tank treads

Josh Winn

I am getting used to modeling in XSI and am working on a tank that would be suitable for games currently in development (360, PS3, PC). What I am unsure about is how the treads are animated! Is the actual geometry turning around, perhaps with coded physics, or is it merely animated textures, some animation with the sag at the top? I'd like there be enough loops in there to accommodate whatever is being done to move these things around.

I couldn't find any tank screens from some of the new WWII games, Brothers In Arms: Hell's Highway, Medal of Honor: Airborne, or Red Orchestra: Ostfront 41-45. I would imagine the teeth (A in image) are moving somehow.

I'd like to get the cylinder pieces (B in image) into the model, as it is a noticeable part of the silhouette, but it seems still to be a waste of polys (single or perpendicular planes maybe? 3-sided would be pushing it?), games are still using the bleh-box-with-a-texture-treads...

Who can guess what tank I'm doing from the cropped reference?

EarthQuake

one of the biggest reasons for doing treads like the COD pic is that you can simply just offset tiled uvs to make it look like its moving, if you model each link you're talking about one pain in the ass rig, not really suitable for realtime work.

CrazyButcher

animated UVS as EQ said,
the best you could do is stick out 2 quads along the side (one for top, one for bottom, due to lighting issues you need 2), and then put an alphatested texture on it, animated just like the treads themselves.

Vailias

there are 2 ways I've seen tank treads work.

1 is texture animation (unreal tournament and almost every game out there) 2 is moving the treads just enough to loop properly, usually the length of one major link to the next. Tribes vengeance did this with their jumptank. it had these protrusions from the main tread that were actual geo. They animated those so that one protrusion moved to line up where the previous one was, when looped it was seamless.

CrazyButcher

game I worked on, did it the same way (aniamte 1 move), however if you want deforming tracks (as the wheels go up and down), you are doomed with that kind of geometry animation, I think.

Josh Winn

Ah ok, guess I'll create it with the animated UVs in mind. Thanks for the information.

[ QUOTE ]
animated UVS as EQ said,
the best you could do is stick out 2 quads along the side (one for top, one for bottom, due to lighting issues you need 2), and then put an alphatested texture on it, animated just like the treads themselves.

[/ QUOTE ]

Which side/top/bottom you are referring to? Using a transparent plane going around the tread for the (B) parts of the links? I'm not sure what you mean by using 2, unless you meaning putting another perpendicular to fake volume from both side and above views

CrazyButcher

I mean bottom and up, because two-sided lighting of polygons isnt that common.

oooo
WHEELS

TOP
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BOTTOM

you would still have a side polygon for the main tracks, but for the part B I guess you dont need that, as they are too small