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

Chip Collier photex at gmail.com
Fri Feb 9 07:24:17 EST 2007


It's been a little while since I worked with Ogre and I used XSI for the
project but in so far as how Ogre handles data like geometry and animation I
think Houdini would be very awesome for export to Ogre.
For my project the animation didn't depend on the number of frames (unless
things have totally changed in Ogre by now this should still be the case).
You could animate what you needed and the engine would handle
timing/retiming playback speed and global influence. Only catch was that you
basically animated each major section of the character or object seperatley,
which I don't think is unusual for any engine. From there I used lua scripts
to control the parameters for each animation segment.
So in Houdini for this I'd have a series of "saved" cycles from say frames
0-100 or whatever you decide to use, these could be in a container of some
sort and the ROP could know how to get the data it needs (ie, point it to a
manager and have it export all CHOPS with the export flag on or something).
The name of each channel should obviously be coordinated here so that the
ROP can make sense of what each is to do.  From there I'm too fuzzy to go
into any details but from a usubility point of view this is what I imagine.
In Ogre are blendshapes handled by deltas or completely seperate instance of
geometry that get "blended" in the engine? I'm under the impression that
they are seperate instances of geometry which was why I never used it for my
project. This was 3 years ago though and I could be uninformed. :)

_chip


On 2/9/07, Darran Edmundson <darran at edmstudio.com> wrote:
>
>
> 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?
>
> Cheers,
> Darran.
>
> 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
> http://www.edmstudio.com
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