[C5] Rigging and Skinning : bones and setup

[Thomas]

This tutorial will explain how to build a bone structure to animate a character, it will also help you set up the influences for these bones to deform and animate your character.

To explain the title meaning, the Rigging is the step in which you will put all the bone structure and add the constraints (rotations limits, etc.) while Skinning is the setup of the influence of a bone on polygons around it, giving you the best deformation when you animate your bones.

At last, consider that this tutorial is only about Rigging and Skinning, and not modeling and animation.

Note:
This tutorial is for users who already know the basis of Carrara and not for beginners because all the steps around a specific feature are not explain in this tutorial. Please, refer to the manual.

[Thomas]

First part: Preparation.

As explained in the introduction, the modeling won't be done here. Open a character like the one below, modeled in Carrara vertex modeler or Hexagon (simple Box modeled character). For this exercise, choose/create a simple character, that doesn’t have a lot of polygons, it will be easier. You will see later that more vertices you have the more operations you will have to perform.

However some remarks about the modeling of animated characters: it will be deformed by bones so you have to take greater care of it in your modeling, around the deformation parts. Refine them a little bit more then the other parts of the body, like on the knees, elbows, to let them be deformable in a smooth way. On the screen captures below, surrounded by the red circles, some parts where the deformations will be apply.

If the model is imported from another software, the model should be unsmooth. Go to the modeling room, select all polygons (CTRL/Command+A) and in the Model menu, choose "Smooth edges" and validate (don't change the default values)

Now, in the property panel, Model tab, check the Smooth radio button, enter "0" for the "Modeling" value and "2" for the "Rendering" value. Like this, the 3D display will be faster and when the render will be generated, the result will be smooth.

[Thomas]

Second part: Materials

This step is optional, but it will allow you to have a better visualization of your model in the assembly room. We will only set different shading domains and give them a different color. Go to the modeling room select a group of faces, and in the property panel, Model tab, open the popup in the Shading domain section and click on the "New shading domain" (1). A popup opens (2) enter the name of this selection, like "Skin" and validate. For your information, Def_Surf_Mat is the default domain, set for all other polygons which don’t have any domain applied.

Do the previous steps for each part of your body. Below are all the domains used for the model.

Now, create the shader for the character. In the Shading room, set the different parameters like the steps below show it: Chose a layer list for the top Shader (1) Instead of "Multi Channel", choose "Basic layer" (2). Choose the name of the shading domain in the list on the right part of this level to which you want to apply your shader. Note that the Multi Channel is in the under level In the Multi Channel level, choose Color and set the desired color (3) Do it again for each shading domain by clicking on the small "+" on the bottom left of the editor (4) and doing again each steps above. If you click on the top level you can see on which part of the character (which shading domain) you have applied the different shaders and eventually, change them

A preview in color of our character, before the Rigging and Skinning.

[Thomas]

Third part: Bones creations

Here we go for one of the longest part of this tutorial! Before starting the creation of each bone, it is important to consider how your bones network will be build for your character. A structure with a Hierarchy will be created with parents and children and an error at the beginning will corrupt your entire model at the end. Keep in mind that this step is not easy, even for users who have good 3D skills. If you are not agreeing with your hierarchy and position, do it again, until you are pleased with it. First of all, the first thing to take in consideration is the parent for all of the hierarchy, which will move all the other bones connected when it will be moved, like a tree trunk which bring all the branches and leaves. In most cases, this bone is on a par with the umbilicus and is called "Pelvis". From this bones will start the legs, the spine, the head and arms. On the screen capture below, the arrows show you the direction of creation of each part of the bones hierarchy and in the red circles, the pelvis.

First, switch to an orthogonal view (front or left by example). Start by the pelvis and continue with the leg : pick the bone tool and click on the middle of the pelvis (1) to create the beginning of the bone, and click a second time, around the groin. If the size of the bone is too important, you can change it display size in the property panel, effect tab. Without quitting the tool, continue clicking to add your bones: third click for the knee, fourth for the ankle. Switch to a side view if you were in front view (or vice versa) and add the bones for the foot (2) Please, consider that the future rotation of your characters members will be around the bone starting position (these kinds of spheres). Then, with the move tool, move the bones to put them in a good position (3). Don't create the other leg, it will done later.

Second part, the spine: pick the pelvis bone, the Bone tool and add the new bones. We don't need to create the same number of bones as in our spines vertebra! Two bones are enough, but take care of their position. One on the waist (1), the other at the basis of the clavicle (2). The two reds lines show the axis of rotation for the new bones.

Let's continue with the shoulders, the technique is now always the same. Take care of the position of the shoulder bone, because it will impact on the future deformation when you will rotate it down or up (1). And finish by the hand (2). Seeing that the hands are like simplified gloves, don't create too many bones.

For the neck, take care of the basis (1) and the internal bones (2), to create more natural movements later.

