Search found 28 matches

by kingchurch
Mon Sep 07, 2015 9:04 am
Forum: General Bullet Physics Support and Feedback
Topic: Building articulated character with btMultiBody
Replies: 8
Views: 4218

Re: Building articulated character with btMultiBody

Motor/limit constraints are not currently supported for spherical links of btMultiBody. However nothing prevents you from implementing your own force motor by applying a force/torque to the spherical links directly. But pay attention that the joint positions returned for spherical links is Quaternio...
by kingchurch
Wed Jun 10, 2015 10:39 pm
Forum: General Bullet Physics Support and Feedback
Topic: BT_USE_DOUBLE_PRECISION performance on Neon/iOS
Replies: 1
Views: 1654

BT_USE_DOUBLE_PRECISION performance on Neon/iOS

Does the Neon/iOS vector math acceleration only support single precision float ? When BT_USE_DOUBLE_PRECISION is defined do we expect a slowdown in Neon's linear math (vector, matrix operations) performance ? Thanks!
by kingchurch
Wed Jun 10, 2015 10:34 pm
Forum: General Bullet Physics Support and Feedback
Topic: CPU multithreading is working!
Replies: 145
Views: 85746

Re: CPU multithreading is working!

Awesome work! Will the multi-threading optimization work on iOS/Neon processors ?
by kingchurch
Mon Jun 08, 2015 5:12 am
Forum: General Bullet Physics Support and Feedback
Topic: How to read joint reaction force from btMultiBody
Replies: 0
Views: 2269

How to read joint reaction force from btMultiBody

With btRigidBody and joints we can read the joint reaction force (for joint breaking feature and such) from the "appliedImpulse" in the joints/constraints. How do we read such joint reaction force from the joints built-in a btMultiBody model ? Do we have this feature calculated in the Featherstone s...
by kingchurch
Wed Jan 14, 2015 10:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rotation Parameterization for btMultiBodyJointMotor
Replies: 0
Views: 2204

Rotation Parameterization for btMultiBodyJointMotor

I have a question that how is the Featherstone ball socket joint's 3 DOF parameterized. More specifically when we setup a btMultiBodyJointMotor or btMultiBodyJointLimitConstraint to constrain the motion of the 3DOF of the Featherstone ball socket joint are the 3DOFs that are motorized or limited the...
by kingchurch
Tue Dec 16, 2014 10:25 pm
Forum: General Bullet Physics Support and Feedback
Topic: CPU multithreading is working!
Replies: 145
Views: 85746

Re: CPU multithreading is working!

Exciting! Will the MT version work on iOS devices ?
by kingchurch
Wed Dec 10, 2014 7:21 am
Forum: General Bullet Physics Support and Feedback
Topic: fuzzyZero assertion error
Replies: 6
Views: 5531

Re: fuzzyZero assertion error

I just changed it to return the vector itself if it's close to zero. Because most of time when you call Normalize() you expect it to do nothing if the vector is almost a 0 vector. Returning a infinitely large value is rarely a good idea. Everyone wants documentation but no one actually does any docu...
by kingchurch
Thu Nov 20, 2014 10:44 pm
Forum: General Bullet Physics Support and Feedback
Topic: btMultiBody instability (character shoots up into the air)
Replies: 5
Views: 4873

Re: btMultiBody instability (character shoots up into the ai

Update: I tested Simbody again using SimTK::Integrator::setFixedStepSize to fix the timestep. With the timestep fixed to 33 ms, the bodies hit the floor nicely. However in Simbody when the bodies are laying on the floor, they don't come to rest as easily as they do in Bullet. They wiggle and squirm...
by kingchurch
Thu Nov 20, 2014 10:28 pm
Forum: General Bullet Physics Support and Feedback
Topic: Is it safe to dispose of shapes/rigid bodies in a thread?
Replies: 10
Views: 6024

Re: Is it safe to dispose of shapes/rigid bodies in a thread

Some comments on the wrapper and duplicate object list: P-Invoke interface is notoriasly slow. Even though the C# code in the wrapper function only takes micro seconds and the C++ side Bullet code only takes microseconds, the P-Invoke API marshaling code that transforms managed call convention into ...
by kingchurch
Tue Nov 18, 2014 8:01 pm
Forum: General Bullet Physics Support and Feedback
Topic: btMultiBody instability (character shoots up into the air)
Replies: 5
Views: 4873

Re: btMultiBody instability (character shoots up into the ai

With 22 btMultiBody and a timestep of 700 microseconds, none of the btMultiBody instances shoot up into the air, which is good. I'm hoping that with some improvements to Bullet's Featherstone implementation, I won't need such a small timestep, but I'm also hoping that when Bullet 3.0 is released I'...
by kingchurch
Tue Nov 18, 2014 12:57 am
Forum: General Bullet Physics Support and Feedback
Topic: Problem with vibrating bodies (alt. Character riding a bike)
Replies: 4
Views: 4258

Re: Problem with vibrating bodies (alt. Character riding a b

Anyone got some clues to what might cause these vibrations? Is it expected that multiple bodies connected to each other in this chain/circle-like manner will behave like this? https://s3-eu-west-1.amazonaws.com/j0nas.se/bmx/vibrations.gif One possible reason of the instability is the close loop top...
by kingchurch
Tue Sep 16, 2014 8:52 pm
Forum: General Bullet Physics Support and Feedback
Topic: Correct way to implement a gripper
Replies: 6
Views: 5466

Re: Correct way to implement a gripper

What did you mean by "they repel each other" ? Do you mean the finger bounced off the block ? If that's the case try assign a physics material with 0 restitution (bounciness) and 1.0 friction coefficient. Also make your motor/finger torques stronger. And increase the #of iterations of the solver. Re...
by kingchurch
Thu Sep 04, 2014 8:57 pm
Forum: General Bullet Physics Support and Feedback
Topic: Can we create a RigidBody without a CollisionObject ?
Replies: 1
Views: 2196

Can we create a RigidBody without a CollisionObject ?

Is that possible to create a RigidBody with a mass and inertia but without a collision object attached to it ? This is so we can disable collision on selected rigid bodies without the overhead of conducting broad/narrow phase of collision objects ? I know that we can achieve this effect with collisi...
by kingchurch
Mon Jul 21, 2014 5:29 pm
Forum: General Bullet Physics Support and Feedback
Topic: Rubber band constraints
Replies: 3
Views: 3666

Re: Rubber band constraints

The 6DOF spring joint is a soft-constraint based 6DOF constraint to my understanding (see other thread in the forum on the joint limits of this joint). What you need is a point-to-point spring between the cursor and the body under manipulation. You can implement a p2p spring in different ways. For e...