Hi, I'm trying to create fractured meshes for dynamic destruction in UE4. When I select my mesh and hit the “Static Fracture Export” shelf button, I get the static fracture export sop attached below my mesh, as expected. When I hit the “Create Container” button, though, I get an error:

“Error Running Callback:
Traceback (most recent call last):
File ”<stdin>“, line 1, in <module>
File ”opdef:gamedev:op/sop_static_fracture_export?PythonModule“, line 12, in generateGeometry
File ”CPROGRA~1/SIDEEFF~1/HOUDIN~1.633/houdini/python2.7libs\hou.py“, line 38825, in attribValue
return _hou.Point_attribValue(*args)
OperationFailed: The attempted operation failed.”


I'm pretty new to Houdini, so I'm probably doing something wrong. Is this the kind of error I'd get if I haven't installed the tools properly? Or, maybe I'm just using it incorrectly? If anyone can help me get this working, I'd really appreciate it!

Side note- I notice a ton of new Game Dev Tools listed for 16.5. I assume I have to have Houdini 16.5 in order to use those, correct?

Thanks!
Brian

OK, I got the tool working on one very simple test with a fractured box. However, I tried again on my fractured geometry, and I got the same error as before. I then created a new file and tried it on a simple fractured sphere, and again got the error.

When I get this error, the tool still creates a “FRACTURE_CONTAINER” node in the obj context, but there is not geometry in it.

Are there special requirements for how the geometry needs to be set up? I can't tell what was different in the one version I got working.

Hi,

Sorry to hear you are having problems with this particular tool.
This is a tool we have not touched in a rather long time, so it needs some cleanup to make it more robust.

The current tool expects packed primitives to be fed into the input. It will then generate one geometry container inside the “FRACTURE_CONTAINER” per piece. So make sure you only have packed geo, and no other types.

I will be improving the tool today, so expect a fix on Github either today or tomorrow

Paul

Thanks for the info, Paul! I really appreciate it! Packing the geometry with an assemble sop did indeed allow me to export the pieces using the Static Fracture Export, and I was able to import it to Unreal. The orientation was not correct, though, and I did try setting the Transform Order on the FRACTURE_CONTAINER to Rx Rz Ry. Is there a way to fix that?

Side question- if I fracture a mesh, do you know a way to group some of the chunks so Unreal acts as if they were one pieces? Sorry if these are rookie questions!

Thanks again!
Brian

Hey Brian,

The orientation should be correct. Have you changed your import settings in ue4 possibly?

To your second point - ue4 does provide the ability to group chunks by creating a physics object and creating different levels but as far as I know the only way to author those levels currently is through the nvidia physx lab tool.

Mike

Thanks, Mike, turning on “Convert Scene” in the fbx import dialogue seems to have fixed it. I had thought that was on, but I guess it wasn't.

I will have to mess with the PhysX tool and see what I can get working.

Hi Brian,

Just wanted to let you know the revised version of the Static Fracture Export tool is now live in the Development branch on Github. (Meaning you can manually download it, or wait until we include it in the automated download system)

I will also create a tutorial video explaining what the tool is used for, including some information about the new parameters it features.

Paul

Awesome, Paul! Thank you! Where will I find the tutorial when it comes out?

You will be able to find it on the SideFX Tutorials page!

https://www.sidefx.com/tutorials/ [www.sidefx.com]

Paul

Thanks, Paul!

With your changes, I was able to get my object imported as a Dynamic Fracture Mesh in UE4. Materials and normals seem to be working correctly. The mesh still came in rotated 90 degrees on the X axis, but I think that has something to do with the odd way you have to import dynamic meshes. I worked around it by rotating the mesh in the opposite direction before exporting.

Hey Brian,

Happy it solved your problem! As for the rotation, the default UE FBX importer has an checkbox called “Convert Scene” which will take care of that. But since you're not using that, it might skip that conversion step and not adjust the coordinate system. This HEngine page describes what happens: http://www.sidefx.com/docs/unreal/_coordinate_system.html [www.sidefx.com]

I know you're using FBX to do File I/O instead of HEngine, but it at least shows you how to fix it.

Paul