare[5] = ComputeColor(flareTex5, IN.texCoords, vectorToLight, distanceToLight, .1f * scale, 0.5f);
	flare[6] = ComputeColor(flareTex5, IN.texCoords, vectorToLight, distanceToLight, .2f * scale, -0.25f);

	flare[7] = ComputeColor(flareTex2, IN.texCoords, vectorToLight, distanceToLight, 1.0f * scale, -1.0f);

	float4 result = color;

	//result.xyz = float3(0);
	sunVisiblePixels = clamp(sunVisiblePixels, .0f, 100.0f) * 0.01f;

	for (int i = 0; i < 8; ++ i)
		result.xyz += flare[i].xyz * sunVisiblePixels;

	return result;
}