CGI/exercise2/glsl/sky.vert

#version 330
// This source code is property of the Computer Graphics and Visualization 
// chair of the TU Dresden. Do not distribute! 
// Copyright (C) CGV TU Dresden - All Rights Reserved

uniform mat4 mvp;

out vec4 clipPos;

void main()
{
    clipPos = vec4(		float((gl_VertexID << 1) & 2) - 1.0,
                        float((gl_VertexID +  1) & 2) - 1.0,
                        float( gl_VertexID       & 2) - 1.0,
                        1.0);

	gl_Position = mvp * clipPos;
	gl_Position.z = 0.5 * gl_Position.w;
}