Preparing the model for animation - The necessary steps



After establishing the necessary skills for a 3D Animator job role, I had to get a better understanding of what the processes involved in animation were and how do they work. Upon research, I have found out that there are two things that needed to be done in order to prepare the 3D model for animation. Those two processes are, in order:

o   Rigging the model
o   Skinning the model

Rigging a model of any kind, be it a bipedal human or a different kind of creature, implies creating a ‘rig’ for the said model. A ‘rig’ is in its essence the skeleton of the chosen model. So, 3D rigging is ‘the process of creating a skeleton for a 3D model so it can move’ (Pluralsight, 2014). The process usually takes place first as without a rig the model can’t be moved or deformed, so it cannot be animated either.

In order to create and enable control of a skeleton, the users are able to use a variety of tools. The tools I am interested in are:

1.      Joints – the joints are the bones of which the skeleton is composed of. They act as points of articulation that enable the user with control over the different parts of the skeleton. The user can therefore rotate, translate and effectively deform the model by using these joints. The skeleton rig is placed inside the 3D model of the character.
2.      IK (or Inverse Kinematics) – by using and IK system for, say, the leg of a human model, when the user moves the foot of the model using the ankle joint the rest of the leg follows and contracts or extends according to the position of the foot.
3.      FK (or Forward Kinematics) – the FK systems give the animator more control over the poses of their model, but also takes more time. It functions in an opposite way to the IK systems: if the animator moves the hand of the model the rest of the arm will not follow, meaning you have to independently move the shoulder, elbow and wrist joints in their position.
4.      Control curves – the control curves are basically curved shapes placed outside of the model that allow the user to control (rotate and translate) joints easier without having to hide the mesh and discover the skeleton each time the movement of a joint is necessary.
5.      Constraints – ‘constraints limit the position, rotation and scale of an object based off of the attributes of the parent object’ (Pluralsight, 2014). Particularly useful when using IK systems or control curves, whatever the parent joint does the child (joint) follows.

           The skinning process (also known as enveloping) binds the skeleton rig to the 3D mesh of the model. This way, when a joint is moved or rotated, the mesh will follow. Skinning also includes weight painting, a key step once the rigging process ends. Weight painting takes care of the deformation of the mesh when performing particular motions. For example, when raising the shoulder of the model, the mesh might deform in an unnatural way. Weight painting controls how the individual vertexes of the mesh are affected by certain movements of the bones, thus creating convincing deformations.

 References:

 Pluralsight, 2014. Key 3D Rigging Terms to Get You Moving. [online] Available at: <https://www.pluralsight.com/blog/film-games/key-rigging-terms-get-moving> [Accessed 8 Nov. 2018].

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