Mesh split question

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I have been working with the Houdini Engine for a couple weeks now and I havent found the correct way to actually split meshes.

What would be the correct way to split meshes so I end up with 2 or more static meshes in Unreal? I managed to do it with a simple cube and a sphere by making the sphere a primitive. But that wont work for generated geometry.

thanks in advance!
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Hello!

In Unreal, we split everything by geo/sop. In terms of Houdini Engine, for each object/geo/part one Unreal static mesh will be created.

You can also use rendered_collision_geo (rendered_collision_geo0, rendered_collision_geofoo, etc) prefix to mark groups for further splitting. For each sub group within object/geo/part additional splits will occur.

Hope this helps!
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I'm having trouble getting the collision geo to work correctly. I am using copy stamping to produce the two versions of my mesh, the rendered mesh and the simpler, convex collision mesh. I'm also using the Copy groups option to create a separate group for each. Then with group nodes I am renaming the copy groups to “main_geo” and “collision_geo1”.

But when I import this .hda to my unreal project and bake it out, I get two separate static meshes instead of the one static mesh with collision.

What am I doing wrong? I have one geo node at the /obj level, and inside is a subnet convereted to a HDA, and the nodes are all in the subnet.
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Hello Mike!

That's the correct behavior right now. For each unique collision_geo group it will create a static mesh, assign it to be collidable and make it invisible. For each rendered_collision_geo it will create a static mesh, assign it to be collidable and keep it visible. In your case, following these rules, it will create two meshes (everything that is in collision_geo1 and everything that's not in collision_geo1). Can you use rendered_collision_geo group for your case?
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Ok, I see that the static mesh I specify in the collision_geo1 group is set to use complex collision as default, and the main_geo group static mesh uses default collision. But my collision_geo static mesh is visible. So it's not really any different than rendered_collision_geo.

Are there plans to support UE4's native static mesh collision system? Like creating UCX_ or UBX_ groups?
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Yeah, I would second this. Why break convention here?
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Hello!

If collision_geo is visible then it is a bug, could you please file it and attach a sample asset?

We do, indeed, use complex collision as default for collision and rendered collision geos at the moment. Yes! We are looking at adding UCX/UBX support. Right now the functionality is on par with Unity one in this regard.

We are also looking at adding bounding primitives support to Houdini Engine in the future, which would simplify creation of UCX/UBX.

Thanks!
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Hello!

If collision_geo is visible then it is a bug, could you please file it and attach a sample asset?

We do, indeed, use complex collision as default for collision and rendered collision geos at the moment. Yes! We are looking at adding UCX/UBX support. Right now the functionality is on par with Unity one in this regard.

We are also looking at adding bounding primitives support to Houdini Engine in the future, which would simplify creation of UCX/UBX.

Thanks!

Sure, I can do that. Would you like me to attach the .hda file or the .hip? I'll do a bit more testing on my end just to make sure it truly is a bug first though. I wonder if it might have to do with using the pre-compiled .DLL instead of building from source?

Bounding primitive creation support in Houdini would be awesome! Will it automatically deal with concave meshes and split them up into multiple convex hulls? UE4 already has a feature to do that but I've been terribly disappointed by the quality of the the hulls it produces. Not optimal at all. For most concave objects I end up manually creating the convex hulls.
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HDA should be fine No, it is most likely a bug.

Well the idea is that it would let us tell what type of the bounding object is, sphere, cube etc and from that we'd be able to generate corresponding host bounding volume.

I was thinking maybe in the meantime we can add support for detecting these via specialized group names. For example for UBX, you could flag geo with collision_ubx prefix? Then UE4 plugin would detect that and produce box collider.. Would that be helpful?

Yes, I have the same experience when generating complex hulls in UE4. I think in most cases you would probably end up manually creating them.
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I was thinking maybe in the meantime we can add support for detecting these via specialized group names. For example for UBX, you could flag geo with collision_ubx prefix? Then UE4 plugin would detect that and produce box collider.. Would that be helpful?


Yea, sure, I think that sounds just fine.
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Hello; I am following up on this thread. We've logged RFE support for simple collision primitives inside Houdini Engine in RFE #61716 . Similarly, we've scheduled UE4 work for UBX/UCX support.

Does the geometry split issue still occur for you?
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