Environmental Animation - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 359

Chapter 13
Environmental Animation
This Is Not a Physics Class
We've done some math, and now we're going to do some physics. For certain tricks in animation, there
is no substitute for the real thing. A bunch of tumbling blocks. A flag blowing in the wind. A shirt draped
across a moving body. You could hand-animate each of these, but they are so familiar to us that even a
small deviation from real motion will ruin the illusion. In such cases, it can be helpful to use a physics
simulation. Blender includes a number of simulators: rigid body (hard objects), soft body (squishy things),
cloth, smoke, and fluid. Unfortunately, Blender's rigid body system was not available before the publication
of this topic. Lucky for you, you can ind a whole section about the rigid body simulator in the Web
Bucket for this chapter as soon as the developers have it hammered out.
Cloth and Force Fields
While it would have been great to add a cloth simulation to our character's shirt, Blender's version of
cloth just isn't up to the task yet. Flowing skirts, banners, and flags all work great, but the kind of pinch-
ing and friction-based wrinkling that occurs in a fitted item like a shirt makes using the simulator next to
impossible for it. Let's take a look at what it can do though, by adding a simple set of curtains to our
example scene's window, then lightly disturbing them with some wind.
Okay, for the home décor people, these aren't technically going to be curtains. They're shears. Curtains
require massive amounts of wind to move and block way too much light. Shears can be disturbed by the
slightest rustle and are mostly translucent. The model is simple: a Grid mesh primitive, subdivided once then
scaled down along the z axis. To make it fancy, I've selected every other column of vertices and moved
them a bit backward, creating the zigzag base you see in Figure 13.1 . The shears will be attached to some
kind of curtain rod at the top, as they are in real life. This kind of fastening is indicated in the cloth simulator
by an option called Pinning , which protects vertices from being affected by the simulation and causes them
to act as anchors. I've selected the top two rows of vertices and made them into a vertex group called
“pinned.” The material settings aren't important to the simulation, but if you're curious, they use Translu-
cency, the Minnaert shader, and Z-Transparency with Fresnel. If you're following along and adding this to