Maya Blendshapes & Tricky Target Mesh

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Old 02 February 2013   #1
Maya Blendshapes & Tricky Target Mesh

I'm creating facial blendshapes for my character to be rigged. I duplicated the body, chopped off the head, and used that mesh to create facial expressions. Problem is, I didn't realize that by deleting the body faces, it doesn't deform correctly (freaks out) when I attach it to target mesh.

Now the only two options I can think of is separating the head from the body, and somehow finding a way to blend the shaders together, or doing all the blendshapes over again (ouch).

My question is there a way to get the heads to work properly with the target mesh? Is maya going to be stubborn and not recognize that some faces might be deleted, but the heads are otherwise the same as original? I want to keep the body one piece.
Old 02 February 2013   #2
What you'll need to do is chop the head off your full body mesh again, keeping both pieces, ie. the head and body. You have to do it in one operation and the head bit has to be exactly the same faces as your heads that you did all the blendShapes on.

Then you have to combine those 2 pieces again, making sure you select the head piece first. Then select and merge the pairs of border verts along the head/body seam. And delete history.

So now you are kind of back where you started, with a full body mesh, except you have changed the vertex order so that the vert indexes of the head portion of the full body mesh now match the vert indexes of your separated heads.

Now you can create a blendshape on the full body and add all your separate head targets. Do this with the "check topology" option unchecked when you create the blendshape and things should work correctly.

As confusing as this whole process may sound, it is pretty standard workflow for what you are trying to achieve. Its worth getting it.

Old 02 February 2013   #3
Thank you for the reply, but it seems this did not work as well. I extracted the head from the body, then combined them as per your instructions. The target head still deforms strangely.

I suppose I have to face the facts to do the blendshapes over again. :/
Old 02 February 2013   #4
The process should work. But I guess things can go wrong. Do you have good uv's on these models? If so you can use the mesh|"transfer attrs' tool to morph the neutral mesh into your existing shapes, to save some time. ie transfer vertex positions only, and use uv sample space. While history is live, you can even pain weights on the transferAttrs node. Remember to delete history after though.

Old 02 February 2013   #5
The UVs are solid. I'm having a bit of difficulty imagining what you are describing. Is this done in the texture editor? I can imagine using the blendshape meshes as "go live" and matching the vertices there, which is what I'm doing to re-do the blendshapes. Is there a screencapture I can see to know what you are talking about?
Old 02 February 2013   #6
Might be simpler to just use the cut off head as a wrap deformer. You could avoid all the point order issues like that.
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Old 02 February 2013   #7
@lyzarts: Open the docs, goto the serach tab, enter "mesh transfer attributes", its the result at the top of the list. This tool pretty much does what you are doing now, except its a one click affair. It uses the uvs as a way of mathcing the verts between two different meshes. Then it moves the verts from one mesh to the position of the other. In your case with matching verts and uvs, it would be doing a point to point snap. But it also works on meshes that have different topologies.

@kyleb2112: While this might be the simplest one to set up, it is by far the worst performance wise. Even in exclusive bind mode a wrap is way slower than a blendshape. I guess it depends on what you need.

@lyzarts: Im not sure why you are having such trouble with my first suggestion. You said you have a series of head shapes. Presumably you also kept a neutral shape. I'd also assume that if you added those targets to the neutral head it would work fine, right? Ok, so start with that neutral head (without the blendshapes), and get a new body. (chop the head of that full mesh and throw that head away). Do a combine with that neutral head (the one that you know works). Just make sure you select the head before the body when you do the combine. Merge the verts at the border (making sure you use the pairs option and keep the max dist low just in case - in theory you can leave it at zero, but lets go with .01). Delete history. This new head-body combine will have verts in the exact same order as the original neutral head, because the combine just adds the body verts to the end of the list. So now when you add those head targets as a blend shape to this new head-body combination, the verts will line up correctly. You just need to uncheck the matching topology option so that maya doesnt complain about the differing vert totals. Like I said before, this is the best method. It is worth figuring out how to make it work.

Old 02 February 2013   #8
@djx: Ok, now I see what you mean by the neutral head. I used the head that I just extended from the body, not the head that I used to make blendshapes. I'll have to wait and see if this works. Thanks for clarifying.
Old 02 February 2013   #9
@djx: Ok, just used the method you posted earlier. It works! Brilliant way to get around this little problem. Thanks so much for your help.
Old 02 February 2013   #10
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