Instancing Polygons in UVW space.

k@rt

Hi All,

This isn't the easiest thing to explain, but I'll try to be as clear as possible.

I recently decompiled a Source model and when looking at the UVW unwrap in 3DsMax I noticed something I havent seen before, and can't figure out how to achieve.

Basically the model contained 3 copied/instanced (i.e. identical) elements each made from (lets say) 50 polygons. Now if I were to make/unwrap this object I would get a total of 150 polys in my UWV space, 50 for each element. I could overlay these on top of each other, but in the end there would still be 150 polys in my UVW space.

However in this model that wasn't the case, each of the 3 identical elements was being textured by the same set of 50 polygons. So if in the viewport you selected a corresponding poly on any of the 3 elements, you would be selecting the same poly in UVW space.

Its like the uvw for each element had been instanced somehow, or to put it more another way; as if the 3 sets of 50 polys have been overlaid one on top of the other and the "glued" or "fused" together, so that only one set of 50 polys remains (which seems to be closer to what is happening)

I can use the break command to separate the polys to get back to the normal 3 sets of 50, but I can't figure out how to do the reverse, i.e. sticking them together in the first place.

I hope this is clear enough, any ideas?

Thanks in advance.

Eric Chadwick

It's not necessary to "instance" the elements, that's likely just a byproduct of using a UV tool like Weld. As long as your UVs are stacked cleanly, they'll export properly to a game format. Maybe Source requires coincident islands to be welded together, but I really really doubt it. A quick way to map UV elements like this, to the identical spots in the UV space, is to first delete all but one of them in the model, then unwrap and UV the remaining one, then collapse the stack and duplicate it around to where it goes.

k@rt

Hi Eric, thanks for the reply. What you say is of course totally correct, and mostly when in that situation I will do as you said, i.e. unwrap and then copy and identical elements. Source doesn't require them to be welded, I just thought that it could be useful to be able to do this sometimes, that way there isnt any risk of de-synching the multiple layers when manipulating the UVWs - which I have done once or twice by accident, and if I have saved and gone past the number of undo levels then that can be a pain.

I realize doing what I am asking isn't essential, I just thought it a handy little technique to employ sometimes, apparaently it's not as "easy" as I'd assumed...

Eric Chadwick

Hmm, I vaguely remember there was a script somewhere that would stack similar shells automatically. In case they got misaligned.

cptSwing

If they're the exact same size, textools can stack them (with it's align tools).. could also help in combination with some vert snapping if they're not completely the same. There's no Max equivalent of Softimage's 'shell matching' script as far as I know, unfortunately.

passerby

ya maya has a script that lets you select a bunch of similar shells and it stacks them all perfect.

FicWill

This likely isn't a step performed by the artist but rather by the model compiler.