uniform Params
{
	float start_height;
	float max_height;
	float min_height;
	float step_size;
};

#pragma MSP stage(vertex)
layout(location=0) in vec4 position;
void main()
{
	gl_Position = position;
	out vec3 dir = vec3(position.xy, 1.0);
}

#pragma MSP stage(fragment)
layout(location=0) out vec4 frag_color;
void main()
{
	vec3 ndir = normalize(dir);
	vec3 pos = vec3(0.0, 0.0, start_height);
	float luminance = 0.0;
	float extinction = 0.0;
	while(true)
	{
		if(pos.z<min_height || pos.z>max_height)
			break;

		float density = exp(pos.z/-1000.0);
		luminance += density*exp(-extinction);

		extinction += density*step_size;
		pos += ndir*step_size;
	}

	frag_color = vec4(vec3(luminance), 1.0);
}

/* Expected output: vertex
layout(location=0) in vec4 position;
layout(location=0) out vec3 dir;
void main()
{
	gl_Position = position;
	dir = vec3(position.xy, 1.0);
}
*/

/* Expected output: fragment
layout(binding=80) uniform Params
{
	float start_height;
	float max_height;
	float min_height;
	float step_size;
};
layout(location=0) out vec4 frag_color;
layout(location=0) in vec3 dir;
void main()
{
	vec3 ndir = normalize(dir);
	vec3 pos = vec3(0.0, 0.0, start_height);
	float luminance = 0.0;
	float extinction = 0.0;
	while(true)
	{
		if(pos.z<min_height || pos.z>max_height)
			break;
		float density = exp(pos.z/-1000.0);
		luminance += density*exp(-extinction);
		extinction += density*step_size;
		pos += ndir*step_size;
	}
	frag_color = vec4(vec3(luminance), 1.0);
}
*/