Shrinkwrap on a Rig

Hello and welcome to my first tip-top-tool-tip.
Here is a generic method for using a shrinkwrap modifier on any rigged mesh.In this demo i use a fully rigged character template from Avastar.
But you actually can also use any other rig here, like avatar.blend for example.

Transcript

Hello and welcome to my first tip-top-tool-tip.
Here is a generic method for using a shrinkwrap modifier on any rigged mesh.

In this demo i use a fully rigged character template from Avastar.
But you actually can also use any other rig here, like avatar.blend for example.

And this is the very simple skirt that i made in another tutorial.
I created a cylinder and applied a shrinkwrap modifier,
where the shrinkwrap target is set to the skirt template of the character.

Now i want to attach my new mesh to my rig,
but i also want to keep the shrinkwrap modifier intact.

Lets hide the skirt template layer here for a moment.
and enable smooth shading for the new skirt.

Now lets attach the new skirt to the rig with
an automatic generation of the weight maps.

Ensure that you are in object mode,
and the skirt is selected.
Then shift right click on the armature?

Now navigate to: object, parent, set, armature deform.
finally select the option labeled as: with atomatic weights.

Now the mesh has been attached to the rig,
and the weight maps have been generated.
Lets check if it works.

select the rig,
go to pose mode.
And now move the bones.

Well, it worked, but the result is ugly.
The reason why this happens can be found in the modifier stack of the skirt.
We see that the shrinkwrap modifier is on top.
That is, it is calculated first.
However the target of the shrinkwrap modifier is itself modified by the armature.

Let me unhide the template skirt,
and disable the armature modifier of the new skirt for a moment.
Now you can see better what happens here.
And you see that our new skirt is now shrink wrapped around
the already posed skirt template.
When i now reenable the armature, the already deformed
skirt gets deformed again,
Hence the armature modifier is effectively applied twice to our skirt.

So, lets move the shrinkwrap modifier down below the armature modifier,
Now our new skirt is first bended just like the skirt template,
then shrink wrapped to the skirt template.
Hence now the armature modifier is effectively only applied once.

moving the shrinkwrap modifier down on the stack helps a bit,
But we run into many more problems as soon as we start moving the arms.
Now the skirt gets more and more spiky, and attaches to the arms
and hands.
This is due to the nature of how the shrinkwrap modifier
actually finds its target surfaces.

And here is the trick how you can fix that.

First reset the character to T-pose by pressing: “a”,
You might need to press the key twice to select all bones.
then press: alt,r, to reset all rotations.

finally go back to object mode.

Now create two linked copies,
by first selecting the skirt template,
then press: ALT, d,
followed by an immediate left mouse click.
Now select the upper body,
press again: alt, d, followed by left click.

We will see in a moment
what benefits we get from using linked copies here.
But first let us move the copies to another layer for getting
our setup better organized.

And here comes the important part of the trick:
Remove the armature modifiers from the copied objects.
When we pose the character now,
then the copies no longer get influenced by the bones.
Let me demonstrate that by selecting layer one and layer 2 at the
same time. Then move the bones a bit.
You see that the just created copies are not influenced by the
bone movements.

Now lets turn back to the new Skirt.
open the modifier stack.
and now change the shrinkwrap target
and the auxiliary target
to point to the just created copies.
And finally move the shrinkwrap modifier up above the
armature modifier.

So, since the shrinkwrap target is no longer influenced
by the pose as it was before,
now the shrink wrapped skirt is also static.
Hence the armature modifier now works on a well defined static Mesh,
and we end up with a clean pose.

Now we only have to tweak the weight maps a bit and our skirt is done.
I will get back to this in my next tool tip.

But hold on, i made linked copies before,
and i promised to tell you why that makes sense,
why i did not make independent copies by using SHIFT, d.

Now here is the explanation:
Our model uses shape keys,
So we can modify the model by using shape sliders
for all model parts, also for the skirt template.

Now i have used linked copies,
thus the shape sliders also influence the copies.
And since the copies are shrinkwrap targets of the new skirt,
the skirt is now also influenced by the shape sliders.

That is neat, isn’t it ?
thank you for watching.

5 Enlightened Replies

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  1. Avastar-1-dev-625 is available « | August 27, 2012
  1. fred burg says:

    where can I buy avatar for blender 2.7

  2. Melanie says:

    Hello Gaia,
    Thank you for this tutorial, the red skirt you are using, is that included in the avastar? It seems well weight painted, much more than the one I have in Avastar, would it be possible to get a copy of that template?

  3. dq darwin says:

    cool ^_^

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