module maths.Perspective;

private {
	import maths.Vec;
	import maths.Matrix;
}



vec4 perspDivAndViewport(vec4 ppos, vec2i screen) {
	ppos.x /= ppos.w;
	ppos.y /= ppos.w;
	ppos.z /= ppos.w;
	
	ppos.x += 1f;
	ppos.x *= .5f;

	ppos.y += 1f;
	ppos.y *= .5f;

	ppos.z += 1f;
	ppos.z *= .5f;
	
	ppos.x *= screen.x;
	ppos.y *= screen.y;
	
	ppos.w = 1.f / ppos.w;
	
	return ppos;
}



vec3 unproject(vec3 spos, mat4 perspM, vec2i screen) {
	perspM = perspM.inverse;
	
	spos.x /= screen.x;
	spos.y /= screen.y;
	spos *= 2.f;
	spos -= vec3(1.f, 1.f, 1.f);
	spos.y *= -1;
	
	vec4 tmp = perspM.xform(vec4(spos.x, spos.y, spos.z, 1));
	return vec3(tmp.x * tmp.w, tmp.y * tmp.w, tmp.z * tmp.w);
}