Real-Time Physics Simulation Forum

@StabInTheDark, oh right I forgot that I had to hack the Bullet source code for NULL_CONSTRAINT_TYPE. I just added it near the end of the enumerated types in .../src/BulletDynamics/ConstraintSolver/btTypedConstraint.h, right above MAX_CONSTRAINT_TYPE. The reason I added that custom constraint was be...

Looking at the code it appears that the "data" argument of btDbvt::insert() is a just void* to whatever object is contained within the corresponding volume. That is, the btDbvt class is agnostic about "what" is actually contained in its nodes. The btDbvtNode struct keeps track of...

I would guess that a ray test might actually rely on the broadphase data structure to make the test fast. If so then it would require that the AABB's are updated for correct results.

I think maybe why your two objects are not colliding is because of the collision group/mask settings in addCollisionObject(). It appears that you're setting the group of the two objects to be group = btCollisionObject::CF_CHARACTER_OBJECT (16), but they only collide with mask = btBroadphaseProxy::St...

When it comes to peforming the collision test: you need to carefully read the wiki page about "Collision Callbacks and Triggers", in particular the section called "contactTest". There is example code there that you should examine carefully so you know what it is doing, but you sh...

I've been evaluating the Bullet physics engine for use in a virtual world project (highfidelity.io). In particular I wanted to find out if Bullet could simulate an articulated character. To that end I started with the 2.82 Ragdoll demo and added a custom internalTickCallback() that pulls the collect...

That sounds correct. If you aren't "stepping" the world normally then there would be some methods that you would have to call manually. I usually find the that the Bullet documentation doesn't provide enough info for method calls, such as expected units or acceptable ranges. The good thing...

My suggestion would work for any shape. You could even use cylinders or spheres if they were a better approximation for your character's footprint along the path. A nice thing about using a SphereShape would be that the orientation of a claim object wouldn't matter at all. There is no AabbShape, ins...

Does your python implementation compute the theoretical curve or does it do a simulation with timesteps? If it computes the theoretical curve then one thing to try is to play with the timestep of the bullet simulation to see if it get better with smaller steps and worse with larger. If it performs a...

Another idea: I think there is some default damping in the Bullet physics engine but I'm not sure how to turn it off. You can work around the damping (e.g. make it negligible) by increasing the mass of your block. Since you're colliding a block with mass against a ramp with infinite mass there are n...

Perhaps I see what you mean. Let me repeat it back to see if it makes sense. A character plans on where it wants to go and "claims" its path by plopping down instances of its own shape along the path (after first checking to make sure none of those spots are in contention with claims by ot...

I take it back, there was no bug in btRigidBody::applyImpulse(). The logic makes sense in the special case where I "discovered" the bug, but not in general. I closed the pull request that I had created. However, it turns out that when applyImpulse() is used to apply a unit of impulse at an...

Yeah, I take it back. There is no bug in btRigidBody::applyImpulse(). My logic applies to the special case I was working on when I "discovered" the bug, but not in general. I closed that pull request. I guess the discrepancy of static friction in Bullet from the theoretical is just a quirk...

Do you just want to know how an OBB collides with the ground? Or is there something more detailed inside the OBB that you want to collide with the ground? If you just want to collide OBB's against the ground then you can just give your btCollisionObject a btBoxShape -- the BoxShape is its own OBB an...

Today I noticed a bug in btRigidBody::applyImpulse() where the linear component of impulse is not correctly computed when the impulse is applied at a non-zero offset from the RigidBody's center of mass. I've submitted a fix for the bug here: https://github.com/bulletphysics/bullet3/pull/272 It occur...