Hello All,

I have a couple HDAs inside Unity which create geometry based on a curve input (essentially extrusions of the curve). Everything seems to work just fine upon initial creation, however once the Unity file is saved, closed, and reopened, some of the curves seem to ‘break’. By break I mean that they no longer have the Houdini Engine components (Houdini Parms, Houdini Curve, Mesh Renderer). The curves no longer function as Houdini curves and in most cases the geometry that was generated from them (in another HDA) is no longer generated. The curves that break also now come in as unclosed and without the Houdini Parms component I can't close the curve. The broken curves appear as black lines instead of highlighted green as they were before.

In the attatched image you can see one of the ‘broken’ curves in black and the console errors I am receiving.

Any help or insight is much appreciate!

Thanks,
-Mat

Follow up:

After saving, closing, and re-opening, the HDAs that the now broken curves were input into also lose their Houdini components. The geometry they generated is still visible in the state I left it before closing, but they essentially become a static mesh since there are no parameters associated with them anymore. This is essentially breaking the entire Houdini/Engine/Unity pipeline and making me think I might not be able to use Houdini Engine after all

I receive the error message “Status string getter failed. Likely the session is invalid.”

Please help!

For anyone interested or experiencing a similar issue:

It seems that if I put each HDA into an empty game object before saving and closing, nothing breaks upon reopening. I haven't tested yet if I can put all HDAs into a single Empty game object but for now, each HDA in its own empty game object seems to work.

Will be creating a script to automatically wrap all HDAs, not ideal, but it'll work for now i guess.

This seems like a bug. You should report it to support@sidefx.com with your screenshots and example asset for proper tracking/resolution.

That said, when you see things like “…Likely the session is invalid.”, it likely means that the Houdini Engine process has crashed - which means Houdini has crashed running your asset.

One way to debug this is to try to reproduce it in Houdini:
1. Install the latest Unity plugin with Houdini (say, 15.0.411).
2. (re)create the scene in Unity that you think will crash next time you load the level.
3. Go to Houdini Engine > Debug > Save Houdini Scene
4. Load up the scene in Houdini.

Also, Houdini's components are still on your objects. They just don't get any GUI because they rely on Houdini Engine actually being alive.

Damian,

Thanks so much for the response! I'll definitely file a bug report with support. Should I send the Unity project, as thats where the issue seems to manifest, or the resulting .hip file? I've done some stress testing but really cant seem to find the root of the problem. It seems to only occur when I have 20+ hdas (houdini curves included), saved and closed, reopened, change some parms and move some curve points, saved and closed again, then boom, Engine dies the next time I open.

Will take the steps you suggested to troubleshoot on my own however.

Thanks so much for the response, I really appreciate it!

The more you send, the better chance we have to reproduce the issue and then fix it. Please also try tomorrow's build, 15.0.412, if you're using PolyExtrude in your assets. We just fixed a crash in there.

For the Unity scene, if you can .unitypackage everything needed to recreate the scene as well as the scene file itselfs, that would be best. Please do not include any Houdini folders when you Export the .unitypackage. Thanks!

Will do! I am using polyExtrude, so I will definitely check out tomorrow's build.

Thanks Damian!

Any progress on this issue? It still appears to unfixed. It takes away all advantage of using Houdini at all, given how unreliable it is.

What's the latest version of Houdini you've tried? Did you make sure to update your Unity project with the latest Houdini Engine plugin?

damian
What's the latest version of Houdini you've tried? Did you make sure to update your Unity project with the latest Houdini Engine plugin?

Yeah using the latest of everything (15.5.323) at the time of writing.

Try today's build (15.5.564). You'll need to redo your curves (if broken) and resave the scene.

damian
Try today's build (15.5.564). You'll need to redo your curves (if broken) and resave the scene.

Nice! It's great to see support for the Unity integration continuing. There is so much this great tool can do for game developers. I will try it tonight

Yeah that appears to be working much better (using 565 with Unity plugin from github).

Many Thanks,
-A