[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!