[Sidefx-houdini-list] real-time animation and workflow conventions ...

Darran Edmundson darran at edmstudio.com
Fri Feb 9 00:37:23 EST 2007

We've got a developer working on a custom ROP for exporting to the 
popular Ogre scene-graph engine (www.ogre3d.org).  He's very good, and 
is consequently making short work of our initial wish-list.  This puts 
us in the wonderful position of being able to accomplish more than we'd 
originally envisioned.

For anyone interested in (or already) using Houdini as an authoring tool 
for game content, how would you handle:

1) Animation Cycles.  Many engines support loading and playback of named 
cycles.  E.g., an initial robot->setAnimation("walk") followed by a 
per-frame update robot->setTime(framenum*dt).  How would you keyframe 
and encode this info into a single HIP?  Options I can think off:
    - create a digital asset, drop an instance of the character/object
      and treat each instance as a separate cycle (to be pulled together
      by the ROP).
    - Use one object and break the various cycles up into different
      frame ranges.  You'd then have to indicate this to the ROP, e.g.,
      walk: 0-100, jump: 101-160, etc.
    - alternatives?

2) Morph Targets.  Many engines support morphing between different 
(topologically equivalent) named targets.  The ROP needs to enumerate 
the possible targets.  Houdini's BlendShapes SOP would seem to be 
natural way of encoding these states.  For example, the ROP could look 
to see if the display flag on an object is a BlendShape SOP.  In which 
case, it should store the various input geometries as the morph targets.

With this and other types of animation, you can see the need then to 
settle on workflow conventions.  What conventions are you using to 
facilitate export to a game engine?


P.S. One day soon, Collada will hopefully make all of this moot.  With a 
deadline in April though, we can't afford to wait.

Darran Edmundson [darran at edmstudio.com]
Interactive visualization for museums and industry

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