typedef struct
{
	float x, y, z, thx, thy, thz;
} Camera;

typedef struct
{
	float x, y;
	int beyond;
} Point2D;

typedef struct
{
	float x, y, z;
} Point3D;

void TransformPoint3DToPoint2D(Point3D *p3D, Camera *C, Point2D *p2D)
{
	float x, y, z, cx, cy, cz, sx, sy, sz, dx, dy, dz, ex, ey, ez, a;

	if ((p3D == NULL) || (C == NULL) || (p2D == NULL))
	{
		return;
	}

	a = 90.0;
	x = p3D->x - c->x;
	y = p3D->y - c->y;
	z = p3D->z - c->z;
	ex = 0.0;
	ey = 0.0;
	ez = cos(a / 2) / sin(a / 2);
	cx = cos(C->thx);
	cy = cos(C->thy);
	cz = cos(C->thz);
	sx = sin(C->thx);
	sy = sin(C->thy);
	sz = sin(C->thz);

	dx = cy * (sz * y + cz * x) - sy * z;
	dy = sx * (cy * z + sy * (sz * y + cz * x)) + cx * (cz * y - sz * x);
	dz = cx * (cy * z + sy * (sz * y + cz * x)) - sx * (cz * y - sz * x);

	p2D->x = ((ez / dz) * dx) + ex;
	p2D->y = ((ez / dz) * dy) + ey;
	p2D->beyond = dz < 0.0;
}