//This shader file is part of FLAR - Advanced Renderer for Freelancer by Schmackbolzen
//If you use the supplied shader files you may not modify them unless you state in them what you changed
//and also mention the source or who the author is.
//
//PBR bloom upsample shader for FLAR by Schmackbolzen based on code from https://learnopengl.com/Guest-Articles/2022/Phys.-Based-Bloom
//The only bug fix is using different filter radii for each direction since the texture is not square

#version 330
uniform sampler2D srcTexture;
uniform float filterRadiusX;
uniform float filterRadiusY;

in vec2 texCoord;
layout (location = 0) out vec3 upsample;

void main()
{	
	float x = filterRadiusX;
	float y = filterRadiusY;

	// Take 9 samples around current texel:
	// a - b - c
	// d - e - f
	// g - h - i
	// === ('e' is the current texel) ===
	vec3 a = texture(srcTexture, vec2(texCoord.x - x, texCoord.y + y)).rgb;
	vec3 b = texture(srcTexture, vec2(texCoord.x,     texCoord.y + y)).rgb;
	vec3 c = texture(srcTexture, vec2(texCoord.x + x, texCoord.y + y)).rgb;

	vec3 d = texture(srcTexture, vec2(texCoord.x - x, texCoord.y)).rgb;
	vec3 e = texture(srcTexture, vec2(texCoord.x,     texCoord.y)).rgb;
	vec3 f = texture(srcTexture, vec2(texCoord.x + x, texCoord.y)).rgb;

	vec3 g = texture(srcTexture, vec2(texCoord.x - x, texCoord.y - y)).rgb;
	vec3 h = texture(srcTexture, vec2(texCoord.x,     texCoord.y - y)).rgb;
	vec3 i = texture(srcTexture, vec2(texCoord.x + x, texCoord.y - y)).rgb;

	// Apply weighted distribution, by using a 3x3 tent filter:
	//  1   | 1 2 1 |
	// -- * | 2 4 2 |
	// 16   | 1 2 1 |
	upsample = e*4.0;
	upsample += (b+d+f+h)*2.0;
	upsample += (a+c+g+i);
	upsample *= 1.0 / 16.0;
}