billboarding in Frustum


I want to render billboarded polygons that do not change their size as z-depth changes. I know how to do billboarding and that is not the problem.

I tried transforming my vertices by the inverse of the projection matrix. I figure

inverse§ * vertex = vertex’

P * M * vertex’ = clip_coordinates

but that gives some weird results (of course!).

Anyone see an easy solution to this?


How about just drawing them in orthogonal projection, instead of perspective as you try to do?

Of course, you’d have to figure out the 2d position of the 3d center of each billboard first, by yourself, but then just pop into ortho-mode and draw away.

I will have to try that one more time, since I think I had a bug before.

Other suggestions are still welcomed.