uniform sampler2D ReductionTexture;
uniform vec2 TexelSize;
uniform int Iteration;
uniform int Mode; // 0 == initalize, 1 == reduce

smooth VSData vec2 TexPos;

uniform mat4 Orthographic;

#ifdef VERTEX_SHADER
in vec2 Vertex;

void main()
{
	vec4 result = Orthographic * vec4(Vertex, 0, 1);
	gl_Position = result;
	TexPos = Vertex;
}


#elif defined FRAGMENT_SHADER
out vec4 FsColor;

void main()
{
	ivec2 frag = ivec2(TexPos);
	if(Mode == 0)
	{
		FsColor = texelFetch(ReductionTexture, frag, 0);
		return;
	}

	frag *= 2;
	vec4 max = texelFetch(ReductionTexture, frag, 0);
	vec4 test = texelFetch(ReductionTexture, frag + ivec2(0, 1), 0);
	if(test.r > max.r)
		max = test;
	test = texelFetch(ReductionTexture, frag + ivec2(1, 0), 0);
	if(test.r > max.r)
		max = test;
	test = texelFetch(ReductionTexture, frag + ivec2(1, 1), 0);
	if(test.r > max.r)
		max = test;

	FsColor = max;

}

#endif