Fastest way of converting a quad to a triangle strip?
- by Tina Brooks
What is the fastest way of converting a quadrilateral (made up of foyr x,y points) to a triangle strip? I'm well aware of the general triangulation algorithms that exist, but I need a short, well optimized algorithm that deals with quadrilaterals only.
My current algorithm does this, which works for most quads but still gets the points mixed up for some:
#define fp(f) bounds.p##f
/* Sort four points in ascending order by their Y values */
point_sort4_y(&fp(1), &fp(2), &fp(3), &fp(4));
/* Bottom two */
if (fminf(-fp(1).x, -fp(2).x) == -fp(2).x)
{
out_quad.p1 = fp(2);
out_quad.p2 = fp(1);
}
else
{
out_quad.p1 = fp(1);
out_quad.p2 = fp(2);
}
/* Top two */
if (fminf(-fp(3).x, -fp(4).x) == -fp(3).x)
{
out_quad.p3 = fp(3);
out_quad.p4 = fp(4);
}
else
{
out_quad.p3 = fp(4);
out_quad.p4 = fp(3);
}
