Deborah R. Fowler
RBD | Bullet
Rigid Body Dynamics (RBD) are one of many simulations you can use in Houdini. To help guide the user I have categorized my RBD information into two sections related to the courses I teach.
- RBD Introduction — includes an overview of the solver, RBD Instanced Objects node and using the RBD for layout for example (which includes a video on RBD for layout including simming to points and using transform pieces)
- RBD Advanced (password required) — covers microsolvers, customized fractures and customized constraints
SCALE / CACHING / PHYSICAL ATTRIBUTES / BULLET ASSUMPTIONS all matter
Key Reminders
Scale & Physics
- Scale matters in dynamics — Houdini measures in meters/kg/seconds; 1 unit is a meter (about 3 feet)
- Physical attributes of your RBD objects, including your collision objects, greatly influence the simulation
- Proxy geometry can be very useful in speeding up your sim times
Caching & Rendering
- When rendering on the renderfarm, cache — see also the SideFX caching documentation
Do not render your DOP network! Always bring the information out from your sim with a dop import
(or if your dopnet is in SOP level you can also use the Object Merge tab)
Bullet Solver Notes
- Bullet was developed to be fast based on assuming things are convex, but there are ways around this
- Note: In H16 the RBD Static Object has moved to the Collisions tab
- Note: In H18 the RBD Bullet node in SOPs has been added for convenience — the RBDbulletsolver is packaged for convenience and it is important to be aware of both
Further Reading
What's New
- New in H20
Sticky collisions, curved glass
- New in H18
Guided simulations (low res to high res or animation); RBD Bullet Solver now works at SOP level. Examples found under RBD Bullet Solver/Examples — look for GuidedRBDBulletSolver.
- SideFX guided RBD example file
- New tools in H17.5 — Fuat Yuksel's summary, MucHUG April 2019
Presets for fracture via rbdmaterialfracture node (concrete, glass, wood); RBD constraints and Vellum Tetrahedral Fiber Constraints
- RBD features update in H17 by Cameron White
Tutorials & Masterclasses
- Steven Knipping's Applied Houdini RBD I (free)
Packed, transforms, Voronoi, boolean, tools
- Bullet Solver Masterclass (H12)
- H13 Masterclass — Bullet Solver with Cameron White
Documentation & Reference
- SideFX Dynamics documentation
Be sure to include reading the "top ten" lists (see Subtopics/Learning Dynamics near the bottom of the page) that link to further pages.
- bulletphysics.org
- fxguide: Art of Destruction