//source
//https://www.shadertoy.com/view/ttj3zd

float4x4 matViewProj;
const float4 vecTime;
const float4 vecViewPort;

float lightRangeFactor = 1.0;
float smoothObjectPadding = 0.33;
float lightSaturationFactor = 0.2;
float flickerSpeedFactor = 2;

float iLights;
float4 vecLightPos[8];
float4 vecLightDir[8];
float4 vecLightColor[8];

texture TargetMap;

sampler postTex = sampler_state
{
	texture = <TargetMap>;
	MinFilter = Linear;
	MagFilter = Linear;
	MipFilter = Linear;  
	AddressU = Clamp;
	AddressV = Clamp;
};

float4 FP(float2 fragCoord: VPOS) : COLOR
{
	float2 uv = fragCoord.xy / vecViewPort.xy;
	float3 color = tex2D(postTex, uv).rgb;
	float3 blurColor = float3(0.0, 0.0, 0.0);
	
	float aspectRatio = vecViewPort.x / vecViewPort.y;
	
	float i = 0;
	for(i = 0; i < iLights; i += 1.0)
	{
		// pointlights only
		if(vecLightDir[i].x <= 0 && vecLightDir[i].y <= 0 && vecLightDir[i].z <= 0)
		{
			float4 clipSpacePos = mul(float4(vecLightPos[i].xyz, 1.0f), matViewProj);
			float3 ndcSpacePos = clipSpacePos.xyz / clipSpacePos.w;
			float2 windowSpacePos = float2(((ndcSpacePos.x + 1.0) / 2.0) * vecViewPort.x, ((1.0 - ndcSpacePos.y) / 2.0) * vecViewPort.y);
			
			float2 objectCenter = windowSpacePos.xy / vecViewPort.xy;
			
			float2 v = uv - objectCenter;
			v.x = v.x * aspectRatio;
			float flickerTime = sin(vecTime.w * flickerSpeedFactor);
			
			float min_size = (vecLightPos[i].w * lightRangeFactor / 2.0) / 100;
			float max_size = (vecLightPos[i].w * lightRangeFactor / 2.1) / 100;
			float size = lerp(min_size, max_size, flickerTime);
			
			float smoothSize = size * smoothObjectPadding;
			float circleMix = smoothstep(size, size - smoothSize, length(v));
			
			blurColor.rgb = lerp(blurColor.rgb, color.rgb + (vecLightColor[i].xyz * lightSaturationFactor), circleMix);
		}
	}
	
	float4 fragColor = float4(blurColor, 1.0);
	return fragColor;
}

technique
{
	pass one
	{
		PixelShader = compile ps_3_0 FP();
	}
}