A little tip to know: it is really necessary, sometimes, to add extra bones which help you later control your skinning and or potential deformations on your character, or more often, on animals. For the character, you can add two bones, on for each breast.

Now, we have half of the body, but before doing the opposite part, add some constraint to the bones.

[Thomas]

Fourth part: Constraints and symmetry

After a long part about creating the bones, now, it's time to define the constraints for each bone. Nothing really hard, but some methodology is required. As you already know, characters members have limitations about their rotations, like a knee which won't be able to rotate along one axis and only around 150-160°. Carrara allows this kind of limitation and if we want to have an easier animation later, we need to set them on most of the bones. First, before setting up the constraint, change the orientation of the axis of the bones. Because the constraints angles will be based on the local axis, then, we must orient them. Click on the "Lock child objects" icon, located on the left on the grids, views and utilities tools, on the window title bar (in the red circle on the screen capture below), which allows to rotate the bone ball joint without changing the children bones. Then, align your bone pivot to the bone itself, like the animated screen capture show it below. Do it for each bones of your character. Don't forget to switch off the tool before going on the next step!

Now, add a constraint to the bones: in the property panel, Motion tab, in the Constraint section, click on the "None" title (1) and chose the kind of constraint you need for the current bone selected. Below, the "Ball Joint" (2) has been selected, for the shoulder because it can rotate around three axis.

Once the constraint is applied, change its properties: the three circles and the small popup on the top of them, let you set the limitations of each axis of the bone. Then, you have to set the limits for each axis, or eventually, completely lock one axis. For the shoulder, all the three axis have to be limited: click on the small diamond to set the minimum and maximum limit. The triangle defines the default rotation of the current axis.

Obviously, it's not easy to find the good degree angle for each constraint. The best way is to pick the rotate tool, and rotate your bone around each axis and take a look at the constraint panel, and watch the values changing. Like this, rotating the bone on the higher and lower position, will give you the higher and lower angle. Then, you have to report them to the small diamonds. Once these limits values are applied, then, pick again the rotation tool and see if everything is working.

Below are some settings for some bone axis of the characters. For some bones, you can change the rotation order (drop down in the red circle). Then, it's time to define all the constraints for all bones!

Once all of the constraints have been defined, we have to do the symmetry of the existed bones. If it wasn't done before, it's because it's faster like that, you don't have to do twice the work to set the bones orientation and constraints. Before performing this operation, uncheck the "Use constraint" option (1) or you will have strange results. Then, select the shoulder bone (2) and in the Edit menu, chose "Duplicate with Symmetry" and select the good axis (3), X on the capture below, and validate. Carrara does the symmetry and automatically, connect the new shoulder to the spine!

Do it again for the leg (same operation as above) and when it's done, activate the "Use constraint option" once more.

To make it easier for future work, name all of the bones of your hierarchy and give if possible, the name which correspond to the "real" bone or body part and add right or left to the name. Avoid as much as possible default names like "Bones21", Bones18", etc.

The Rigging is now finished; everything should be ok for this part. Now, it's time to attach the bones to the polygons!

[Thomas]

Fifth part: Bones attachment and IK

It's time to start to play with our character! Select both Pelvis and character, and in the Skinning menu, choose "Attach Skelton"

The previous step was an easy one, now; it's time to do the real work! To verify the default parameters for the skinning, the easiest thing is to create a pose for your character. But don't do it at the 0 second time but at 1 second. Like this, you can edit your skinning at 0 and see the result at 1 second. And if you need to go back to the default position, the Skinning menu include a function to "Send bones to references position" Below, a pose for the character, done by only rotating the bones (don't move them!) done at 1 second. The result seems clean and deformations are well done by the default Skinning parameters.

Before continuing the skinning, a little bit more rigging: actually, to move the members of the character, only the rotate tool can be used and it's not easy to set a pose like this, especially if the feet need stick on the floor, etc. Then, we will use the Inverse Kinematics chains (IK chains), to create a kind of connection between the bones of a hierarchy (ex, from the shoulder to the hand)

IK chain creation is easy, only follow the steps in the good order: 1 - pick the IK chain creation tool 2 - Pick the starting bone of the IK chain to create 3 - Pick the destination bone 4 - A blue line, representation of the chain appears 5 - move the IK chain manipulator (the kind of blue cube) to move all the chain, and then, deform your character.

Continue the IK chain creation for your character, for each member to animate. Only use them for the arms and legs. Don't add it for the spine (only if you already master the IK and IK chains!) 1 - from the shoulder to the wrist 2 - from the wrist to the last bone of the hand 3 - from the hip to the ankle 4 - from the ankle to the last bone of the foot When it's done for one side, do it for the other side.

Now that the character is easier to move try again to set different poses and you may find some problems: on the screen capture below, the rotation of the arm generate a kind of pinched polygons inside the bust/torso. It happens because of the influence of the arm which is very important. In fact, the problem has been over-exaggerated to show what can happen! On the next part, we will see how to correct this problem. .

