The result of an HDA as the input for another HDA?

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Hi!

I'm trying to make a building generator (I'm probably the first to try this...). If I didn't use Unreal, I would simply have my first HDA output the hires main parts of the building and also (output #2) the simplified, box version that could conect to another HDA for the creation of stairs/ladders/balconies/etc. It would basically be a chain of HDAs, each adding an element to the building.

This method is easy in Houdini, but in Unreal, is it possible that:
A) an HDA would have 2 geo ouputs (hires and lowres)
B) use that lowres as an input for another HDA?

If I can't do that, it means I would have to make one uber/super HDA containing absolutely all the building elements. I'd like to avoid that workflow.

-Olivier
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... so, there's no way that an HDA ouputs a geo that would be the input for another HDA?

For example, I'd have an HDA that creates a star shaped geo and another HDA that would scatter tiny cubes on the star?
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Hi,

You can use "Asset inputs" for that.
Assuming you have two HDAs in Unreal, you can set the "tiny_cube_scatterer" HDA to Asset input, and select the "Star" HDA.

This will effectively connects the two HDAs directly in Houdini, unlike for example, using a World input, which would send the unreal output of one HDA to the other.

See:
https://www.sidefx.com/docs/unreal/_inputs.html#InputsAsset [www.sidefx.com]

The one caveat to that, is that you cant select which output of the HDA is connect to your second HDA's input.
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Ah, ok, I just found out each time I rebuild my first HDA (Star geo), it saves a copy of the geo in content browser: HoudiniEngine - Temp - StarGenerator. So, I can click-and-drag that geo into my second HDA as an input.

EDIT: Oh, I saw your post after I wrote this one. Can you give me more info about "set the "tiny_cube_scatterer" HDA to Asset input," ? Not sure I follow.
Edited by olivierth - July 4, 2022 17:00:14
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I see a tab for Houdini Outputs but I don't see one for Inputs...
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AHHH!! This is sick! Thanks a lot! Here's an image to show how this works (for anyone else). In my second HDA (scatter_on_Geo), I scroll down to the Houdini Parameters. I changed the the "Geometry Input" (is like that by default) to Asset Input. Below that, you'll see a list where you can pick another HDA as the input. That way, any time I modify HDA01, HDA02 updates automatically!

Attachments:
HDA_affecting_other_HDAs.JPG (229.8 KB)

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