Chapter 4 - Animation Basics Continued

This is a continuation blog post from the last one, I will now share the rest of my notes I took from this chapter on Animation basics. On the previous post, there was a section of ways to scale animations, and one of those ways of scaling was using a Dope Sheet.

4.5 Dope Sheet Editing

Also known as an Exposure Sheet, it's a chart that is used to organizes the information within your animation. It shows the list of frames running vertically with a number of columns running across the page horizontally. These columns contain different information about your animation - things about notations about dialogue or camera change, or special effects.

In 3D, dope sheets list frames in a horizontal direction consistent with the timeline, basic dope sheet function is to offset key frames - so moving the key frame on the timeline left or right will effectively change the timings for that portion of the animation.

4.6 Forward Kinematics

The definition of Kinematics means the study or calculation of movement. When models are complex than a simple one-piece, people would organize the parts in a hierarchy in order to have more control over the elements of different transformations applied to the model. Animating within an hierarchically organized structure is known as hierarchical animation - this is also known as forward kinematics. 

Forward Kinematics (FK) calculates the animated transformations of each node of your hierarchy. The forward direction down the tree of the hierarchy - parent to child.

4.7 Inverse Kinematics

This works in the polar opposite of FK, the positioning of the child joint will effectively determine the position of the parent joints within the model - meaning in this instance, the child becomes the parent and the parent becomes the child. While kinematics is the study of motion, inverse (in this sense) refers to the flow of transformations within a hierarchy in the opposite direction. IK models are used quite frequently in humans and animals.

Human and animal joints have limits - which means the joints can only bend so far, because of this, it is common for 3D Animation Systems to impose 180-degree-rotation limit of joints in an IK model. This restriction might pose a problem when you want to bend of a limb to change direction. 

Normal Hierarchical Groupings: one arm, one leg, so on. For human models:
- one skeleton for each leg
- one skeleton for each arm
- a separate skeleton for each flexible backbone
- final skeleton for the head and neck
The Pelvis would become the parent of the entire hierarchy for a biped character.

It's always important to define the structure of your skeleton, in a way that allows you to make the movements within your model. It's also very important to to have an understanding of how the joints move in your model, for human characters - you can easily use yourself or a friend to reference how joints move.

4.8 Motion paths

There are two broad approaches to animating objects through space.
1. A motion path is when an objects moves along a path using a standard curve drawing tool, you can also change the path using curve editing tools.
2. A timing curve represents the rate of movement along the path, it plots on one axis and the percentage of distance on the path along the other axis.

This concludes the notes I have taken from this chapter. A very interesting read, considering I had only scratched the surface of 3D Animation. It was enlightening reading about the two different kinds of kinematics - I do understand that in Maya you can put IK handles at different parts within the hierarchy so I can now start to think about what parts of the model will use what kind of kinematics. It was also good to read on the different kinds of interpolation - it also means that I can experiment with how each different type will affect my animation for the better or not.