2019 Houdini Gallery Reel
https://vimeo.com/348882771
Lecture 02
“Hello Houdini”
CS348C-23W CG: Animation & Simulation
Prof. Doug James
Last class: What could go wrong? 😭😭
Announcements
• Install Houdini Apprentice
• Fill out pre-course survey: https://bit.ly/2Fpo5vt
• Start Homework #1
• Think about what you’d like to model over the next
two weeks, e.g., for HW2 Procedural Modeling
Homework #1:
Hello Houdini [1 week, 10%, ]
• Learn some Houdini!
• Start reading and watching videos
• Make something simple
• Submit Wednesday for Thursday “Weeklies”
• Canvas: Video (or image) + Houdini file
• Dropbox: Video (or image)
https://www.sidefx.com/learn/getting_started
https://www.sidefx.com/tutorials/houdini-foundations-book
Let’s model things in Houdini
Focus on geometry tools for now--ignore physics.
Model then screenshot.
https://www.dropbox.com/s/ts2aqvi8khkp8pn/HelloHoudini-
2023.hipnc?dl=0
Task #0: Check out workspace
Check out:
• Houdini Workspace
• Shelf tools vs “Tab Menu”
• Nodes & Networks
• Display Options (d)
• Geometry Spreadsheet
• Viewing (ESC, spacebar)
Task #1: Model a subdivision surface
Stuff to explore:
• Create a Geometry node and “dive
in” (“u” : Jump Up)
• Create a Box
• PolyExtrude then Subdivide
• PolyReduce to simplify
Check out:
• Houdini Workspace
• Shelf tools vs “Tab Menu”
• Nodes & Networks
• Display Options
• Geometry Spreadsheet
• Viewing (ESC, spacebar)
Task #2: Use HScript to animate simplification
$ Description
Things to explore: $FPS Playback speed in frames per second (as set with the Playbar
controls).
• Simple parameter expressions $FSTART Frame number of the first frame of animation (as set with the
• Avoids VEX/VOP nodes Playbar controls). $NFRAMES (the number of frames in the
animation) = $FEND - $FSTART + 1.
• E.g., Simplification $FEND Frame number of the last frame of animation (as set with the
Playbar controls).
$F The current frame, (as set with the Playbar controls). This is a very
useful variable, especially for rendered picture filename numbering.
$FF Floating point frame number.
$NFRAMES Number of frames in the animation. $NFRAMES = $FEND -
$FSTART + 1.
$T Current time in seconds. Equals ($F-1)/$FPS
$TLENGTH Total length of animation in seconds.
$TSTART Start time of animation in seconds.
BTW: Please turn on AutoSave!
Things to explore:
• “Edit > Auto Save”
PS: If it does crash, look for a crash
file in your root ($HIP) directory.
Task #3: Model a huge table
Things to explore:
• Box
• PolyBevel
• Taper
• “Copy and Transform”
• Subdivide / Polyreduce
• Merge
• Color
• “Copy parameter” & “Paste
relative reference”
Task #3: Keyframe: Animate a bunny hop
Things to explore:
• File
• Transforms
• Parent
• Box
• “Transform” node
• Keyframes
• Add Keyframe: “alt LMB”
• Del Keyframe: "ctrl LMB"
• Animation Editor: “shift LMB”
• Can keyframe pretty much anything (!)
• Make a Flipbook and export frames
Task #4: Copying: Create a spiky ball or virus
Things to explore:
• Sphere (mesh)
• Copy to Points (or Copy Stamp)
• Merge
• Watch orientation
Task #5: CSG: Create a metal screen with holes
Things to explore:
• Booleans
• Constructive Solid Geometry
(CSG)
• Subtract, Union or Intersect
• Parameter references
Task #6: Groups: Model a Chessboard
Things to explore:
• Explore Groups
• Explore “Group Expression” SOP
Task #7: Understand Attributes
Things to explore:
• Attribute types
• Point, Vertex, Primitive, Detail
• Attribute Transfer
• Attribute Blur
• Attribute Randomize
• Attribute Noise
• …
• Recall: Geometry Spreadsheet
Task #8: Wrangle some attributes
Things to explore:
• Attribute Wrangle
• Runs over points, vertices, primitives, or
detail (only once) ...
• Important attributes have names, e.g.,
• @P : Position
• @N : Normal
• @Cd : Diffuse color
• Indexing: @ptnum, @primnum
• Uses VEX scripting language
• https://www.sidefx.com/docs/houdini/vex
• Python nodes also available
• https://www.sidefx.com/docs/houdini/hom
Task #10: Iteration: Model the Cantor Set
Things to explore:
• Grid
• Scaled copies
• For-Each loop
Task #11: Implicits: Color some isosurfaces
Things to explore:
• Conversion
• (points,mesh) volume
• VDB tools
• Color isosurfaces
Task 12: Measure: Find largest isosurface
Things to explore:
• Measure (area)
• Attribute Promote (for total area)
• Visualize
• Group Expression
Up next: VEX code and VOPs
• Finer control using code
(VEX) and visual expressions
• http://www.sidefx.com/docs
/houdini/vex
• You can also write Python
code if you want ;)
A VOP shader network
Homework #1:
Hello Houdini [1 week, 10%, ]
• Learn some Houdini!
• Make something
• Submit Wednesday for Thursday “Weeklies”
