Reversing order of triangles during a strip


This is driving me crazy… the seems to be nothng on google, redbook, msdn, etc anywhere, just hints at to whats possible in realtime rendering…

I have a strip that I want to…bend halfway through the ordering. I read in real time rendering that if you list the vertex twice the face ordering will swap, sort of allowing you to turn corners with the strip.

I’m attempting to do something like this:

A simple grid:


My strip is formed like this:


However in my application after I use each ‘swap’ vertex the facing seems to swap backwards as well.

Anyone know the proper way of doing this?

Many thanks


With your numbering of the grid vertices try: 0314255584736

The triangles generated by this scheme and their winding are:
031 CCW
314 CW
142 CCW
425 CW
255 CCW (null triangle)
555 CW (null triangle)
558 CCW (null triangle)
584 CW
847 CCW
473 CW
736 CCW

You see that the winding keeps alternating correctly. In your version triangle 584 was in a CCW position in the strip, but it’s CW in reality.
If you want to take the next corner the strip would continue with 6697… and so on.

[This message has been edited by Relic (edited 02-16-2001).]

Champion… I spent 2-3 hours last night looking for more information on that subject.

It’s now working perfectly.

Many thanks


Good ol’ plain paper and pencil work.