Procedural Animation Lecture 2: 3D & Houdini basics 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 World space vs. object space Order of transformation Houdini nuts and bolts

World space & object space Each 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 called 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 (translation, rotation, and scaling) are applied to an object. Changing the order of transformation yield different results. Demo in Houdini

Order of transformation Demo in Houdini

Houdini nuts and bolts Houdini contexts Linking panes in a desktop Moving custom desktops Locking view to a camera Saving animation frames Creating an animation file Hotkey quick reference Maya transition guide

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

Linking panes in desktop 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.

Moving custom desktops You can move your custom desktops to another machine by copying the .desk file in Drive :/Users/netid/Documents/houdinixx/desktop/

Locking view to a camera In a View pane, you can keep looking through your camera by turning on Tie View to Camera/Light option in the popup menu that shows up by clicking here or by turning on Lock View/Light to View by clicking here

Saving animation frames Open Floating File Choose, select a folder and set a file name (e.g., tutorial_chap1_test1.$F4.pic) Override Camera Resolution lets you scale the frame size.

Creating an animation file In Houdini’s main menu (top left), chose Render -> MPlay -> Load Disc Files... In Load Image, select animation frames as an image sequence. In MPlay, chose File -> Export -> Video for Windows 64.bit. Above turns .pic files (animation frames) 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.