PostProcess.450core.vert

// GLSL post-processor vertex shader

#version 450 core

layout(location = 0) out vec2 vTexCoord;

out gl_PerVertex
{
	vec4 gl_Position;
};

/*
This function generates the coordinates for a fullscreen triangle with its vertex IDs:

(-1,+3)
   *
   | \
   |   \
   |     \
   |       \
(-1,+1)    (+1,+1)
   *----------*\
   |          |  \
   |  screen  |    \
   |          |      \
   *----------*--------*
(-1,-1)    (+1,-1)  (+3,-1)
*/
vec4 GetFullscreenTriangleVertex(int id)
{
	return vec4(
		(id == 2 ? 3.0 : -1.0),
		(id == 0 ? 3.0 : -1.0),
		1.0,
		1.0
	);
}

void main()
{
	// Generate coorindate for fullscreen triangle
	gl_Position = GetFullscreenTriangleVertex(gl_VertexIndex);
	
	// Get texture-coordinate from vertex position
	// -> Don't flip U-tex-coord here (like in HLSL), due to different coordinate system
	vTexCoord = gl_Position.xy * vec2(0.5, -0.5) + 0.5;
}