Search found 698 matches

by drleviathan
Wed Nov 04, 2020 8:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rotating one object at the expense of the second
Replies: 7
Views: 1935

Re: Rotating one object at the expense of the second

Dunno what is causing your "bounce". Does the dynamic object fall onto the kinematic floor and bounce only when it first touches? Or does it bounce constantly as the simulation continues? Perhaps it is a tunneling penetration resolution glitch: what are your steps, substeps, and min_num_su...
by drleviathan
Tue Nov 03, 2020 10:29 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rotating one object at the expense of the second
Replies: 7
Views: 1935

Re: Rotating one object at the expense of the second

If I understand what you're asking (correct me if I'm wrong): you want to have a dynamic object dragged around when it sits on a rotating kinematic "floor". The trick is: not only do you have to rotate the kinematic floor but you must also set its velocities to agree with its movement. The...
by drleviathan
Mon Oct 26, 2020 5:47 pm
Forum: General Bullet Physics Support and Feedback
Topic: Applying a torque to a sphere around a given axis
Replies: 2
Views: 1004

Re: Applying a torque to a sphere around a given axis

As per the documentation these methods are available for btRigidBody and can apply torque directly: void applyTorque (const btVector3 &torque) void applyTorqueImpulse (const btVector3 &torque) void applyImpulse (const btVector3 &impulse, const btVector3 &rel_pos) However, those only ...
by drleviathan
Thu Oct 22, 2020 3:01 pm
Forum: General Bullet Physics Support and Feedback
Topic: Screw Fastening Simulation
Replies: 1
Views: 781

Re: Screw Fastening Simulation

Do you want to simulate accurate or semi-accurate physics of threaded nut on bolt? Or do you just want an interactive threaded nut on bolt behavior (e.g. as a game mechanic)? If the former then Bullet might not be accurate enough, since it is a rigid body simulation and accurate nut on bolt physics,...
by drleviathan
Mon Oct 19, 2020 4:56 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to rotate rigid body around Y and Z axis independently and simultaneously?
Replies: 12
Views: 2727

Re: How to rotate rigid body around Y and Z axis independently and simultaneously?

Ah I see the controls now. Yeah, I tried lots of values and could not get anything that looks like a varial. In fact, I was having trouble getting the skateboard tips to flip front to back on landing for anything. I could contrive to land some fancy flips but the front would return to facing forward...
by drleviathan
Mon Oct 19, 2020 4:28 pm
Forum: General Bullet Physics Support and Feedback
Topic: Advice needed on implementation of a physical VR character controller
Replies: 1
Views: 753

Re: Advice needed on implementation of a physical VR character controller

I bet there is a way to solve your snap-turn and smooth-turn problems when using a dynamic character but I don't know enough of your setup to be sure. Nevertheless I will offer advice for things to try: (1) Instead of imparting forces/torques to move/orient your character try slamming its velocities...
by drleviathan
Sat Oct 17, 2020 4:44 pm
Forum: General Bullet Physics Support and Feedback
Topic: Problem with character controller and btHeightfieldTerrainShape
Replies: 2
Views: 920

Re: Problem with character controller and btHeightfieldTerrainShape

Mmmmaybe... but it is not clear. I have experienced the case where hidden normals introduce odd collision directions on a flat btBvhTriangleMeshShape surface. My understanding is: btHeightfieldTerrainShape builds temporary btTriangleShapes instances as necessary whereas btBvhTriangleMeshShape caches...
by drleviathan
Fri Oct 16, 2020 11:09 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to rotate rigid body around Y and Z axis independently and simultaneously?
Replies: 12
Views: 2727

Re: How to rotate rigid body around Y and Z axis independently and simultaneously?

Hrm... the V button wasn't doing anything for me, but I did manage to land a kick-flip. Looking back at what I said... I would add: (a) The numbers I was using were for a board that was starting its varial part while already kicked nose-up about 45 degrees. If your simple varial is starting with the...
by drleviathan
Wed Oct 14, 2020 8:35 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to rotate rigid body around Y and Z axis independently and simultaneously?
Replies: 12
Views: 2727

Re: How to rotate rigid body around Y and Z axis independently and simultaneously?

How do I calculate the angular velocity of the desired varial (tumble phase)? That is the question. I don't know, but I've been thinking about it: (1) I wonder if my assumption that the angular velocity remains constant for the duration of the tumble is valid. The board needs to perform a full twis...
by drleviathan
Wed Oct 14, 2020 4:24 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to rotate rigid body around Y and Z axis independently and simultaneously?
Replies: 12
Views: 2727

Re: How to rotate rigid body around Y and Z axis independently and simultaneously?

Yes, you could apply impulses (or better yet: just slam the angular velocity) to follow a "keyframe" of rotations. That is pretty much what I'm suggesting except I claim there are only (as I count them)... one, two, three... inflection points in minimal keyframe path. Or to put it another ...
by drleviathan
Wed Oct 14, 2020 2:34 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to rotate rigid body around Y and Z axis independently and simultaneously?
Replies: 12
Views: 2727

Re: How to rotate rigid body around Y and Z axis independently and simultaneously?

First of all I should mention: I now realize my recipe for making a varial is incorrect. The step where the delta rotation Q01 is computed is wrong because I was assuming the skateboard would take the shortest possible rotation from Q0 to Q1 and that is not what happens. It actually takes a more cir...
by drleviathan
Wed Oct 14, 2020 1:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: collision problem - broadphase pair
Replies: 3
Views: 1089

Re: collision problem - broadphase pair

So if at at instant Y, after i moved the object and called the PerformDiscreteCollisionDetection , I don't receive the expected pair in the needBroadphaseCollision it can only means that the bound proxies don't overlap. Is it right? I believe that is correct. The needBroadphaseCollision would be ca...
by drleviathan
Tue Oct 13, 2020 3:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: collision problem - broadphase pair
Replies: 3
Views: 1089

Re: collision problem - broadphase pair

The btOverlappingPairCache::needsBroadphaseCollision() implementation looks like this: SIMD_FORCE_INLINE bool needsBroadphaseCollision(btBroadphaseProxy * proxy0, btBroadphaseProxy * proxy1) const { if (m_overlapFilterCallback) return m_overlapFilterCallback->needBroadphaseCollision(proxy0, proxy1);...
by drleviathan
Fri Oct 09, 2020 4:17 pm
Forum: General Bullet Physics Support and Feedback
Topic: How to rotate rigid body around Y and Z axis independently and simultaneously?
Replies: 12
Views: 2727

Re: How to rotate rigid body around Y and Z axis independently and simultaneously?

Your skate simulation looks nice. It is off to a good start. I watched the varial video carefully and played around with your sim. I have some ideas about things you could try, but first some feedback/perspective: In physical games there are often trade offs between realistic physics and fun/playabi...
by drleviathan
Mon Aug 31, 2020 2:32 am
Forum: General Bullet Physics Support and Feedback
Topic: btDbvt broadphase stages and tree
Replies: 1
Views: 1156

Re: btDbvt broadphase stages and tree

I don't have any good ideas about how one might dig into the internals of the btDbvt broadphase to feed your AI, however it is possible to use a btPairCachingGhostObject to help optimize tracking of nearby objects. The normal scenario goes something like this: You have a Character who needs to know ...