This is the fourth tutorial in my four part series dealing with character animation. These tutorials are targeted for beginners wanting to learn the basics of modeling, uvw mapping, texturing, rigging, and creating a cute 3d monster. In this fourth part we’re dealing with character rigging. You’ll learn the basics of using the Morpher and Skin modifiers to manipulate and deform a simple character. Character rigging can be a tough subject for beginners but I’ll do my best to keep things as simple as possible. I’m using 3ds Max 2011.
In 3d animation, character rigging means the process of preparing the character for animation. The idea is to use special helper objects and modifiers to prepare a set of tools that make the animating process as easy as possible. We’re going to rig the character by using the Morpher modifier for the facial animation and the Skin modifier (in conjunction with bones) for the rest of the body. In the picture below you see a character pose you can be easily do after completing this tutorial.
The Morpher modifier is commonly used for lip sync and facial animation. The Morpher modifier deforms the original object according to predefined target objects. The biggest task is the creation of the target objects ( morph targets ). The modifier itself is really simple to use.
Let’s create the morph targets for our character:
Now we have one morph target and that’s enough for the sake of this tutorial. If you are about to create some serious facial animation, you need more morph targets. Just create more copies from the original and create expressions like smile, amazement, blinking eyes and so on. It’s often a good idea to create separate targets for eyes and mouth and separate targets for the left and right side (like wink) as well to have maximum control over the expressions. The Morpher modifier lets you combine the expressions of several different morph targets.
Now select the original monster model and try the Morpher modifier:
Tip: Turn ‘Use Limits’ off in the ‘Global Parameters’ rollout to go beyond the 0-100 range. Try for example negative values to get some interesting ( and maybe even useful ) results. Remember also that channel percentages can be mixed when you have multiple morph targets.
While the Morpher modifier controls the facial expressions, the bones control the rest of the body. Let’s create the skeleton:
Now we have four bones that are linked to each other. The first bone is the parent of the second, the second is the parent of the third, and so on. If you move the first bone the whole chain follows. You can also double click on the parent to select it and all its children.
Next we’re going to create bones for the spine and the head:
Open Bone Tools (), activate the ‘Bone Edit Mode’ and move the spine bone to meet the first bone of the leg like in picture below. Close the Bone Tools.
Next we’ll create the arm bones. This time we want to link the arm bones to the spine so start creating the bones by clicking on the spine bone. Create four bones ( plus the nub bone) for the left arm like in picture below.
Now we have all the bones we need and we just have to fit them inside the character. Go to the left viewport, select all the bones and move them to the center of the character. Rotate the bones like in picture below. Notice how the knee bends. We bend the bones now to make them work better with IK.
I wasn’t really sure how I should rig this weird monster character so I did the leg bones pretty much like I would for a human-like character (except for the fact that there is only one leg). You can also create two “legs” inside the monster if you want to make it “walk”. It all depends on how you want your character to move. Does it move by flying, jumping, crawling, walking, or by all these means?
Go to the top viewport and rotate the arm bones so that they fit inside the character. Make sure the arm bends a little.
Select the whole arm by double clicking on the clavicle bone (the bone between the spine and the arm). Use the mirror tool () to make a mirrored copy of the arm ( make sure to make a standard copy, not instance or reference ). Position the new bones like in picture below.
We still have to link the right arm to the spine:
Now the skeleton is complete, but let’s create one more helper object to serve as a master that is used to move the whole skeleton. Create a dummy () and position it exactly where the spine bone and the first leg bone meets. Check the position in both the left and front viewports.
Use the ‘Select and Link’ tool () to link the spine bone and the first leg bone to the dummy. Now if you move the dummy, the whole skeleton should follow. Try this to make sure everything is ok and finally undo the move.
As a final step, link the eyes ( if you have them ) to the head bone. Now the eyes stay in place whenever the character moves.
Now the skeleton is complete and we go on with inverse kinematics. Inverse kinematics if often assigned in the character rigging process, especially for the legs. Let’s assign inverse kinematics to enhance our rig:
Next go to the front viewport and assign IK also for both arms. Make the IK chain from the first bone of the arm to the nub bone ( Don’t touch the clavicle bone ). Test how the arms work. They should work well in the top viewport.
Now all the IK solvers have been created. At the moment you can’t rotate individual bones in the IK chain. To be able to do that, select the IK handle, go to the motion panel, and click ‘Enabled’ in the IK Solver rollout. This is the on/off switch for inverse kinematics for the selected IK chain. This button can also be animated so the animator can easily switch between inverse kinematics and forward kinematics ( just rotating the bones in the chain) while animating the character. Leave it on for now.
As a final thing, try to move the green dummy to see how the character responds when inverse kinematics is in use ( undo afterwards ).
Next we’re going to enhance the rig even further to limit the rotational movement of the bones:
Now the leg bones can rotate only along Y axis and within limited range. Try to move the leg with the IK handle to see the difference. Now It’s up to you whether you want to set the limits for the arms as well or not. You might want to come back to this step after the skinning process to see the movement of the character while trying out different values.
Character skinning is the process where we define how the model responds to the movement of the bones. We’ll use the Skin modifier for that purpose. Let’s unhide the character () and go on with the skinning process:
Let’s repeat the process and apply appropriate radius values for the rest of the bones (). Make sure you change only the radius values of the outer bounds. ( ):
Now the skinning/vertex weighting process is done. Deactivate the envelope sub-object level and try to rotate each bone to see how the character deforms. Try also the IK handles and the master dummy. I recommend undoing all the rotations afterwards to keep the neutral pose.
This is an optional step. Just some theory and tips. If you are lucky you can get pretty good results just by adjusting the envelopes sizes, but there is often a need to fine tune the behavior of individual vertices as well. To weight vertices manually:
( The weight value of a vertex (Abs. Effect) always amounts to 1.0. This value can be divided between several bones. For example, vertex’s weight could be 0.7 for bone-1 and 0.3 for bone-2. In that case the bone-1 would have much higher influence on the vertex. In other words, the vertex would follow the movement of bone-1 much more than it would the movement of bone-2. )
Tip: The weighting/skinning process can be made easier by animating the bones. Just animate some natural bone movements. At first, the character will look ugly and distorted but keep in mind that as long as you keep the neutral pose in keyframe 0, nothing will break. You can always reverse everything by going to frame 0 and removing all the keyframes. The benefit of the animations is remarkable. You can see the deforming character while working on envelopes just by moving back and forth on the timeline.
That’s my take on character rigging. Let’s continue in the comments! In case you’re wondering, I made the light and glow effects in Photoshop.
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