Search found 50 matches

by bram
Fri Dec 21, 2018 7:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: m_linearFactor
Replies: 1
Views: 208

m_linearFactor

What is the function of btRigidBody's m_linearFactor member variable?

It is set by ::setLinearFactor() function.

But a grep on the source code doesn't show a single use of this function?
by bram
Fri Dec 21, 2018 1:56 am
Forum: General Bullet Physics Support and Feedback
Topic: Mass values.
Replies: 3
Views: 354

Re: Mass values.

It turns out that it's super easy to reproduce in BenchmarkDemo.cpp with a single line change.

Details here:

https://github.com/bulletphysics/bullet3/issues/2033
by bram
Fri Dec 21, 2018 1:40 am
Forum: General Bullet Physics Support and Feedback
Topic: Mass values.
Replies: 3
Views: 354

Re: Mass values.

Yes, I'll try to repro it in the Benchmark Convex Demo.
by bram
Thu Dec 20, 2018 6:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Mass values.
Replies: 3
Views: 354

Mass values.

So, I have a ground plane that is colliding with convex hull shapes. This works well, at low mass values. But if I create a larger shape, with a larger mass, let's say above the 20.0 value, then the fragments sink through the ground plane. I understand that large mass ratios for joints are not stabl...
by bram
Thu Dec 20, 2018 6:08 pm
Forum: General Bullet Physics Support and Feedback
Topic: ghost object is sticky, holds onto objects too long [with video]
Replies: 2
Views: 375

Re: ghost object is sticky, holds onto objects too long [with video]

Maybe it is the default 0.02 margin?

Code: Select all

virtual void btCollisionShape::setMargin 	( 	btScalar  	margin	) 	
What's the scale of those spheres? Try setting the margin to 0.001 and see if it changes.
by bram
Tue Dec 11, 2018 8:35 pm
Forum: General Bullet Physics Support and Feedback
Topic: Equivalent of OpenDE's space?
Replies: 3
Views: 1557

Re: Equivalent of OpenDE's space?

Thx, For people trying to replicate this: you have to go through the cache, like so: broadphase->getOverlappingPairCache()->setOverlapFilterCallback(...) I decided to use btCollisionObject's userIndex for the grouping per vehicle. But note: because the information is cached, you need to set the user...
by bram
Fri Dec 07, 2018 2:57 am
Forum: General Bullet Physics Support and Feedback
Topic: Trouble with ray testing
Replies: 2
Views: 314

Re: Trouble with ray testing

Yeah, that sounds plausible, indeed.

If it's a NaN, you can catch them, right at the moment that they are generated, with:

Code: Select all

#include <fenv.h>
feenableexcept( FE_DIVBYZERO | FE_INVALID | FE_OVERFLOW );
or on windows:

Code: Select all

#pragma float_control( except, on )
...or use /fp:except compiler option.
by bram
Mon Nov 26, 2018 5:17 am
Forum: General Bullet Physics Support and Feedback
Topic: Dynamically skipping collision response.
Replies: 2
Views: 294

Re: Dynamically skipping collision response.

Excellent, this works just fine. Thanks for the suggestion.
by bram
Mon Nov 26, 2018 4:11 am
Forum: General Bullet Physics Support and Feedback
Topic: Dynamically skipping collision response.
Replies: 2
Views: 294

Dynamically skipping collision response.

I am using gContactProcessedCallback so that I can control the collision response, on the fly. This works well so far (I use it to implement a more complex friction behaviour.) However, in some cases, I want dynamically have the option to decide to have no contact response. What I tried was have my ...
by bram
Sat Nov 24, 2018 3:25 am
Forum: General Bullet Physics Support and Feedback
Topic: Generating Contact Constraints.
Replies: 6
Views: 665

Re: Generating Contact Constraints.

Excellent!

BT_CONTACT_FLAG_LATERAL_FRICTION_INITIALIZED was indeed the missing ingredient.

I can now control tyre/road friction the way I need it.
I'm confident I can now get a nice handling vehicle without having to resort to ray tests as wheels.

Thanks again!
by bram
Sat Nov 24, 2018 12:50 am
Forum: General Bullet Physics Support and Feedback
Topic: Generating Contact Constraints.
Replies: 6
Views: 665

Re: Generating Contact Constraints.

Thanks Erwin, I appreciate it. Although I understand it a little better now, it is still not working. I now get 'Added' callbacks, with the CUSTOM MATERIAL flag set. CHECK . If I set m_combinedFriction to 0 in that callback, the tyres slide as expected. CHECK . So lateralFrictionDir1/2 are scaled di...
by bram
Fri Nov 23, 2018 10:24 pm
Forum: General Bullet Physics Support and Feedback
Topic: Different types of friction.
Replies: 7
Views: 706

Re: Different types of friction.

Thx, I can't get the 'Added' callback be actually called. The 'Processed' callback is though. si.m_solverMode = SOLVER_USE_WARMSTARTING | SOLVER_SIMD | SOLVER_RANDMIZE_ORDER | SOLVER_DISABLE_IMPLICIT_CONE_FRICTION | SOLVER_ENABLE_FRICTION_DIRECTION_CACHING | SOLVER_USE_2_FRICTION_DIRECTIONS ; .... g...
by bram
Fri Nov 23, 2018 10:12 pm
Forum: General Bullet Physics Support and Feedback
Topic: Generating Contact Constraints.
Replies: 6
Views: 665

Re: Generating Contact Constraints.

Thanks Erwin, Going with gContactProcessedCallback for now. I noticed that my gContactStartedCallback was never called though? So I used gContactProcessedCallback, which does get called. When setting m_appliedImpulseLaterial1 and m_appliedImpulseLateral2 to 0.0, I expected the tyre to slide friction...