Hey, I''ve been doing some work on edge cutting trying to decrease the LOD of a model as it gets further away. I haven''t really tried anything in code so i''m wondering, how would i best write a piece of code that cuts edges to vertices for all of the model? Michael Nolan

If I''m interpreting the question correctly (edge cutting==edge collapse), there''s been a LOT of research into this area.

One of the most popular techniques (even made its way into a D3DX function) is Progressive Meshes. Hugues Hoppe has done a lot of work in this area on both the error metric side and the practicalities side:

http://research.microsoft.com/~hoppe/

VIPM (View Independent Progressive Meshes) tend to be the most suitable for realtime.

The classical VIPM methods create a new vertex position when an edge is collapsed (e.g. the centre of the two vertices on the edge in such a way that volume is preserved to some extent).

A visually acceptable adaptation which is particularly suited to realtime use is to snap to one of the vertices instead.

AFAIK Jan Svararovsky (ex MuckyFoot) was &#111;ne of the first to propose this idea. It''s been expanded into a more generic "sliding window" technique by various people during a discussion &#111;n GD-Algorithms, most noticably Tom Forsyth (Mucky Foot) and Charles Bloom (Oddworld). Some interesting discussions regarding sliding window VIPM and other PM topics arising from various discussions are &#111;n www.cbloom.com. I think you''ll also find some presentations by Tom and separately by Jan in archives of Meltdown and GDC slides.<br><br>The advantage of "snapping" to the least costly vertex when you collapse and sliding window (incl. sort indices and vertices of mesh into reverse collapse order) is you can get visually decent LOD without needing to change ANY vertices in the VB - and even without needing to change indices.<br><br> <br><br>–<br>Simon O''Connor<br>Creative Asylum Ltd<br><A HREF="http://www.creative-asylum.com">www.creative-asylum.com</A>