Modeling for animation – Body

Character modeled for animation is modeled to deform well in animation. This article desbribes benefits of edgeflow and edgeloops and the general ways to use them on a human/humanoid torso and limbs.

To begin check out  my article on surface flow, if you already haven’t.   And then, to go futher we need to understand edgeloops.  Quoting guru Bay Raitt:

An Edge Loop is an interlocking series of continuous mesh edges used to accurately control the smoothed form of an animated subdivision surface.

Edgeflow and Edgeloop are essentially the same thing.  Flow as a loop separates areas, defines shapes and directs edgeflow. You use loops in places where major deformation happens in animation.

Overall edgeflow within each looped area matters, too. Idea of a good flow, as I see it, is that when stretching or compression happens the polygons are already aligned towards the change.  Then the deformation is usually problem free.

The general advice is to model the flows following the main muscles under the skin. It can get needlessly complex considering how many mucles move a human body.  Some people have been obsessing over edgeloops for years.  Luckily you only need loops for main muscle groups or body masses.  Think what main masses/muscles move in a character and how. Direct the surface to flow along them and form loops around them.  The loops may be interlocking and that’s all good.  Then they mix and crease together better.

What if you want superb muscle definition?  Much of the missing detail can be added with displacement maps(from Zbrush, Mudbox and the like), and when the base moves correctly the displaced ‘muscles’ on it move mostly alright, too.   Though if you want realistic flexing muscles, you need a heavier setup – but this gives a good base to start from.

modeling for animation - body loops and flowsWhat are the Main Masses moving in a human/humanoid?

  • Back of a character bends below the chest.  You need loops going around the torso.  Chest bends too, even the rib cage below deforms, however the musle masses on chest and shoulder & back-area have more effect on the shape change, shoulder having clearest effect. You should have flow from chest directed to flow over the shoulder and to the back. Please note my optimization here has lead to a pole, a 6 edges intersection, in the middle of the back. It is not troubling me, but if you build similiar mesh you may want to add few polygons in that region to get rid of the pole.
  • The arm-mass connects to the shoulder and the problem area is over the arm-socket.
  • Head and neck moving about affects the area around the neck and some ways to the back.
  • Legs move the buttocks as well.   The mass movement limits to top of the hip bone, pretty much.
  • With arms and legs the problematic bits are knee and elbow both. Masses of back- and forelimb come together and separate there.  The loops help to give more mass on the outside part of the bending limb, giving material for both parts that bend away and a centerline that stays more or less in place. You may get by with a tube-like structure here for cartoon-characters where things aren’t that exact OR by having many loops that you carefully weight to bones to deform just right.

model    for animation - x-loop

Highlights and edges show the flows I like to use for this model.   Disclaimer: Please note this is definitely not the only way to do this, just A way.  You can get by with less loops, more loops or with different loops. Whatever works, works – I find these work for me.

The loops above, in limbs and at the top of the shoulder, are variations of a very useful x-loop.  See the diagram of a more complete version of it.

Also here is another version, a knee with more ‘mass’ left in.modeling  for animation - knee variation You can do varied X-loops.

Do you find this helpful?  Please let me know.  And if you don’t think the shown flows help animation, please give critique.

Read more about edgeloops here  http://web.archive.org/web/20120422232142/http://www.3darts.com.br/tutoriais/edge_loop.php. Original article has expired but can still be found in Google archive(Thanks Terry). It is in Portuguese.  Here is a translation to English.

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