[osg-users] About Changing Parental Nodes?

Ümit Uzun umituzun84 at gmail.com
Thu Jul 24 02:33:13 PDT 2008

Hi there,

Firstly thanks for useful replies. I know, this programmatic operation is
clumsy but I don't know any way to reorganize my 3d model structure. So I am
trying to handle my model's components and then I will write the created
scene in osg format. Then I can traverse the scene easily.

I succeed placing the components on the right place by using InverseMatrix
like below,


   osg::Matrixd mm1=planetaryTransformNode1->getInverseMatrix();
   osg::Matrixd mm2=planetaryTransformNode2->getInverseMatrix();

    osg::ref_ptr<osg::MatrixTransform> additionalMT = new
osg::MatrixTransform(mm1 * mm2);



When I perform this way to the additive node's Matrix Trasform, it can place
right position on the screen.

In right there, I have some question about defining center to the newly
created MatrixTrasform node. Because when I try to rotate the yawnode around
the Zup axes, it is rotating around the vec3(0.0,0.0;0.0) pivot point. If I
use a PositionAttitudeTrasform, I can define new pivot point easly but what
about MatrixTransform pivot point definitoin? And how can I get the GEODE
nodes world coordinate matrix to defining pivot point for the
MatrixTransform node?

Another question is, As you see from the structure of models, There is a 2
Matrix Transform ("3DSPIVOTPOINT: Rotate" and "3DSPIVOTPOINT: Translate
pivotpoint to (world) origin"). My planned structure, I will add one
MatrixTrasform for every node. Is it comes with unexpected error or
defectiveness in the future?

Thanks to everyone :)

Best Regards.


2008/7/24 David Spilling <david.spilling at gmail.com>:

> If I understand your problem correctly, the general approach would be to
> compute the coordinate system matrix local to a group prior to a move (with
> computeWorldToLocal) - call it A - then to move the node, recompute the
> coordinate system in the new location - call this B - and apply the correct
> matrix - i.e. inverse(B) * A -  to the immediate parent transform to get the
> correct positioning. In this way, when moving the object around in the
> scenegraph, it won't move in the world frame.
> In this case, the yaw group doesn't have a parent transform, so the initial
> matrix is the identity. The destination matrix will be the transform of
> planetary's MatrixTransform node, so you will need to apply the inverse of
> this matrix to your yaw specific MatrixTransform.
> I can't help but think that you must be able to persuade your 3DS model to
> be in a much more useful structure - all this programmatic model hacking
> (although useful for understanding OSG) seems quite clumsy...
> Regards,
> David
> _______________________________________________
> osg-users mailing list
> osg-users at lists.openscenegraph.org
> http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
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