OBJLoader enhancement: named groups support

[kkolyan]

What've done

OBJ model format has markup element to organize objects in groups (without nesting). Currently, this markup is ignored by jME's OBJLoader - only shape and material is loaded. This PR implements loading of groups as dedicated children of resulting Spatial.

Justification

In current verison there is no legitimate way of transfering any "tags" from model editor to game code with OBJ format models. This feature is vital for loading interactive models from OBJ format. Though OBJ format may be too primitive for serious modern character models, it's easy to support, it's tools-friendly, it's human-friendly, it's still supported by many editors and its capabilities are enough for static geometry modeling such as game areas for non-high-end games.

Forum discussion

https://hub.jmonkeyengine.org/t/objloader-enhancement-named-groups-support/43243

[8Keep]

Can you write a test for this? Or a sample for usage.

[kkolyan]

Can you write a test for this?

Sure:) Test added

Or a sample for usage.

where to place it? Or test is enough?

[stephengold]

Thanks for the testcase. Please move it from jme3-core to to jme3-examples/src/main/java/jme3test/model

[kkolyan]

what if I leave it here and create more demonstrative example in jme3test?

[stephengold]

OK.

[kkolyan]

Is it ok to move test model and material to jme3-testdata and add it as test dependency to jme3-core?
I mean to add

dependencies {
    testCompile project(':jme3-testdata')
}

to jm3-core/build.gradle.

Looks doubtfull, because as I see, you keep jme3-core build.gradle almost empty.

[stephengold]

I think it would be OK as a test dependency.

[kkolyan]

looks like checks failed due to some infrastructural problems

[stephengold]

I'll re-run those jobs.

[kkolyan]

It stills breaks. Looks like I handle text in non-portable way. Will fix later.

[kkolyan]

Is there some quota for check runs? This issue is Mac specific and I do not have Mac, so it may be necessary to run checks here many times. Is it ok?

[stephengold]

GitHub Actions is free for public repositories. As long as you're not intentionally abusing the servers, there shouldn't be any issues. https://help.github.com/en/github/setting-up-and-managing-billing-and-payments-on-github/about-billing-for-github-actions

[kkolyan]

comment in example updated

[stephengold]

I'll take a closer look today and hopefully integrate this PR.

[stephengold]

I looked, and I mostly liked what I saw. Apologies for the slowness of our PR process.

I like the new warnings for OBJ assets that contain merge groups or smoothing groups!

TestObjGroupsLoading is a clever test app ... though I wish it had an indicator in the center of the display to help the user aim the camera. A BitmapText containing "+" (as seen in TestBrickTower and many other examples) would be perfect. But that's a mere quibble that shouldn't prevent integration.

The main issue with this PR is simply that the 2 new source files ("ObjLoaderTest.java" and "TestObjGroupsLoading.java") lack licenses. Given the nuisance that issue #1001 has caused, I won't integrate those files without compatible licenses.

Please license these files, using similar source files are models.

[kkolyan]

crosshair and licences added.

[kkolyan]

sorry for non-convenient manner of ammend-force-push every commit. At work we never do so (we are ok with inflated history). But for jME I thought it's better to apply such little change as single squashed commit. Now I think it would be better to squash it only right before integration.

[stephengold]

I, too, would prefer to squash during integration, rather than having forced pushes. I'll take another look.

[stephengold]

Looks good. Thanks for your contribution to JMonkeyEngine!

[kkolyan]

Looks good. Thanks for your contribution to JMonkeyEngine!

I was glad to participate!