I am stuck with this problem at the moment.
I’m trying to order my vertixes so that OpenGL can do backface culling
for me, I can’t specify my points in order manually because my code
just doesn’t work like that. The points need to be reordered
For example, my GLCuboidObj can accept just two points, a width float
and height float. It builds all the GLQuad3dObj 's with their vertexes
all in the right place. But what it can’t know YET, is how to order the
vertexes for backface culling. This is what I’m completely stuck on.
What I want is to reorder my polygons to be drawn in the clockwise
order (or reverse, I forget which but its not important right now as
its simple to change) when they have their front face viewed. I don’t
actually have them drawn in that order at the moment, and I need to
adapt the code so that I can take 2 triangles, and let the code reorder
the points of both of them so that they are both drawn as opposite
sides of an object. I thought I could do it with dot product, but
unfortunately dot product never returns an angle bigger than 180, so I
can’t tell which direction two vectors starting from the origin are
winded at. Unless perhaps you know of a way to find the winding angle
even if its bigger than 180? Screen coordinates don’t come into this of
course. Manual culling I’ll leave to OpenGL.
Thanks for your time