geom.cpp

#include "geom.h"
#include <Windows.h>

bool WorldToScreen(vec3 pos, vec3& screen, float matrix[16], int windowWidth, int windowHeight) {
	Vec4 clipCoords;

	clipCoords.x = pos.x * matrix[0] + pos.y * matrix[4] + pos.z * matrix[8] + matrix[12];
	clipCoords.y = pos.x * matrix[1] + pos.y * matrix[5] + pos.z * matrix[9] + matrix[13];
	clipCoords.z = pos.x * matrix[2] + pos.y * matrix[6] + pos.z * matrix[10] + matrix[14];
	clipCoords.w = pos.x * matrix[3] + pos.y * matrix[7] + pos.z * matrix[11] + matrix[15];

	if (clipCoords.w < 0.1f)
	{
		return false;
	}

	vec3 NDC;

	NDC.x = clipCoords.x / clipCoords.w;
	NDC.y = clipCoords.y / clipCoords.w;
	NDC.z = clipCoords.z / clipCoords.w;

	screen.x = (windowWidth / 2 * NDC.x) + (NDC.x + windowWidth / 2);
	screen.y = -(windowHeight / 2 * NDC.y) + (NDC.y + windowHeight / 2);

	return true;
}