It seems geometry files written from Houdini 16 cannot be opened using Houdini 15.5+

I am currently deving some geometry using houdini 16 because the tools I need are not available in 15. Our farm cannot be updated due to current production and so I am attempting to output the base layer of the effect as bgeo files so that I can do the simulation work and rendering in 15.

Houdini 16 can read the bgeo files just fine. However, Houdini 15.5.480 returns an error saying the files cannot be read. Bgeo.sc returns the same error. Alembic works but I'd rather not have to deal with a 2gb+ alembic monolith. My current work around is to import the alembic using 15 and unpack convert and rewrite the files to bgeo.sc that Houdini 15 can read. This just seems like a silly step, hoping there is a simpler way.

Has anyone had similar problems and/or seen any documentation about changes to the format?

Hoping this is just user error on my part >.<

Read through this thread. It explains why there can be compatibility problems with earlier versions of Houdini.


polysplit in h16 generates different point order? [sidefx.com]

The representations of certain geometry changed in Houdini 16.0. There are a couple ways to do it as evidenced by the following journal entries:

Houdini 16.0.438 The representation of polygons and tetrahedra in newly-saved geo and bgeo files has changed to improve performance. Older versions of Houdini will not be able to load these new files, so to save using the old format, set the HOUDINI15_5_GEO_COMPATIBILITY environment variable to 1 before saving the

Houdini 15.5.669 Added ability to load geo/bgeo files saved in Houdini 16.0 containing polygons or tetrahedra. To load files from Houdini 16.0 in earlier versions of Houdini 15.5, set the HOUDINI15_5_GEO_COMPATIBILITY environment variable to 1 before saving the files in Houdini 16.0.


Unless you're able to update your 15.5 version you'll have to set the compatibility variable and rewrite your outputs from 16

It is backwards compatible, (i.e. Houdini 15.0/15.5 bgeo files can be opened in Houdini 16.0), but you need a more recent build of Houdini 15.0/15.5 for forwards compatibility, (i.e. so that Houdini 16.0 bgeo files can be opened in Houdini 15.0/15.5). Houdini 15.0.672+ and 15.5.669+ are able to load Houdini 16.0 bgeo files directly. (Also, I agree that the naming of those terms sounds reversed, but that's how they're defined.) The change drastically sped up saving of a large number of polygon or tetrahedron primitives, in some cases by 7x, but broke forwards compatibility.

If you need to go farther back than 15.0, or if you can't update Houdini 15.0/15.5 to a newer build, you can also set an environment variable HOUDINI15_5_GEO_COMPATIBILITY to the value 1 before starting Houdini 16.0, so that the files it saves will be forwards compatible.

I seem to recall there was also a bug with loading 2-float attributes (or maybe it was 4-float?) in earlier versions that were saved in Houdini 16.0, and I don't remember how many versions back the fix got backported. I know it got fixed in Houdini 15.5. If you run into that bug in something earlier than 15.5, I can backport the fix farther.

Edit: Changed text to “2-float” and “4-float”, to avoid confusing the forum post parser.

Thanks for the link, I couldn't get google or the forum search to turn up anything on the subject.

The thread seems to be hip file related though and 15 -> 16. I can understand there being minor changes to point order as nodes have to change or we'd never have any progress haha but to break the bgeo format seems unusual.

If this issue is related I would expect that the alembic file would fail to read as well but for it actually works so I wonder what it is about the new 16 bgeo that breaks the 15.5 read.

edit - Didnt see that post till after posting -brbreadingawesome


okay cool! bummer that it can't be read in 15.5.480 though.. I don't think I can convince IT to update the farm haha.
We'll see I guess.

Thanks so much for the help guys.

FXCore
bummer that it can't be read in 15.5.480 though.. I don't think I can convince IT to update the farm haha.

Setting HOUDINI15_5_GEO_COMPATIBILITY to 1 in Houdini 16.0 should help, then. If you've already saved out the bgeo files, you should be able to load them in Houdini 16.0 and save them back out with the environment variable set, and they should be fine to load in 15.5.480… unless you hit the 2-float (4-float?) bug. Best of luck!