Rotation around specified centre

[Abraxas]

Hello,

well, possibly for you easy to answer, in spite of me:

I want to let meshes rotate around a specified centre, which will be defined (another mesh, e.g.)and will have to change this centre point sometimes.
Also I should have to define the radius and the angle of the rotation.

Is there any pre-defined action in irrlicht to do that?

[bitplane]

thingpos = pivotpos + (thingPos - pivotPos).rotateXYBy(whatever)
or whatever

[krama757]

Not that I know of. I would just use some polar coords and some angle math.

I dont think its too complicated.

But that coming from a guy who loves math doesnt help ^_^

[Spintz]

The fastest way is to subtract the point that represents the center of rotation from the position of the node. Then, do normal rotation and then add back the position of the rotation point. For example :

Code: Select all

core::vector3df pivotPoint( 100, 100, 100 );
core::vector3df tempPos = node->getPosition();
tempPos -= pivotPoint;
core::matrix4 rotMat;
rotMat.setRotationDegrees( core::vector3df( 45, 45, 45 ) );
rotMat.rotateVect( tempPos );
node->setPosition( tempPos + pivotPoint );

Note: you may have to call setInverseRotationDegrees, instead of setRotationDegrees.

I don't know what you mean by radius. What does the radius have to do with rotation? I guess, the radius of the rotation is the distance from the pivotPoint to the position of the node. But it's not needed in this case.

[bearSoft]

the radius imply that Abraxas want an -orbit- around an instance (pivotpoint)
i know the formula -but there is also the rotationAnimator..
Wouldent it be the simplest way?
The gfx tut has an orbitting light source..
but change it in game loop..
hmm.. :shock:

[genesisrage]

i havent tried this with irrlicht, but some other engines ive used will actually rotate an object around the stored pivot point (that can be moved in max). does irrlicht use that info, or does it just set the pivot point at the center of the model?