#version 450
layout(set = 0, binding = 0, std140) uniform UBO
{
   mat4 MVP;
   vec4 SourceSize; // Not used here, but doesn't hurt
};

float color_blend(float color_prev, float color_curr, float x)
{
   float sum = color_curr;
   sum = sum + color_prev;
   return sum / 2.0;
}

#pragma name Composite blending

#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;
void main()
{
   gl_Position = MVP * Position;
   vTexCoord = TexCoord;
}


#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;

void main()
{
   vec2 onePixel = vec2(1.0, 1.0) / SourceSize.xy;
   vec3 currentColor = texture(Source, vTexCoord).rgb;
   vec3 prevColor = texture(Source, vTexCoord - vec2(onePixel.x, 0)).rgb;

   float r = color_blend(prevColor.r, currentColor.r, vTexCoord.x);
   float g = color_blend(prevColor.g, currentColor.g, vTexCoord.x);
   float b = color_blend(prevColor.b, currentColor.b, vTexCoord.x);
   FragColor = vec4(r, g, b, 1.0);
}