Optimizeinplace broke completely my mesh if I call it a second time even if this vidmem object is restored before with the original VB and IB that was used the first time. So what does Optimizeinplace appart changing IB& VB This happen only if I change the subset attribute as long as I don't give another subset number all is well. this serve for terrain purpose What I try to do is updating this mesh with heightmap when time come (changing location). Load time: 1-Loading a mesh in sysmem that contain a flat grid 1-Saving its original IB&VB and creating the vidmem mesh that is a copy of the original. (flat grid) Each update: 1-Update of the original VB.p.y with heightmap value 2-Update the mesh in vidmem with those IB&VB (IB is to restore) 3-Locking attribute of the vidmem mesh given various number to sort by texture (two for now) 4-Call optimiseinplace with ATTSORT (otherwise it run at...0.75fps) First update all is well the second time all my poly seem to become crasy displaying all over the scene. This problem have something to do with the attribute cause as I said if I give the same subset number to all the poly all work well. but the doc doesn't say anything usefull about those things. Thanks for any Help I tried to do it all manually but indexed STRIP are a pain and LIST run 15 fps less than using the mesh method above. Dan Edited by - dansteph on January 11, 2002 9:50:42 AM

Resolved.

for record, Don''t keep the IB and VB pointer appart just do:

Mesch->LockIndexBuffer()

That''s it

Dan