anyone have any idea how many billboard trees you can put on a track. i'm trying a convert of a well known track and delete all the old fake trees and have started to use the trees from the joesville section with some scaling to make them look somewhat realistic. i think to cover the track i'll probably end up with something like 2000-300 trees, is that to many?
The only limiting factors are the same as for any other object: tricount and material-related properties (alpha blending/chroma, shader complexity, texture size, ...). By my knowledge, billboarding doesn't impose any new limitations. Worth advising is that you could use a random poly selection script on the object to select xx% of the polys, detach them to a new object and set up the VisGroups (A-D) so they will be loaded based on the user's track detail level setting. For example, Low detail level would only show 10% of the trees, Medium would add 20% to the original 10%, High adds another 30% to the 10% + 20%, and Max would also display the remaining 40%.
At the moment (mostly for testing purposes), I have a 'forest' of about 18,000 trees (36,000 triangles), one object, all of which use the same material, all as "billboards". I don't really know how much help that information is to you by itself. I have a modest graphics card (nVidia GTX465), and I haven't even started optimization at all yet ( like splitting up the 36,000 triangle mesh! ), but I'm still getting very usable framerates when testing. I believe my entire scene is well over 1 million triangles (maybe more like 1.6), and I only have about 70 or 80 or so materials (at the moment). I think you'll be ok with 2000-3000 trees I think the overhead for billboarding is not much more than just drawing the polys--if I had to guess, the billboarding is probably all done within the vertex shader (i.e. on the GPU, very fast!).
