ATEC 3316.001 Procedural Animation Introduction to Procedural Methods in 3D Computer Animation Dr. Midori Kitagawa

In class Pay attention Take notes Learn Be ready for a pop quiz

Lecture 2: 3D animation foundations What is procedural animation? -- Three types of 3D computer animation World space vs. object space Order of transformation Pivot Houdini

What is procedural animation? Three types of 3D computer animation Keyframe animation Motion capture animation Procedural animation

Keyframe animation Read Kerlow Section 11.1

Keyframe animation Keyframe is a drawing of a key moment in an animated sequence, where the motion is at its extreme. Inbetweens fill the gaps between keyframes. Every motion is created by animators. Read Kerlow Section 11.1

Keyframe animation To produce keyframe animation, the animator builds the behavior of a 3D model by keying parameter values in frames where the values are at their extremes. Read Kerlow Section 11.1

Keyframe animation Based on traditional hand-drawn 2D keyframe animation method. Animation is manually produced from scratch. Examples: Pixar and Blue Sky animations Read Kerlow Section 11.1

Motion capture animation Read Kerlow Section 12.2

Motion capture animation To produce a motion capture animation, the motion of a capture subject is recorded as 3D data and applied to a 3D model. The animation is produced from the capture subject’s movement. Read Kerlow Section 12.2

Motion capture animation Although no 3D data is involved in rotoscoping, motion capture technology is sometimes referred as “devil’s rotoscoping.” Examples: CGI characters in live action films, 3D animations and games Read Kerlow Section 12.2

Procedural animation

Procedural animation To produce a procedural animation, the animator defines a procedure or a set of operations to be performed. Each operation can generate or alter data that passes through it and can be conditionally or non-conditionally executed.

Procedural animation With some procedural methods (e.g., particle systems, rigid dynamics and flexible dynamics), the user specifies a set of rules, initial conditions and parameter values and runs simulations. Physics-based animation is a subset of procedural animation http://work.gmunk.com/TRON-Fireworks

Procedural animation Procedural methods can be used in any part of production pipeline to produce geometries, textures, lights, rigs, animation, composites, sounds and other elements. Examples: visual effects (e.g., smokes, steam, fire, clouds, dust and water) in live action films and 2D/3D animations.

World space & object space Scene is built with an arbitrary number of objects, lights and cameras in the world space, which is also called the world coordinate system or global coordinate system. Each object is generated in its object space, which is also called an object coordinate system or local coordinate system.

World space & object space in Houdini World space is cal led the scene level or object level. Object space is called the geometry level or SOP level.

Houdini: Scene level and geometric container objects Geometry container object is often simply called “object.” Objects, cameras and lights define a scene in the scene level.

Houdini: Geometry level and surface nodes Surface nodes are also called Surface Operators or SOPs. SOPs in the geometry level define the geometry inside the geometric container object.

World space & object space Object space and world space work together. For instance, if the geometric center of an object is at the origin of its object space and if the object is placed at the origin of the world space, it will be centered at origin of the world space. However, if the geometric center of an object is not centered at the origin of its object space, it will be off-centered in the world space even if it’s placed at the origin of the world space. Demo in Houdini

Global transformation vs. local transformation Transforming an object in the scene level is considered as global transformation animation. Transforming a geometry in the geometry level is considered as local transformation or deformation.

Order of transformation Specifies in what order transformations are applied to an object. Changing the order of transformation yield different results. Demo in Houdini

Pivot Transformation origin Pivot is at the origin of local space by default. Pivot can be moved. Demo in Houdini

Week 1: Houdini stuff Houdini contexts Linking panes Hotkey quick reference Maya transition guide File organization

Houdini contexts Major parts of Houdini (contexts) and corresponding node networks: /ch CHOP (channel operators) network /img COP (composite operators) network /obj Objects, cameras, and lights /obj/geo SOP (surface operators) network /out ROP (render outputs) /part POP (particle operators) network /shop SHOP (shader operators) network /vex VOP (VEX operators) network

Linking panes If panes in Houdini desktop are linked by the same number, when you move to a different part of Houdini in one pane, all the other panes follow you. If panes are not linked, a big confusion can happen.

File organization and scripts Scripts to create folders from inside Houdini work on Linex and Unix (OS X) machines and help you name folders and files in a systematic manner, i.e. help you organize your project. Unfortunately these scripts do not work on Windows machines. Working in the Linex/Unix environment is highly recommended but not required for this course. No matter on which OS you are running Houdini, name folders and files systematically and organize them efficiently.

Saving animation frames If you are not using Unix/Linex, select a folder and set a file name (e.g., A1.$F4.pic) using Choose File.

Creating an animation file In Houdini’s main menu (top left), chose Render -> MPlay -> Load Disc Files... In Load Image, select animation frames. In MPlay, chose File -> Export -> Video for Windows 32.bit. Above turns .pic files into an .avi file.

Houdini reference & guide Print out Hotkey quick reference and keep in your notebook so that you can look at it whenever you need it. You may find Maya transition guide useful to understand Houdini’s contexts if you are a Maya user.