Lecture 8 - Review of Hiearchical Modeling

Lab 5 (HM - Hierarchical Modeling) helps practice geometric transforms (placing and building our scene, as well as animating things on objects in a compact way). You also are building all of that in Project 2, so keep that up.

Some things about the obj's:

• The file formats aren't really agreed upon by us, so you'll sometimes see fbx as a file format that you'll have to convert from.
• Some places to get obj includes:
  • Sketchfab
  • NASA

Also MT on Thursday. It's only based on the lecture exercises and quizzes.

Outline of Hiearchical Modeling

We want to move things relative to each other. The MatrixStack from Lecture 7 - Continuing Matrices#Hiearchial Animation (Geometric Transforms) helps us do that. The base code for the lab starts this by scaling, shifting, and generically transforming a sphere, and adding more parts:

The idea here is that:

• Think outside in. Build the hand, then the lower arm, then the upper arm, then the body.

Let's think about it step by step. First, we want to scale, then translate, then rotate (to make an angle), then translate to the upper arm. The following pseudocode does this:

// place on body
translate on the L5
rotate SHtheta
translate by Shoulder pivot

// just LA (lower arm)
push 
	translate(where on upper arm)
	rotate(given some angle between the arm parts)
	translate(by Elbow Joint)
	scale(2,1,1)

	drawSphere()
pop

// just UA (upper arm)
scale(4,2,2)
drawSphere()