Exporting symetric models with Maya

[Kate Laryukov]

Hello,

Im having problems uploading symetric objects. For example, i have create a shoe for the right foot. To create with Maya the left one, i have duplicate the original object and i have set the size to -1 in the correct dimension. In Maya it looks perfect, but when i export it to DAE and i upload both models to SL, both are displayed the same, It is, both are the right shoe.

I am using open collada and Maya 2008. Does anyone know why im having that problem? is it not rigth the way i did the symetry?

Thanks for your help

[WADE1 Jya]

I don't use Maya but this might help (as all software is similar). It sounds like you are maybe doing it wrong. You probably shouldn't use a negative size. Instead use a symmetry modifier which should be one of the tools in Maya.

Modifiers aren't automatically part of a finalized mesh object so you'll need to do a final step of some kind to make the modifier concrete. Sorry I don't know more of the 3D jargon to explain it better, but hope that is of some help.

Likely others will chime in here with more Maya-specific advice of what precisely to do, but if not & you find yourself still somewhat stuck try some google searches about it.

Google is just like an extension of the brain, you don't need to know anything, the knowledge is all floating out there :matte-motes-nerdy:

[Kwakkelde Kwak]

I'm not sure about Maya, but I think the option is called "remove history". That will delete all modifiers and leave you a nice clean mesh (model mesh I mean, not SL mesh). I'm sure Chosen Few can tell you exactly what and how...

[StoneDwarf]

Heya Kate, 

Mirroring a mesh like that only works if you throw a 'freeze transformations' behind it, Modify -> freeze transformations. However, because you used a -1 value with scale, your normals will be reversed. To check this, go to "render" in the view port, switch to 'default quality rendering and turn :two sided lighting" off (by default its on) which can be found in the view port under "lighting" 

After you have followed the steps above, you will have a black mesh. 

Select the mesh in object mode and go to "normals" (polygonal shelf)  then "reverse" That should do the trick and your mesh will be visible in SL as how it is in Maya. 

But, there's one more problem ... The UVs are, if I remember correctly, flipped due to the reversed normals. This can be solved easily by selecting all the UVs (each and everyone that is) and choose, in the UV texture editor panel, "polygons" -> "flip"  

[Chosen Few]

As others have stated, you need to freeze transformations after performing a negative operation, to bring all the values back to positive. Transformations, whether negative or positive, are a localized effect within Maya itself.  They're not a property of the actual geometry, which is why they don't get included in the COLLADA export.  Freezing transformations forces Maya to rebuild the geometry so that its present appearance becomes its actual state.

After a negative operation, the sign flipping from the freeze will end up flipping the normals as well, as Stone pointed out.  So after you freeze the transformations, you'll need to reverse the normals.

To spot things like that as they happen, it's best to work with backface culling enabled, and/or with two-sided lighting disabled.

As for the UV's, they'll remain in the original orientation, which could be good or bad, depending on what you're trying to do.  If you want to flp them, it's easy enough to do in the UV Texture Editor.  Just select all, and then hit Polygons -> Flip -> Options Box, select the axis across which you want to flip, and hit OK.

 

So you know, you should always freeze transformations and delete history before exporting anything.  The presence of either can distort the way data is written and interpreted.

 

Some additional tips, while we're on this subject:

1. Don't use groups.  A group node within Maya is an entity unto itself.  If you negative-scale a group, the geometry inside the group will appear to reverse, but the effect is not real.  The math can get really funky, really quickly, and screw things up royally upon export.

A lot of people are under the mistaken impression that heirarchy in Maya is meant for organizing things for easy selection and such.  That's really not the case. What it's actually for is allowing nodes to control each other, such as the way a shoulder controls and elbow, an elbow controls a wrist, etc., in a skeleton.  For static objects like the kinds of mesh models we make for SL, it's best to steer clear of heirarchy altogether.

If you want to keep your scene organized, use layers.  That's what they're there for.

 

2.  When mirroring a model whose negative side is to be contiguus with the positive side, like if you model half a character's body, and then mirror to create the other half, it's best not to use negative scaling, as this will tend to bork your vertex winding order, among other things.  Not every platform you might export to will care about that (SL probably won't), but some will.  Instead, use the Mesh -> Mirror Geometry function.  This will give you the effect you want, without breaking anything.

[Kate Laryukov]

Thanks all very much,

I followed your steps and it worked perfectly. Thanks for all the explications and advises, I have learnt new things that i didnt know.