Skin issue

#1

I’m having a weird issue with the Skin modifier and I’m really hoping someone out there knows how to fix it.

I’m using 3ds Max 2012, but it’s an issue that has occasionally popped up for me since Max 2009. When I send a scene to render, there will be random frames where a bunch of verts will shoot back to the bind pose, then snap back into place a few frames later. I could go through the animation frame by frame and it wont happen in the viewport, but if I render the sequence out or make an animation preview, it’ll happen. After that I can scan through the timeline and see it happening. What frames it happens to seems to be random and unique each time I encounter it. I could render the sequence ten times and it would occur in a different part of the animation each time.

There’s nothing fancy going on in the modifier stack. It goes;

TurboSmooth
Skin
Morpher
Editable Poly

I’m pretty sure I tracked it down to the turbosmooth, but I’m not sure. If i delete it from the stack the verts snap back into place, so I just add a new turbosmooth and re-render the broken frames. But there’s gotta be a permanent solution.

Here’s what it looks like…

Thanks,
Zac.

#2

wow never had this kind of problems before… Have you tried using meshsmooth instead ?

#3

Bake them in skin modifier.

#4

I haven’t tried the MeshSmooth on this model yet, but I tried that last time this issue came up and it didn’t fix it.

And I’m not sure what you mean by “bake them in skin modifier”, do you mean to bake it down to a vertex animation? Either way, I think the verts that are acting up are ones added in from the TurboSmooth, so they come in after the skin modifier. It might do a better job smoothing it if it were baked down like that, but I could only do it when the animation was 100% done, which is a little inconvenient.

The only thing i can reason is that when the TurboSmooth is added to the stack, some of the new verts “forget” their skin weights, but I don’t understand why, or what it is about my setup that causes this to continually happen to me. I even caught it happening to the headlights, and that doesn’t even have a skin on it, just a global FFD.

#5

I have had this happen numerous times with Turbosmooth, and almost without fail switching to meshsmooth did the trick. If It does not fix the problem off the bat, you may want to try the different smoothing algorithms in MeshSmooth. This will run much slower however, so you may want to use the MS instead of the TS for render, but use the TS for view-port, or no smoothing at all.

If that doesn’t work caching out the Geo sounds like a good Idea. Going with the Point cache modifier (the local one not the WSM ( assuming that your mesh is parented to the rig)) You can use it for whenever you aren’t animating, and just turn it off when you do. Then after your animation is done, just re-cache the geo. Takes just a second.

Any other causes could be because of a topology changing modifier under your skin, like an edit poly, or smoothing, or whatever that is messing up your vert order.

#6

I do have an edit poly in the stack, but it’s above the skin, just under the TurboSmooth. When I collapsed the symmetry down I didn’t notice two vertexes that didn’t connect, I didn’t catch it until after I made all of my morph targets though so I just welded it in the edit poly. But would that reorder the two vertexes I welded or would it affect the mesh as a whole?

Either way I’ll throw the MeshSmooth on there and see if that corrects it.

#7

I Have had the vert problem that you are referring to from using a symmetry as well. To copy your skin weights off of that mesh and onto a clean one you can do this simple trick.

[ul]
[li]Duplicate your mesh
[/li][li]delete any modifiers on that duplicated mesh
[/li][li]fix your topology
[/li][li]skin wrap to original mesh (use face mode and weight all points)
[/li][li]convert your skinwrap to a skin modifier
[/li][li]replace any other modifiers, turbosmooth etc
[/li][li]delete your original mesh
[/li][/ul]

#8

Yeah, I’m not as much worried about the skin weights as I am all the morph targets I created for it. Worse case I’ll just delete that edit poly, the separation is inside the mouth so I doubt it’ll ever be a problem.

Thanks for the help.

#9

You can use a similar skin wrap trick to rebuild your morph targets after changing the topology as well, if it was an issue. But if it is in the mouth, no biggie. :slight_smile:

#10

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