The rigging process - Part 2 - Building a custom rig

            In the last post ‘Rigging – Part 1’ I have concluded that the basic biped rig system 3DS Max has to offer is not suitable for this type of project, so I’ve decided to build my own custom rig (skeleton). Doing so has several advantages over using the pre-set rig, such as the ability to assign custom controllers, custom IK and FK chains, constraints and more.

            Using the ‘Bones’ systems tool, I have first created the body skeleton of the model starting with the first spine bone and moving up towards the head. Although you can have as many as 6 spine bones in total, during my research I have found out that 3 spine bones are usually enough for animating a human character model, such as mine. As such, I have given the spine a realistic curvature that follows the posture of the model, as it will help with setting up the IK chains at a later point. I did not forget to accurately name each separate bone as every ‘individual body part must be named for formal understanding and recognition in the subsequent steps’ (Bhati, Waqas, Karbasi, & Mahesar, 2015). For that, I have used the 'Rename Objects' tool available under the 'Tools' menu.

(Side-view of the spine)

            The pelvis bone was the next to be created, keeping in mind that the bone needs to be facing downwards, opposite to the upwards direction of the spine bones. That is because in animation, much as in real life, the pelvis is closest to the ‘centre of gravity of the human body’ and also ‘it is the centre of weight distribution for the entire body’ (Maestri, 2016). Therefore, the pelvis bone is the root of the rig.

(Mirrored leg with flipped bones)

            Moving on, I have structured the left leg of the model with the thigh, knee, ankle and toe bones. I kept in mind that the knee bone should be always bent to the back a little, in order for the IK solver (that will be applied later) to allow the leg bend in a natural way, and not backwards. After I was pleased with the position and rotation of the bones, I have used the ‘Bone Tools’ interface to mirror the left leg on the X axis and thus create the right leg. However, because the bones were mirrored, they were now flipped inwards. Quickly reversing the sizes of each separate bone solved the issue. The legs were then linked to the root (pelvis) using the link tool.

            The arms were realised in a similar way to the legs, starting with the clavicle, shoulder, forearm and ending with the wrist bone. I have then copied the shoulder, forearm and wrist bones twice. The first copy was then reduced in size and recoloured as it will be used for IK controls. Similarly, the other copy was enlarged and it will serve purpose for FK controls. All three bone chains are overlapping, as seen in the picture below.

(Red - Roll bones; Blue - FK bones; Yellow - IK bones)

            The bone segments (in red) on top of the forearm and the shoulder are ‘roll bones’. They’ve been created by copying the shoulder bone and slicing it to about half of the initial size using the ‘Refine’ tool under the ‘Bone tools’ menu. The forearm roll bones were created exactly the same, but instead the bone had been sliced into three equal segments out of which the ones closest to the wrist have been kept. The roll bones will be useful at a later point during the skinning phase in order to mimic the slight rotation of a real humans’ forearm (and wrist) bone(s) and the skin deformation that comes with it. Upon completely structuring one arm the other one was mirrored into place by the same methods used for the legs. The clavicles were ultimately linked to the chest spine bone.

            Due to mirroring the right leg and arm, the X and Z axis rotations were inverted, which meant that the two arms were rotating in contradictory directions. In order to solve the issue, I have selected the mirrored arm and leg and while only affecting the pivot points, I have given them a relative world rotation of 180 degrees. Now the limbs were rotating in the same direction, two by two.

            After finishing the arms, I moved on to the hands. I have used the same methods as the ones explained above. Each hand has 5 fingers comprising of 3 bones each, and a nub on the tip of each finger. The palm is a bone on its own to which the 5 fingers are attached. The hands were then linked to the wrists using the link tool.

            At the end, I had finished creating a full custom skeleton for the model I plan on animating. Controllers, handles and such helpers will be added at a later stage. Taking a moment to reflect on the work discussed in this blog post, I can say that although the actual creation of the skeleton is not  hard, there are loads of small issues that can stop your progression. However, those apparent issues have simple solutions that can put you back on the track incredibly fast.

References:

Bhati, Z., Waqas, A., Karbasi, M. and Mahesar, A.W., 2015. A Wire Parameter and Reaction Manager basedBiped Character Setup and Rigging Technique in 3Ds Max for Animation. International Journal of Computer Graphics & Animation, 5(2), pp.21–36.

Autodesk 3ds Max Learning Channel, 2012. Creating a Skeleton in 3ds Max - Part 4 - Arm Bones. Available at: <https://www.youtube.com/watch?v=W13OxAM8F8w&list=PLnKw1txyYzRlxh1-BT4CifPXC5TBg2vUd&index=8&t=0s> [Accessed 28 Nov. 2018].

George Maestri, 2016. How to Properly Rig Your Characters for Animation | Hierarchies and Character Animation | Peachpit. [Learning] How to properly rig your characters for animation. Available at: <http://www.peachpit.com/articles/article.aspx?p=483793> [Accessed 27 Nov. 2018].