I have this project , displaying virtual forest . Displaying a lot of trees , eats a lot of resources, cause a lot of polygons is displayed at the same time , i need to use LOD , but i am green in that kind a matter.Could you direct me , or tell me where can i find algorithms or sources , which uses LOD on 3d models ... I dont give me LOD about landscape , this isnt what i need. LOD of 3d models , that''s what i need. Thanks

Take a look in the articles section on here and on gamasutra. It''ll tell you what to look for - subdivision surfaces, I think, is one of the ways.

You might want to search the forums for impostors.

Basically, it''s a technique where you render the mesh (in this case the tree) to a texture, and then just render the texture. It saves rendering alot of polygons.

WEll one cheap and easy way(but it could cause some model poping if done wrong) is to use LOD models.
Basicly you have the same tree but in different resolutions.

Perhaps one tree with ultra hugh poly count for when you stand just next to it.
one tree with a normal polycount for distances of up to about 50 meters.
One with a low polycount(perhaps 5 segments in the radius of the stem) for distances up to 200 meters
an ultra low model with perhaps 6 polygons in total(4 for thestem and 2 for the branches, it depends on the tree) for up to 1 km
and lastly for the rest you can use a billboard that only rotate on the y axis) with the tree as a texture

Just render the different tree models acording to the distance to the camera

[edited by - lc_overlord on December 1, 2003 5:12:33 PM]

Thanks for your answers ,
James Trotter you''re suggesting me to render meshes into a texture , but how can i do that in my program ??? Of course i could render a model in 3dmax , and then put the picture of a tree on a billboard , but that''s too primitive, but good idea.

lc_overlord , i like your answer ,but the same question , can i lower the number of polygons in my program ,if so , what algorithm should i use . Or that was idea to do this outside a program ,and have 3 models.I know this is kind a hard ...

Thanks again

while it is possible to do this in runtime, it would take way to much processing power.
The processitself is simple, you simply take the two vertics that are closest to eachother and merge them together, repeat this until it reaches the desired polycount.

However if you make tree diferent resolution models(made by you in your 3d modeling program) models of the tree you would not just save in on cpu/gpu cycles but you could make the tree''s look better than the automatic method.