In some cases, after you’ve skinned a character, you might need to make adjustments, either to the character mesh (for example, adding details such as pockets or increasing mesh resolution for more realistic-looking joints) or to the rig, such as modifying the structure. This section shows how to recover from such a situation without having to re-skin the character.

This section also covers using Skin Wrap to transfer a skinning solution to a similar character with a different mesh resolution.

Set up the lesson:

• On the Quick Access toolbar, click (Open File), navigate to the \character_animation\skinning\ folder, and open the file modifications_post_skin.max.

  This scene contains the final Emma character with two modifications:

  First, a patch has been added to the upper arm of the character mesh:

  

  Second, the thigh bones have been subdivided to lend the rig more articulation:

  

Let the Skin modifier automatically adjust for mesh changes:

You can follow along on the included character or simply use this as a procedure for your own project.

1. Expose the rig, if necessary, and return to Setup mode by selecting the CATParent (the triangle under the rig), going to the Motion panel, and clicking (Animation Mode) so the button image changes to (Setup mode).

   The rig snaps back to its original position.

2. Go to the Modify panel, select the character mesh, and turn off the Skin modifier.
3. Go to the Editable Poly level in the modifier stack and make your changes to the character mesh.

   For example, in the included scene, you could delete the shoulder patch and use Bridge to replace it with clean quads.

4. Turn the Skin modifier back on and re-enable (Animation mode) for the rig.

   The Skin modifier weights any new vertices automatically according to surrounding existing vertices.

5. Scrub through the animation and tweak the auto-generated weighting as necessary.

Let the Skin modifier automatically adjust for rig changes:

This method uses a special function in the Skin modifier that toggles whether rig changes affect the character mesh.

1. Go to the Modify panel, highlight the Skin modifier, and on the Advanced Parameters rollout, turn off Always Deform.
2. Turn off the Skin modifier and set the rig to Setup mode.
3. Adjust the rig as necessary. For example, you might have been handed a rig in which the leg bones were not of the same proportions. In this case, you’d lengthen or shorten a bone in one of the legs.
4. After you finish making changes, select the mesh, turn on Always Deform, and then turn the Skin modifier back on.
5. Select the CATParent and return to Animation mode.

   The rig changes do not cause any unwanted deformation of the character mesh.

   NoteThis method is not foolproof. If, for example, the character is properly skinned and you drastically change the proportion of the bones in one leg, that leg’s skinning will probably need adjusting. This is mainly for instances where the skinning is correct but the rig does not conform to the mesh in an isolated area.

Transfer skin to another mesh:

A quick way to transfer a skin map from one character to another that uses the same rig is with the Skin Wrap modifier. Basically, Skin Wrap uses location to transfer animation from one object to another. It does not depend on topological similarities.

1. Open the final version of the Emma scene file (configuring_skin_finished.max), turn off the Skin modifier, and place the rig in Setup mode.
2. Open the final version of the Emma scene and use Tools menu Clone to copy the mesh to two new objects. Name them Emma_LowRes and Emma_HighRes. Move them to either side of the original.
3. Select Emma_HighRes, delete the Skin modifier, and apply the MeshSmooth modifier. On the Parameters rollout, under Separate, turn on Materials and Smoothing Groups.

   This produces a model with about four times the number of vertices.

4. Select Emma_LowRes, delete the Skin modifier, and apply the ProOptimizer modifier. On the Parameters rollout, click Calculate, and then set Vertex % to 50.0.

   This produces a model with the same look but about half the number of vertices. It’s suitable for a mobile 3D application or for a character that’s viewed only from relatively far away.

   An important requirement of Skin Wrap is that the objects between which you’re transferring animation be in close proximity. You’ll start with the low-resolution model.

5. Move Emma_LowRes to the same location as Emma, which is (0,0,0).
   TipIf you previously moved it on the X axis only, just right-click the spinner to the right of the X field on the status bar.
6. Apply the Skin Wrap modifier to Emma_LowRes. On the Parameters rollout, click the Add button, press H to open the Pick Object dialog, and select the Emma object. Right-click to exit Add mode.

   There will probably be a short delay while Skin Wrap performs its calculations.

7. Right-click in the viewport or click the Add button again to exit Add mode.
8. Select the Emma object, turn on the Skin modifier again, set the rig back to Animation mode, and hide the object and rig.
9. Play the animation. It plays back perfectly.

   The process is the same with Emma_HighRes, except that applying Skin Wrap takes longer because of the greater complexity of the mesh.

Save your work:

• Save the file under a new file name.