Skin Wrapping in 3ds Max - Part 1 - Variations
In this tutorial, you will learn about the Skin Wrap tool and deforming objects tool. It is flexible enough to have a variety of uses but what it's really great at is transfering skinning data from one character to another.
- Recorded in: 3ds Max 2012
- This tutorial is intended for use with 3ds Max version 2012 or higher.
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Skin Wrap is usually used to have a low-resolution mesh drive the animation
of a high-resolution mesh.
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Practically however, its use is somewhat different.
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For example, its application in the gaming industry is to use Skin Wrap
to transfer skinning data from one character to another.
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Many times in a gaming project, you have to duplicate characters
that look somewhat alike but with slight variations.
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Two soldiers may look similar but one may have an extra pouch on his uniform
while the other may carry an extra gun belt.
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Other variations may include fat, medium or skinny characters in a crowd.
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As long as these characters have the same general build, meaning general height and proportions,
then you can transfer skinning data effortlessly.
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In that case, they can all share the same skinning template and rig.
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It is important therefore to be able to "recycle" your work,
given that properly skinning a single character can take hours or even days.
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After properly skinning a single character, you can then transfer that information
in a matter of minutes or even seconds using Skin Wrap.
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The scene you will be using here has a few objects, mainly characters, but also a biped skeleton.
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The main character, named "Full-Body" has already been properly skinned to the Biped skeleton.
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The Biped at this time is in Figure mode, but if you exit Figure Mode,
you can see the animation used to test the skinning.
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Go back into Figure Mode to get the initial pose back.
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This particular example is using a Biped skeleton but Skin Wrap works equally well
with any type of skeletons, be it Biped or CAT or simple Bones.
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Select the two characters to the left and hide them; you'll only use them in Part 2 of this series.
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Zoom in and take a look at the remaining characters.
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The main (skinned) character on the left and the one in the center are very much alike.
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They have the same topology and you can tell that one was used to create the other.
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There are some slight variations such as a pouch and a bandage on the character's right leg,
a knee pad on the left,
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the torso has some wacky protruding design and there are some extra laces on the left forearm.
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The warrior character on the extreme right is totally different though.
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The topology is nowhere near and you can see that it was designed and built independently.
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However, in terms of general height and proportions, the two characters do have something in common.
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Let's take one problem at a time, select the warrior and hide it.
You'll concentrate on the two characters with slight variations.
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If you select the main character, you will notice that its pivot point is between its feet,
located at world coordinates [0,0,0]
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This is typical when you model a character and will make it easier to position
the other characters you want to skin wrap.
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Select the "Variations" character and notice that it too has its pivot point between its feet.
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For Skin Wrap to work, the two objects have to be on top of each other.
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Relocate the character to [0,0,0] so that its sitting on top of the original.
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Notice also that both have the same initial pose. This is important for Skin Wrap to work properly.
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In wireframe mode, notice also that besides the obvious variations, like pouch and chest logo,
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there are some less obvious variations around the shoulder areas.
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All this to say that the two models do not have to be exactly identical.
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With the Variations model selected, go to the Modify panel and apply a Skin Wrap modifier.
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Before choosing a Control object to drive your mesh, take a look at some of the options.
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You can drive the deformation by Vertex or Face types.
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Which one you choose will depend largely on the object at hand and your personal preference.
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Many riggers in the games industry seem to favor Face Deformation, so go ahead and use that one.
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The Falloff value ranges from 0.001 to 10.
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This determines how vertices in the animated (or Control) object affect or pull vertices
in your selected object, referred to as a Base object.
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However, when using Face Deformation, it is often best to use a rigid transformation
by setting the Falloff value to 0.001.
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Next, you define a Control Object, in this case the Full-Body character
that is already skinned and animated
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In the Parameters group, click Add.
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Select the Full-Body character underneath the one you are working on.
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As 3ds Max processes this info, you get a status feedback in the bottom left corner of the screen.
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When it reaches 100%, make sure you right-click to cancel Add mode,
otherwise you may accidentally click another object and add it to the list.
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The process is now done.
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To test how Skin Wrap worked, select the biped's head and go to the Motion Panel.
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Exit Figure mode.
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Scrub the animation to see the results.
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Between frames 0 and 650, verify that the lower body worked correctly.
Notice how nicely the kneepad is behaving around frame 260.
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Check out the Torso between frames 660 and 1100.
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If you had to manually skin that chest logo, you would have had to spend a good deal of time on it.
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Hands, fingers and forearms can be checked between frames 1150 and 1950.
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As long as the Variations character is skin wrapped,
changes you make to the Control character (Full-Body) will be propagated to it
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At frame 1900, say you want to adjust the deformation of the forearm.
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Select the Full Body character. In the Modify panel, click Edit Envelopes
and select the 3rd ring of vertices from the wrist.
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Highlight the L_Forearm_2_Roll envelope in the list
and try some changes to the Abs. Effect value.
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Notice that it updates both the Control object and the Base object, the one you skin wrapped.
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Once you're happy with the changes, you want to go back to your initial pose.
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With biped, it's a question of selecting a part of the skeleton and going into Figure mode.
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At this point, you can make your Base object (named Variations) independent
from the Control object driving it.
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With the Variations character selected, go to the Modify panel and click the Convert to Skin button.
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You now have a new Skin modifier with all the proper envelopes and vertex weights
assigned to your character.
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Notice how the Skin Wrap modifier has been automatically turned off.
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In fact you can now select it and delete it.
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You can now test the animation again.
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If there are any skinning areas that require tweaking, you can certainly address them.
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It will only take a fraction of the time tweaking a few vertex weights here and there
rather than having to skin this character from scratch.
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Skin Wrap probably just saved you a couple of days on your schedule.
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Hide the Variations character and from the Selection Sets list, choose Warrior.
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Click Yes to dismiss the warning.
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Make sure the biped is in Figure mode so that both characters are in the initial pose.
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As mentioned earlier, this character is quite different from the main Full Body character.
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The only things in common are general volume and proportions.
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Place the warrior character at [0,0,0] and repeat the procedure to skin wrap it
to the Control object.
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Select the Biped's head and exit Figure mode.
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Isolate the warrior and test the animation.
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For the most part, it's really not too bad at all.
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There are certainly some areas that require a bit of attention
such as under the arm pits noticeable between frames 1150 and 1950.
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The wrists also could use some adjustments, and that's noticeable around frame 1780.
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The head seems most problematic between frames 2250 and 2500,
but that's only because the warrior character actually has a head.
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The original Full Body character didn't. Skin Wrap didn't know what to do with that.
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The point is all these are simple tweaks that can be done
in a fraction of the time it takes to skin the warrior character from scratch.
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Go back to the original pose by selecting the biped's head and going into Figure mode.
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Select the Warrior character and convert Skin Wrap into a full Skin modifier.
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Delete the Skin Wrap modifier underneath it.
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Go into Edit Envelopes and select all the skin vertices that make the head.
Do not select the ones on the neck.
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Select the Bip001 Head envelope and set those selected vertices to an Abs. Effect of 1.
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This will ensure the head vertices are weighted to follow the biped's head only,
and no other bones.
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Similarly, you can fine tune the other areas such as wrists and armpits.
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Tweaking a few vertex weights here and there is a matter of minutes.
Skinning a full character from scratch is often a matter of days.
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Go back into Figure mode when done.
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Hide the warrior and from the Selection Sets menu, choose LODs. Dismiss the warning.
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In the next movie, you'll experiment using Skin Wrap with LODs (Level of Detail objects).