[osg-users] Edit 3D (osgt) model to add DOFTransform and perform "node" rotation

Sun Apr 19 08:40:23 PDT 2020

Hi Jeremy, 

Step back for a second and think about what you are expecting. 

If your geometry is where it was before, after replacing the group with a PAT you’re totally fine. If the pivot point for your rotation is not what you’re expecting, then the geometry itself (vertices) might be translated.

That is why you need to figure out this point on your own. There is no magical way to deduce the point you want to rotate a geometry around, at least none that is not driven by some sort of heuristic.

If I find some time later, I’ll check the geometry you supplied and see if I spot something. In the meantime: Can you provide some info on the above? Does the resulting (untransformed) PAT-replaced hierarchy look the same as the original? And could you maybe supply the resulting file?

Cheers 

Sebastian 

From: osg-users <osg-users-bounces at lists.openscenegraph.org> On Behalf Of OpenSceneGraph Users
Sent: Sonntag, 19. April 2020 16:36
To: OpenSceneGraph Users <osg-users at googlegroups.com>
Subject: Re: [osg-users] Edit 3D (osgt) model to add DOFTransform and perform "node" rotation

Almost everything is under control at this point, except one piece of black magic. Successfully 1) finding node of interest (via NodeVisitor) and add to transform, 2) get parent and child information, 3) remove old child 4) add new transform to appropriate parent

The model structure doesn't include any useful transforms. At the point of interest the model components are being geode, group or geometry. None of these structure have the appropriate information ( important one being pivot point ) that can be extracted to applied to the new transform.

On Saturday, April 18, 2020 at 11:06:08 AM UTC-4, Jeremy W wrote:

Sebastian

I'll experiment with removing the original group.

The original model structure doesn't include any transforms. So the structure I am looking at right now is:

Group "Heli" -> MyNewPAT -> Group "Main_Hub" -> Geometry1 ... GeometryN

If the MyNewPAT either child or parent was an object that contain the appropriate information such as pivot I could definitely extract that info and apply it to the PAT, but unfortunately it's surrounded by Groups.

Maybe I could create both a transform and a PAT, but I would still need some of that basic information to set its reference points.

I've attached an osgt example.

Thanks

Jeremy

On Saturday, April 18, 2020 at 6:53:10 AM UTC-4, OpenSceneGraph Users wrote:

Hi, 

you’re on the right track. Issue 1 stems from the fact, that you are not removing the original group or at least the childs you’re re-parenting (which still has references to your nodes).

Concerning issue 2. If the parent is a transform, you obviously need to take this into account. PAT has a setPivotPoint IIRC, but another option is to structure your scenegraph as follows:

Group -> OrginalTransform/Parent -> YourNewPAT -> Geometry1 … GeometryN

So leave the transform an put your PAT inbetween. That should solve the offset. If you’re still struggling with this, maybe supply a minimal osgt.

Cheers 
Sebastian 

From: osg-users <osg-user... at lists.openscenegraph.org <mailto:osg-user... at lists.openscenegraph.org> > On Behalf Of OpenSceneGraph Users
Sent: Samstag, 18. April 2020 01:38
To: OpenSceneGraph Users <osg-... at googlegroups.com <mailto:osg-... at googlegroups.com> >
Subject: Re: [osg-users] Edit 3D (osgt) model to add DOFTransform and perform "node" rotation

Sebastian

Thank you for your patience and guidance. Programmatically definitely makes sense and I did look into that a short while back. I was initially looking at PositionAttitudeTransform. Now revisiting that approach, I understand why I started to look in another direction. Here is the dilemma I've come across. All is good until I try to assign a parent to the Transform 

hive::display::FindNamedNodeVisitor fnnv("Main_Hub");

scene->accept(fnnv);

osg::ref_ptr <osg::PositionAttitudeTransform> autoTrans = new osg:: PositionAttitudeTransform();

//puts node and all children under transform

autoTrans->addChild(fnnv.getFoundNode());

//set the parent (this doesn’t seem completely right to me, but may be)

fnnv.getFoundNode()->getParent(0)->addChild(autoTrans);

issue 1) at this point it appears to create a duplicate object (node and children) of the “Main_Hub” group; 

issue 2) when I attempt rotation of the object it seems to be around the origin of the model instead of the previous “pivot pilot”

I seem to be missing how to squeeze that transform between the parent and child appropriately.

