gzdoom/wadsrc/static/shaders/glsl/main.vp

in vec4 aPosition;
in vec2 aTexCoord;
in vec4 aColor;
#ifndef SIMPLE	// we do not need these for simple shaders
in vec4 aVertex2;
out vec4 pixelpos;
out vec2 glowdist;
#endif

out vec4 vTexCoord;
out vec4 vColor;

void main()
{
	#ifndef SIMPLE
		vec4 worldcoord = ModelMatrix * mix(aPosition, aVertex2, uInterpolationFactor);
	#else
		vec4 worldcoord = ModelMatrix * aPosition;
	#endif

	vec4 eyeCoordPos = ViewMatrix * worldcoord;

	vColor = aColor;

	#ifndef SIMPLE
		pixelpos.xyz = worldcoord.xyz;
		pixelpos.w = -eyeCoordPos.z/eyeCoordPos.w;

		glowdist.x = -((uGlowTopPlane.w + uGlowTopPlane.x * worldcoord.x + uGlowTopPlane.y * worldcoord.z) * uGlowTopPlane.z) - worldcoord.y;
		glowdist.y = worldcoord.y + ((uGlowBottomPlane.w + uGlowBottomPlane.x * worldcoord.x + uGlowBottomPlane.y * worldcoord.z) * uGlowBottomPlane.z);
	#endif
	
	#ifdef SPHEREMAP
		vec3 u = normalize(eyeCoordPos.xyz);
		vec4 n = normalize(TextureMatrix * vec4(aTexCoord.x, 0.0, aTexCoord.y, 0.0));	// use texture matrix and coordinates for our normal. Since this is only used on walls, the normal's y coordinate is always 0.
		vec3 r = reflect(u, n.xyz);
		float m = 2.0 * sqrt( r.x*r.x + r.y*r.y + (r.z+1.0)*(r.z+1.0) );
		vec2 sst = vec2(r.x/m + 0.5,  r.y/m + 0.5);
		vTexCoord.xy = sst;
	#else
		vTexCoord = TextureMatrix * vec4(aTexCoord, 0.0, 1.0);
	#endif
	
	gl_Position = ProjectionMatrix * eyeCoordPos;
	
	// clip planes used for reflective flats
	gl_ClipDistance[0] = worldcoord.y - uClipHeightBottom;
	gl_ClipDistance[1] = uClipHeightTop - worldcoord.y;
	
	gl_ClipDistance[2] = worldcoord.y - uClipSplit.x;
	gl_ClipDistance[3] = uClipSplit.y - worldcoord.y;
}