btTypedConstraintType and getWorldTransform() incorrect ?

[IresomPCH]

Hello,

I'm current testing the 2.83.5 version, and some minor issues shows up.

The btTypedConstraintType of btFixedConstraint returns D6_SPRING_2_CONSTRAINT_TYPE instead of FIXED_CONSTRAINT_TYPE.
It should be FIXED_CONSTRAINT_TYPE, right ?
(since the btFixedConstraint inherited from btGeneric6DofSpring2Constraint)
This issue exists since the 2.83.4 version.

Second, when calling btRigidBodyA->getWorldTransform() of btGeneric6DofSpring2Constraint, it always return an identity matrix.
However, the btRigidBodyB->getWorldTransform() works well.
On the other hand, btRigidBodyA->getWorldTransform() and btRigidBodyB->getWorldTransform() are both OK for btFixedConstraint...
This issue exists since the 2.83.5 version, not in 2.83.4.

Any ideas? Thanks~

[Erwin Coumans]

Hello,
The btTypedConstraintType of btFixedConstraint returns D6_SPRING_2_CONSTRAINT_TYPE instead of FIXED_CONSTRAINT_TYPE.
It should be FIXED_CONSTRAINT_TYPE, right ?

No, the btFixedConstraint is now derived from btGeneric6DofSpring2Constraint and doesn't override the serialization. When importing the data, is should return as a regular btGeneric6DofSpring2Constraint, but behave as a fixed constraint, all 6 DOFs are locked between the 2 bodies.

Second, when calling btRigidBodyA->getWorldTransform() of btGeneric6DofSpring2Constraint, it always return an identity matrix.

rigidBodyA and rigidBodyB of a btGeneric6DofSpring2Constraint returns the proper getWorldTransform here, without problem. Try attached is a modified file that shows correct behaviour, just run the example browser.

If you can reproduce it, please file an issue by modifying the examples/Constraints/Dof6Spring2Setup.cpp, you might have hit some special case.
Thanks,
Erwin

[anthrax11]

I think the confusion comes from the fact that FIXED_CONSTRAINT_TYPE is still defined in btTypedConstraintType. I've received this same question from a BulletSharp user.