Jeremy

On Thursday, April 16, 2020 at 9:41:55 AM UTC-4, OpenSceneGraph Users wrote:

Hi Jeremy, 

Yes programmatically. You simply create a  Transform, DOFTransform, whatever and set all the children of the original Group as childs of the new one (transforms, as you surely know are groups too).

Lastly you want to want to set the parent as well. I haven’t used OSG in a while, but this pattern for sure works. 

If you have more questions fell free to ask.

Cheers 

Sebastian 

From: osg-users <osg-user... at lists.openscenegraph.org <mailto:osg-user... at lists.openscenegraph.org> > On Behalf Of OpenSceneGraph Users
Sent: Donnerstag, 16. April 2020 14:36
To: OpenSceneGraph Users <osg-... at googlegroups.com <mailto:osg-... at googlegroups.com> >
Subject: Re: [osg-users] Edit 3D (osgt) model to add DOFTransform and perform "node" rotation

Sebastian, I've used the nodevisitor to find the node by name, the node just happens to be a osg::group. Could you explain what you mean by "replace them with a DOF-Transform"? I'm optimistic that you mean programmatically. My current approach is to replace it manually in the osgt file.

Thanks

Jeremy

On Thursday, April 16, 2020 at 7:14:18 AM UTC-4, OpenSceneGraph Users wrote:

Hi Jeremy, 

As your geometry-parts are usually under a transform /group you can use a NodeVisitor to collect those (Find the nodes by name) and replace them with a DOF-Transform. 

You could of course also mess with the osgt-files, but that would be a last resort. 

Cheers

Sebastian 

From: osg-users <osg-user... at lists.openscenegraph.org <mailto:osg-user... at lists.openscenegraph.org> > On Behalf Of OpenSceneGraph Users
Sent: Mittwoch, 15. April 2020 21:54
To: OpenSceneGraph Users <osg-... at googlegroups.com <mailto:osg-... at googlegroups.com> >
Subject: [osg-users] Edit 3D (osgt) model to add DOFTransform and perform "node" rotation

First off, I hope everyone is staying sane and healthy during this pandemic.

I’m working with a collection of 3D models that have come from a variety of different source but are now all in osgb format. For several of the models I’d like to grab a “node” and apply rotation.

As I’m working through my understanding of the approach, I’ve created a simple application that loads the model, traverses the scene, returns a pointer to the “node”, casts to a DOFTransform and manipulate the “node” (DOFTransform). Snippet:

FindNamedNodeVisitor fnnv("turret");

scene->accept(fnnv);

osg::ref_ptr<osgSim::DOFTransform> dofTrans = new osgSim::DOFTransform();

dofTrans = dynamic_cast<osgSim::DOFTransform*>(fnnv.getFoundNode()->asTransform());

if(dofTrans != NULL)

                                //manipulate (rotate)   

This approach works for the tank.osg model. Now I’m trying to apply this approach to a different model (helicopter for example). When I access the “node” of interest, “Main_Hub” which is an osg::Group I obviously can’t cast that to a osgSim::DOFTransform. I’m trying to get an understand of how I can change the model, now in osgt (readable) format, to a structure that can be used. I’ve been using the tank.osg as a guide and attempted to recreate a similar structure in the helicopter.osgt. I’m trying to take logical stabs in the dark, in the helicopter model I’ve attempted to simply renamed the “node” of interest from an osg::Group to osgSim::DOFTransform. The model still displays correctly, but the cast to osgSim::DOFTransform returns NULL. I thought there may be some required variables at are needed as part of the osgSim::DOFTransform structure, so I began adding currentHPR, currentTranslate, and currentScale and continued to add more bringing it in line with the tank.osg example. Through all the attempts I still getting NULL when casting.

I’m looking for any guidance/suggestions/lessons learned on how to properly do this.

Thanks in advance

Jeremy

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