The static objects and elements, whether in game or animation, generally have the same requirements. Static objects and elements have immobile surfaces, which means that the vertexes never move relative to each other. This allows for a little greater freedom as far as the use of triangles is concerned, but only in final models, with texture coordinates and materials set up properly.
This means that if any 3D sculpting is intended, the base model should first appear in quad topology before being sculpted, and then optimized with the hi-resolution geometry and textures handy.
N-Gons are only allowed if no sculpting is intended, but otherwise are oque to use.
Triangles may somewhat help to keep the polycount down to the minimum. They are alos good for times when you need some sort of sharp "lip" on a rigid shape. However, keep in mind that triangles can only be used in such static areas where you are sure that the vertexes defining the triangle will not move with respect to each other during the animation.
There are engines that support the use of holes in static geometry, like CryENGINE 2 by CryTek, but get around the hole-collision issue by placing proxy geometry around items. Proxy objects are usually generated by copying the mesh and either manually or automatically reducing it's polycount to somewhere below 500-1000 triangles. The proxy may use all trianles if desired, since the actual mesh doesn't ever get rendered.
Dense / High Polycount Areas
The use of high polycount in static geometry for animation or gaming is highly undesired. It is generally recomended to keep the polycount as low as possible, for conservation of time during frame rendering or improvement of real-time 3D performance, depending on the task. This is the primary reason for allowing the use of triangles in static geometry.
Vertexes that are surrounded by (define one end of) five edges are allright to use in static meshes, but watch out for those if you will 3D-scult your high-resolution model in ZBrush or mudbox. They are absolutely fine on the low-resolution geometry that will be used in the actual 3D game engine or during frame rendering, so worry about these only before the high-resolution model is sculpted.
These are alos fine, but the same considerations apply as for 5-edged vertexes.
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