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Terrain .hda Unreal to Houdini

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Hi! It's my first work with Houdini Engine to Unreal. I created a terrain in Houdini, saved digital asset .hda and I imported it into UE4. Now, I wold like to know if I can save the changes made on Landscape in Unreal (ex. sculpt, Landscape spline for road...) in the .hda file and review them in Houdini. If it's possible, someone can help me to understand how I can do it?


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Welcome to the forum Mary.

You could save the change out to disk with a rop_geometry or equivalent, this is the simplest.

Another way that may be preferable is to use the Houdini Engine Debugger in Houdini. This will make Houdini do what ever Unreal is doing with Houdini Engine.



In Houdini go to the Windows > Houdini Engine Debugger. Find out what port Unreal is using through the unreal houdini engine interface it should be the defaults, I don't have unreal at my desk to check at the moment. And press start. 




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I believe the Houdini Engine Debugger is what your after. Once the Houdini Engine Debugger has been started on the correct port, any changes you do in Unreal should real-time reflect in Houdini. For an example say you have a simple .hda that is a grid with a mountain sop to maker a rudimentary terrain. As you adjust the .hda in Unreal changing say the amplitude of the noise, it would reflect those changes like a ghost was editing it in Houdini. 

Encase the issues is otherwise, there is also the bake option on the HDA in Unreal. Maybe you are just looking for that? Where once you change the settings on the HDA is makes the copy of the content preserved in unreal. Unfortunately by default the Houdini Engine will not save preferences for session to session. The only work around would be to make your own preset system in python for the .hda to save your parameter settings you have changed and then load them again in your next session.

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I write you steps I've done. 

I created a .hip file and its digital asset .hda.

 in windows-> Houdini engine Debugger I tried to start debugger both as TCP Port as Named Pipe;
- I esported digital asset .hda from Houdini to Unreal
- In Unreal I went to Edit -> Project Settings -> Plugins -> Houdini engine -> session and I tried to start the “session type” both as “TCP Socket as Named Pipe or domain socket” on port 9090;

Now I can't see the changes between file .hip open in Houdini and file with changes made in Unreal. Did I forget a few passes?

if I can later I'll attach a video.

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That is so weird... If the pipe were working correctly the hda node should just get created in the Houdini session, which to your point it clearly does not.

The only thing I think I could suggest is to open Unreal first, i.e. have Houdini closed. Switch the Session Type to Named process, so the value is hapi, as opposed to TCP as that specific port may be used by something else in your system, you could test this by trying another port number too if you wanted. Toggle the start of the automatic server... And then open Houdini, turn on the Houdini Debugger go to Named Pipes and then press start. Muscle memory as best as I can repeat it. I think you may be starting the debugger prior to when unreal would be available to be listened too.

Another thing to check is, is your HDA available in your houdini session already? Like can you see it available in the tab menu in the objects or the sops context? I don't think this would be the case, but it could just not have it in it's otl search paths i.e. in your $HOME, $HOUDINI_PATH $HOUDINI_OTL_SCAN_PATH ?sp?

Otherwise I would ping support at sidefx.com and give them your system info and all the above with your issue. It's possibly a bug, or in all case I'm missing something. It's one of those things at this point for me I would need to sit down at the desk and let my muscle memory do the work. I type more keys than I think about most times. 

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