PhysicsCharacter.onGround() is unreliable about libbulletjme HOT 7 CLOSED

Interesting that the issue doesn't appear in HelloCharacter.

from libbulletjme.

It appears in HelloGhost, but not if I configure the character's gravity to 59.9 psu/sec2 instead of 60.
And note that HelloCharacter uses the default gravity, which is 29.4 psu/sec2.

from libbulletjme.

Sure enough:

bool btKinematicCharacterController::onGround() const
{
	return (fabs(m_verticalVelocity) < SIMD_EPSILON) && (fabs(m_verticalOffset) < SIMD_EPSILON);
}

from libbulletjme.

btKinematicCharacterController is chock full of thoughtless hacks and copypasta. It could benefit greatly from a complete rewrite. But not today! The less I modify it, the happier I'll be. Ideally, I'd simply add an isOnGround() method to the jmeKcc subclass and invoke that in place of btKinematicCharacterController::onGround().

btKinematicCharacterController contains a few protected fields that seem relevant:

• m_wasOnGround is unfortunately set using the existing onGround() method, so no help there.
• full_drop has the opposite sense of onGround(). Unfortunately it is updated only if m_verticalVelocity <= 0.0, so it's not useful during the rising half of a jump.
• m_wasJumping has the opposite sense of onGround().

Of those 3 fields, m_wasJumping seems closest to providing the desired functionality. I've run a few tests, and it looks good.

from libbulletjme.

Okay, the fix is in Libbulletjme v14.5.0. In hindsight, I wish I'd made it return onGround() && !m_wasJumping;---less risk of a false positive that way.

from libbulletjme.

As written, TestPhysicsCharacter, TestQ3, and TestWalkingChar do not invoke onGround()---they permit jumping even when the character is airborne. In order to test this fix, those apps need minor modifications

from libbulletjme.

There's an issue with the current solution because it returns true after the character steps off the supporting surface. See the Forum discussion: https://hub.jmonkeyengine.org/t/linear-velocity-inconsistency-on-collisionlistener/47446/4

from libbulletjme.