What is Point Groups in OBJ export settings ?

PetSto

Hi,

I tryed google whole day, but I can't find, what is meant under this settings, what exactly doing this option ?

Thanks.

monster

What software are you using?

Jeff

It's a wavefront OBJ format specification.
It defines the "separate objects" merged into a "single obj" export.
A bit like a selection set, but in such a way it can be passed to another application, as it's embedded in the OBJ.

- Mari uses them in order to setup face groups when loading OBJ
- 3DCoat uses the info to split OBJ into sub objects
- Mudbox automatically splits the merged OBJ into separate objects, even keeping the original names !
- etc ...

Not to say that not many applications use them thoroughly, but more often making the split through initialy assigned materials ID.

Hope that helps

PetSto

monster wrote: »

What software are you using?

I'am using Maya.

Jeff wrote: »

It's a wavefront OBJ format specification.
It defines the "separate objects" merged into a "single obj" export.
A bit like a selection set, but in such a way it can be passed to another application, as it's embedded in the OBJ.

- Mari uses them in order to setup face groups when loading OBJ
- 3DCoat uses the info to split OBJ into sub objects
- Mudbox automatically splits the merged OBJ into separate objects, even keeping the original names !
- etc ...

Not to say that not many applications use them thoroughly, but more often making the split through initialy assigned materials ID.

Hope that helps

Sry, I still don't understand that I have read specification http://www.martinreddy.net/gfx/3d/OBJ.spec and I can't find mention of point groups, how look's in code and how can I reproduce this in Maya.

Only what is mentioned in specification was classic groups, but there are strange too. When I have 2 objects and then I export and reimport back with groups off to Maya, then objects are combined. When has groups on, then objects are as separated pieces with correct names. Everything is as I expected.

But when put these 2 objects in to some group and in export have groups on and reimport it back, then Maya don't know how right import this group wth 2 separated objects, don't remember names and crated some parts separated from object with vertices, faces inside some groups. And of course when importing then Maya told me:
"Your OBJ file contains faces shared by multiple groups. Maya cannot create multiple objects for this file. A single mesh object will be created instead. The OBJ group information will be captured in Maya sets."

Jeff

Hello there,

Sorry, I understood your question was about the "points group" option.
I don't know about the "group" option.
But yes, true it only works as expected when selected meshes are contained in the root of the outliner. If these meshes are contained in a outliner's group, Maya converts the separate obj into selection groups on a merged object, which is what bothers you, and I agree it's totally weird, not to say nonsense.
>> for such interops between 2 Mayas, I never use obj, but rather fbx.

A trick for Maya's interop, through MEL script, might be to export these meshes (from the root outliner), with an obj's name representing the group-name you want these meshes in. And when importing this obj file, recreate the group and put the contained obj meshes into the newly created group (named as the obj file) ?

Also, not to say rubbish about specs, subject to various interpretations & cases, I would advise you to wait for someone diving deep into these kinda bits.

I know only one guy probably able to provide the full detailed answer, so I'll try this way. Coming back to you if I got some convincing answer