[Feature request] Implement gravity override for all bodies and not just vehicle constraints

[PiMoNFeeD]

In my project, I want to be able to override gravity on per-object basis, and while I could mess with gravity factor, that won't help when my global gravity shifts if I want my overridden gravity to stay the same. That would also help make vehicle constraint implementation cleaner, as that won't need to do the hack of setting vehicle gravity factor to 0 and instead applying it manually.

[jrouwe]

Hello,

I'm currently not planning to create a property to do this since it is really easy to implement per object custom gravity yourself, see:

JoltPhysics/Samples/Tests/Character/CharacterPlanetTest.cpp

Lines 173 to 198 in 1bc02f6

	void CharacterPlanetTest::OnStep(float inDeltaTime, PhysicsSystem &inPhysicsSystem)
	{
	// Use the length of the global gravity vector
	float gravity = inPhysicsSystem.GetGravity().Length();
	// We don't need to lock the bodies since they're already locked in the OnStep callback.
	// Note that this means we're responsible for avoiding race conditions with other step listeners while accessing bodies.
	// We know that this is safe because in this demo there's only one step listener.
	const BodyLockInterface &body_interface = inPhysicsSystem.GetBodyLockInterfaceNoLock();
	// Loop over all active bodies
	BodyIDVector body_ids;
	inPhysicsSystem.GetActiveBodies(EBodyType::RigidBody, body_ids);
	for (const BodyID &id : body_ids)
	{
	BodyLockWrite lock(body_interface, id);
	if (lock.Succeeded())
	{
	// Apply gravity towards the center of the planet
	Body &body = lock.GetBody();
	RVec3 position = body.GetPosition();
	float mass = 1.0f / body.GetMotionProperties()->GetInverseMass();
	body.AddForce(-gravity * mass * Vec3(position).Normalized());
	}
	}
	}

[PiMoNFeeD]

That would require me to set gravity factor to 0 so it doesn't apply it on it's own, right?

[jrouwe]

Correct