Another Automation - Auto Combining Plenums

chriswmackey · October 10, 2025, 3:44pm

Actually, now that I’m looking again, I’m not sure that I am understanding what you mean by “merged into a single space” since it looks like the plenum is one space in the pollination 3D preview. Can you elaborate?

mostapha · October 10, 2025, 3:54pm

Yes. The preview is fine in the Model Editor but the issue happens in the exported GEM file. It might be a bug in the DFJSON → GEM translation. See the image below. There are 3 ceiling plenums instead of one. There is only one room as expected.

different-height.gem (4.9 KB)

chriswmackey · October 10, 2025, 7:31pm

Hey @mostapha ,

I see what you are talking about in your GEM file but I cannot recreate it in the Model editor and Revit plugin that we released. Here is a POMF that I use and the corresponding GEM export that I get:
merge_test.pomf (283.8 KB)
test_merge.gem (4.6 KB)

You can see that the plenum only occurs once in the GEM file:

If you are still experiencing this issue, then send me some more steps to recreate it on Basecamp.

mostapha · October 10, 2025, 7:40pm

@chriswmackey, try this model. The issue happens when the room in the middle has a larger plenum depth.

merge_test_2.pomf (280.1 KB)

The other model that you sent also worked for me.

chriswmackey · October 10, 2025, 7:59pm

Hey @mostapha ,

I see. I can only recreate the issue when the plenum depth of a room is set to be more than double the plenum depth of the neighboring rooms. If I just change the neighboring plenums in your example to have a depth of 1.5 feet (half of the 3-foot depth you used for the middle), everything gets merged fine. Similarly, when I only used plenum depths of 1 foot and 2 feet in my example above, everything merged ok.

Let me look at the source code to see what is happening. Maybe the bottoms of the plenums are so different that they are triggering assignment to different stories or something like that.

chriswmackey · October 11, 2025, 12:26am

Ok, here is the part of the code that is responsible for this effect:

github.com/ladybug-tools/dragonfly-core

dragonfly/building.py

master


      
          min_ciel = min(rm.floor_to_ceiling_height for rm in story.room_2ds)
          room_groups, _ = Room2D.group_by_floor_height(story.room_2ds, min_ciel)
          for rm_group in room_groups:
              Room2D.patch_missing_adjacencies(rm_group)

So removing that code will get the plenums to join for this case. But I remember why this part of the code exists. There is a common case with these plenums where I need to ensure that the adjacencies are not transferred because the Room2D floor-to-ceiling heights between rooms mean that the plenums should not be joined:

The code I have there currently prevents these type of fatal error cases from happening but it also prevents some of the useful cases from going through if the plenums differ enough in height from one another.

Give me a little time to think of a better way to identify the bad cases while keeping the good ones.

chriswmackey · October 11, 2025, 5:15pm

I pushed a fix for the problematic code and I verified that it gets this case of plenums to join well:

We just need to make a new release of the installer and test it, @rafaelhok . @mostapha can let you know once it is available.

Thanks for helping us find the bug before we made a big release announcement!

mostapha · October 11, 2025, 9:13pm

The new release is out (v2.293.3) and I can confirm that it works as expected:

@rafaelhok, just keep two items in mind:

You must now solve adjacency between the rooms for this feature to work which was not a requirement for export to GEM in the past.
You need to select the appropriate Merge Method when exporting the model.

rafaelhok · October 13, 2025, 2:14pm

I’ll get the latest installed and start playing around with it.