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[resolved] Limits for graphics (md3 inside).

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Hi, I'm a novice in game graphics actually... I've been enrolled on an online game in which the programmation is near it's end and I'm the only graphist for the moment. The lead programmer (he's also the team's leader) asked me to begin creating some trees... to export with md3 format. The engine can handle a lot of polygons, but he didn't give me a lot of informations on how much polys I should use for each one. He wont connect since saturday - my first limit (at least the first sample tree must be ready for tests). I just now there'll be forests made from these. I also must export them in .md3, and i have difficulties to find it's limits too (i don't have good sources). I just'd like to know how much tris i should use per tree please (mostly for broadleaf trees) ? Thanks in advance. [Edited by - Valerien on December 25, 2008 10:21:35 AM]

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In the end, a 3d model for a game is just a series of planes to display texture data. You can get by with nice leaf textures. Use as many polygons as you need to define the basic shape/silhouette of the tree and no more.

You should find out more about the scene setup and then adjust the non test models to suit it. If you are rendering out a forest, it's best to have lower quality models to render out distant trees.

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Quote:
Original post by Valerien
I just'd like to know how much tris i should use per tree please (mostly for broadleaf trees) ?

Unfortunately that is impossible to say. It entirely depends on the engine, and variations can be huge depending on how advanced the engine is. In fact, it is not so much about how many polygons an engine can handle. It's about what kind of LOD (level of detail) system it is using.

Without a LOD system, you will very quickly hit the polygon limit with trees. In this case, you should probably try to model very simple trees and mostly play with large alpha blended layers that include branches, twigs and leaves. Maybe something like 500 faces per tree.

With a LOD system, things look already very different. A LOD system will simplify the tree in realtime (or use several pre-defined levels of detail) depending on camera distance, occlusion and other factors. It's hard to give figures here, since so many different ways to design LOD systems exist, and all have very different performance characteristics. With a very simple, geomipmapping-type of appoach (usually the easiest to implement), you can already model a better tree: branches in full 3D, twigs and leaves in small groups of alpha mapped planes. Maybe around 5000 to 10000 faces per tree, assuming the trees are billboarded in the distance by the engine.

With a high-end LOD system, there is essentially no limit. Very high end vegetation rendering systems can handle huge forests full of trees that are made of several hundred thousand faces each. However, it is rather unlikely that your engine has such a LOD engine.

Still, before doing any type of work, you should check with the engine programmer. Trees and vegetation are very specific assets. You are often required to adhere to certain (usually very strict) modeling guidelines, especially if LOD systems are used to post-process the tree afterwards.

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I really thank both of you for your help.

I know the engine is using a LOD system but I'll discuss about it with the programmer.

Thanks again

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If the programmer can't give you a hard maximum on number of vertices/polys, and you don't know what perspective/distance the trees will be viewed from, then just make something that looks good and don't be wasteful (i.e. be efficient with your polygons).

Really, until you see it in game, you don't know how it will look. You can make the nicest tree ever, but if you're only going to be viewing it from a kilometer away, what's the point (you're just wasting precious processing cycles)?

Just use your common sense with what you know about the game unless you can get a hold of the programmer.

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