[Thomas]

Sixth part: Skinning, bones influences and Weight Painting

Before editing the bones influence of the character, set different poses, like sitting, jumping, etc, but without changing the default pose at 0 second. Like this, we can edit the skinning without corrupting the default pose.

Double click on the character, to go to the vertex modeling room and switch to the Animation mode (button in the red circle)

The modeling room displays the model at the actual frame. If you switch from your initial pose to the first pose it will be easy to see the deformation of your model and then, correct them more easily. The arrows below show some problems.

The first way to correct the bone influences over the polygons, is to select these polygons. On the Bones tab, in the property panel, you can see which polygons are "connected" to the current selection (1) (vertices, edges or polygons). To change the current selection position (2), move the sliders of the associated bones (3).

In some specific cases, changing the influence can't help defined the good deformation, simply because a bone attraction is missing for the current selection (1). Then, in the "Add Bone" drop down menu, add the needed bone (2) and at last, change the new bone influence (3)

The other way to change a bone influence, is using the new Carrara weight painting tool. First, select the tool (1) and in the property panel, chose the bone influence to edit (2) and choose if you want to add or remove some influence from this bones to the polygons (3). Your object displays a gradient from yellow, orange to grey. Yellow mean a maximum influence. You can also set different properties for the brush (4) and activate the 3D brush (5). But this last option can generate unpredictable results, then, it's better to inactivate it.

Below, the weight painting of the pelvis in animation. Easy, no?

For the knee you can, as previous steps, set the bending and adjust it deformation. Now, you should understand perfectly why using pose for the skinning is useful! Do it for each bone of your body, to validate the deformations and bending of your body parts. Change of poses to study each transformation. Keep in mind that the weight painting tool doesn't work in symmetry mode. What you will do on the left part have to be done on the right part, and vice versa!

[Thomas]

Seventh part: "Setup"

If all the steps were done without any problem, your character should be ready to animate. But if you start to animate it, you may have several problems: two manipulators for each hand or foot, it's hard to select the pelvis bone, etc. Then, it's time to create assistants or "manipulators" to make easier the animation process.

In the vertex modeler, create a kind of full hand (1), do two internal extrusions (2&3) and remove the internal polygon (4). You can tweak some polygons to have something nicer.

Go back to the Assembly room and set the hot point of this kind of hand on a par with the wrist and select the bone of the wrist and the simplified hand (in this order). Go to Edit>Align function, select each axis in the dialog box and validate. You should have your simplified hand aligned to the hot point of the wrist bone. Now, select the simplified hand and with the rotate tool, align it with the bones of the hand.

Now, in the scene tree, select the IK chain of the wrist (1) and drop it to the simplified hand. Do it again with the hand IK chain (1): you have created a new hierarchy (2), where the simplified hand is the parent of the two IK chains!

Below, an animation of the hand manipulator and the IK chains manipulators. Moving the hand manipulator moves the two IK manipulators, but because of the hierarchy and IK, you can move each IK chain independently! Try it and you will love it!

Do it again for the other hand and the feet. Don't forget to adjust the hot point of the modeled manipulators, to be sure that rotations of the manipulators will fit the bones rotations!

Do another big manipulator, a kind of empty circle for the pelvis. Drag the pelvis bone hierarchy (in fact, all the character hierarchy) other the manipulator in the scene tree (1), to create a hierarchy as made previously for the simplified hands (2)..

For this manipulator, apply a visible shader color (1) (like the green in the screenshot), put the alpha channel value to 0 (2) (not visible in the renders) and in the property panel, uncheck the Casts Shadows and Receive shadows boxes (3).

Now, it's time to animate! Bellow some tests made in a couple of seconds, with the help of the manipulators!

This tutorial is now done. As you see it, it's a long run for a full character skinning, rigging and setup, but when it's done, how easy it becomes to animate! Now, it's time for you to apply this on all character you will create!

[JuST]

Wow really cool! Thank you very much Thomas for this piece of work! Exactly what I do need!

[mykyl1966]

Came at exactly the right time for me also.

Cheers

Mike R

[cartoonMike]

Thanks Thomas!

I've looked at this tut at the French section and have read the Google translation, all half-page of it :>

Very helpful and now the manipulators make sense. What a great holiday treat this is!!

m!ke

[corzair]

Great stuff, I needed something like this also
Thanks Thomas!!

Much Appricated

[Thomas]

I only hope my english is understandable I'm glad you like this tutorial!

[akenw]

This is by far the best tutorial on character rigging and bones that I have found. You're awesome! Thank you so much!



Ken

[mon_stdnt]

for the IK SET UP, does it work all with fingers? Do I have to the chain w/ every finger? and how would I do the manipulator hands for it?