[Sidefx-houdini-list] Houdini Apprentice to UDK

Ken Ouellette ken.ouellette at gmail.com
Wed Jan 9 23:01:14 EST 2013

Having somewhat recently moved into games... I transitioned from a Feature
Animation/VFX "upbringing" to the games environment last April and now get
to work with Craig....

I was hopeful about usign the Apprentice to help learn Unreal via using it
and the UDK, but without FBX support that was quickly stopped. If the
intent is to author any animation from a DCC (maya, houdini, etc) and get
it into the UDK you need to use  skeleton and rig it and that means FBX
export. Like Craig I've been able to get an FBX from Houdini into Unreal,
but it was a bit more work. You can fiddle with the import options and do
some work to avoid the smoothing group options but  I haven't tried it for
deforming mesh. Static should be okay if you can sort out the import issues.

Unity is a bit more forgiving and has options to allow for bone scaling.
UDK/Unreal doesn't like that at all, you can do a uniform scale in its
AnimTree editor, but it only expects rotations by default. Even to get
translations in and working you have to dive down and flip a toggle. I
haven't tried to go from Houdini to Unity but it should be possible.. I'll
give that a go when I get a chance.

Unity will see the .obj and you can use it without pain. IT doesn't have
native support for blendshapes (morphs). You can write your own script to
do that or find a solution in the UnityStore or forums. Its animation
editor is great comparatively to UDK's Matinee, but it is still quirky and
your animations may actually be easier to execute in a DCC that can export
a FBX. Unity will allow you to scale joints in the DCC and it will respect
that change IF you put the imported animation to use its "legacy" mode.

I would recommend Unity and a DCC capable of spitting out reliable FBX at
the moment for animations and mesh.. it will be easier. For particles, you
as Craig says, you have to do that in-engine for that kind of work.

FWIW - if you look at Unity at a highlevel there are a lot of similarities
to Houdini....

Ken Ouellette
Technical Art Director
TUFF Studio
Microsoft Studios

On Wed, Jan 9, 2013 at 6:36 PM, Craig Hoffman <craigleehoffman at aol.com>wrote:

> Thought I would chime in here as a long time Houdini user that has been in
> the game world for a while and has UDK experience.
> Unreal only imports .fbx files now.  It has no .obj import.  Houdini
> Apprentice doesn't export .fbx- you have to have a paid Master or Escape
> copy to export .fbx.  Even with a paid version, .fbx import into Unreal is
> difficult.  I have had success in the past, but I recall a bunch of issues
> with surfaces coming in faceted, etc.  Other packages have support for
> "smoothing groups" that I believe Unreal expects or something.  Regardless,
> there is a lot of futzing with things (.fbx export and import settings,
> point vs. vert normals/Uv's, etc.) to try to get it to work properly and I
> know experienced Houdini users who gave up after constant crashing of
> Unreal during Houdini .fbx import into it.
> Unity has support for importing .obj files, and I believe Apprentice can
> export .obj files- so that would work.  But .obj is quite limited beyond
> basic static meshes with one uv set (you might have to make sure it is a
> point attribute rather than a vert attribute- I can't remember) and no
> extra attributes, though vert color should work (but I recall some issue
> with that too...).
> Anyway, if you want animation (not just static models) Houdini Apprentice
> isn't a solution- and even the paid versions are wonky as I mentioned
> earlier.  I know Side Effects wants to get more Game Companies using
> Houdini, so hopefully they are actually making some effort to make sure
> their .fbx export will easily import into the major game engines in the
> near future.
> As far as FX stuff goes- particles and such- those are generally done in
> games in the real time sprite and ribbon based particle systems that are
> part of the game engines.  Unreal has Cascade and Unity has a new higher
> quality Particle System in Unity 4.0.  There is no easy way to bake out a
> particle system from a package like Houdini or Maya and import into Unreal
> or Unity.  For real time you have to stick with sprite/ribbon type particle
> FX or skeletal meshes for other things- though blendshapes are also
> supported.  This is for performance on the GPU.
> I once took a Houdini DOPs shatter sim and attached bones to the pieces
> and exported the .fbx from Houdini and got it into Unreal in the past, but
> it wasn't easy.  It would be great if Side Effects added support for tools
> like that so that artists can easier utilize Houdini's fantastic dynamics
> stuff to bake out sims for import into game engines.
> My 2 cents.  :)
> Cheers,
> Craig Hoffman
> Technical Art Director
> Good Science Studio
> Microsoft Studios
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