[osg-users] Calculating Up Vector

[Cysneros, Nelson SPAWAR]

I got it working!!!

In case anyone is interested, this is what I did.

I took a local point on the -Z axis of the entity.  

localX = 0, localY=0, localZ=-1;

Converted it to World Coordinates (wX, wY, wZ), subtracted the center of
the entity in world coordinates.

Wx -= entityXWorld;
Wy -= entityYWorld;
Wz -= entityZWorld;

And used that for my UP vector 

osg::Vec3 up(Wx,Wy,Wz); 

What I think is happening is that my UP vector is attached to the top of
my entity now.  When the entity rolls, my UP vector rolls with it.


Works good  :)


-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of
Cysneros, Nelson SPAWAR
Sent: Thursday, February 28, 2008 10:35 AM
To: OpenSceneGraph Users
Subject: [osg-users] Calculating Up Vector


I'm having a problem trying to calculate the UP vector of a node as it
makes a 360 roll. 


I'm setting the camera viewpoint like this:

//Update View
osg::Vec3 eye( cameraX, cameraY, cameraZ);
osg::Vec3 center(nodeX,nodeY,nodeZ);
osg::Vec3 up(nodeX,nodeY,nodeZ); 
viewer->getCamera()->setViewMatrixAsLookAt(eye,center,up);

Which works great in a geoCentric system. I can place a node anywhere on
the earth and it will be right side up.

Now the node wants to make a 360 roll and we want the camera to roll
with it.  Not sure how to calculate the UP vector in this case.

I tried something like this:

osg::Matrix rotX, rotY, rotZ, transXYZ;
rotX.makeRotate(myNode->getXRotation(), osg::Vec3(1,0,0));
rotY.makeRotate(myNode->getYRotation(), osg::Vec3(0,1,0));
rotZ.makeRotate(myNode->getZRotation(), osg::Vec3(0,0,1)); up = eye ^
center;//cross product osg::Vec3 up2; 
up2   = up * rotZ * rotY * rotX;
viewer->getCamera()->setViewMatrixAsLookAt(eye,center,up2);


Does not work...  Any suggestions?

Thanks

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