Just rotation by btTransform

[frca]

Hello.
Is there a simpler way of doing this?

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btTransform transf;
btVector3 vect;
...
btVector3 rotatedVect = transf*vect-transf.getOrigin();

(I don't like that there is transf twice.)
Thanks.

[robagar]

How about this?

Code: Select all

transf.getRotation() * vect

[Flix]

btVector3 rotatedVect = transf*vect-transf.getOrigin();
(I don't like that there is transf twice.)

I would write:

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btVector3 rotatedVect = transf.getBasis() * vect;

so that I can just use the btMatrix3x3 reference that's already embedded inside the btTransform (without using its "origin" component).
I must check, but I think that "transf.getRotation()" converts the btMatrix3x3 to a btQuaternion (which is not needed); but I'm sure
robagar's intention was to point out the right approach (i.e. if you need to rotate a vector around a transform, you can just use its rotation).

[robagar]

yup you're right - using getBasis() is more efficient since it returns a reference & avoids the btQuaternion construction. Personally I'd use the quat anyway 'cos the intention is more clear (it's got the word "rotation" in there), unless I really needed it to be quick