[Sidefx-houdini-list] Houdini Apprentice to UDK

Craig Hoffman craigleehoffman at aol.com
Wed Jan 9 21:36:13 EST 2013

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.  :)

Craig Hoffman
Technical Art Director
Good Science Studio
Microsoft Studios

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