Search found 71 matches

by Ehsanizadi
Sat Apr 18, 2015 10:45 am
Forum: General Bullet Physics Support and Feedback
Topic: btCompoundShape: collision detection problem! :?:
Replies: 10
Views: 2776

Re: btCompoundShape: collision detection problem! :?:

Yes,
Thanks for the help.
So this is "SOLVED" completely.
by Ehsanizadi
Fri Apr 17, 2015 12:51 pm
Forum: General Bullet Physics Support and Feedback
Topic: btCompoundShape: collision detection problem! :?:
Replies: 10
Views: 2776

Re: btCompoundShape: collision detection problem! :?:

Its not related to the world bounds. I just found the source of problem. It is programming glitch rather than a Bullet-related one! When I do "compoundShape->addChildShape(relTransform, childShape);" inside a "for" loop in c++, it will remain valid within that loop, not outside! If I remove that for...
by Ehsanizadi
Fri Apr 17, 2015 10:54 am
Forum: General Bullet Physics Support and Feedback
Topic: btCompoundShape: collision detection problem! :?:
Replies: 10
Views: 2776

Re: btCompoundShape: collision detection problem! :?:

Yes, if I add the compound shape after all of the bodies, only the bottom plate will be recognized. As a result, if a small dynamic body falls into the box, it will be settled on the bottom plane of the empty box, However, in the case you apply a central force in horizontal direction, it will goes f...
by Ehsanizadi
Thu Apr 16, 2015 10:27 am
Forum: General Bullet Physics Support and Feedback
Topic: btCompoundShape: collision detection problem! :?:
Replies: 10
Views: 2776

Re: btCompoundShape: collision detection problem! :?:

Thanks for the hints: 1) the first suggestion for my case is not possible, because I have another compound shape which is dynamic object. 2) updating singleAABBs did not solve the problem, they still pass through eachother 3) I already activated them by : rigidbody->setActivationState(4); 4) Tried, ...
by Ehsanizadi
Wed Apr 15, 2015 8:22 am
Forum: General Bullet Physics Support and Feedback
Topic: Objects randomly drop through ground
Replies: 2
Views: 1232

Re: Objects randomly drop through ground

Hey Ed, As far I understood, in Bullet if dynamic objects are not moved or collided for some time, they will sleep (i.e. they will set to non-dynamic due to some optimization reasons) by the command below you can set your objects in the scene always awake. yourRigidBody->setActivationState(4); Do th...
by Ehsanizadi
Tue Apr 14, 2015 2:50 pm
Forum: General Bullet Physics Support and Feedback
Topic: btCompoundShape: collision detection problem! :?:
Replies: 10
Views: 2776

btCompoundShape: collision detection problem! :?:

Hey all, I have made an example of a empty box using btCompoundShape (out of 5 btBoxShapes) and I made it static object. Then I added a btBoxShape (lets call it falling box) inside the empty box (with some margin, so that the falling box can fall inside the empty box and hit its bottom). However, I ...
by Ehsanizadi
Wed Oct 22, 2014 6:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Friction coefficient using tilt plane
Replies: 5
Views: 2571

Re: Friction coefficient using tilt plane

Even changing time step, iteration number (which is the main parameter for accuracy of phsysics), and also frames per second, all did not have any effect. Based on the coulomb friction law, whcih bullet uses, mass does not affect the friction ration at sliding threshold. If it does, it will be stran...
by Ehsanizadi
Wed Oct 22, 2014 2:28 pm
Forum: General Bullet Physics Support and Feedback
Topic: Friction coefficient using tilt plane
Replies: 5
Views: 2571

Re: Friction coefficient using tilt plane

Thanks for your reply. Actually, I already used a flattend block. Because if I'd have used a block with "height-to-width" ratio of considerable, overturning moments would incluence the results. As you said, I played with the height of the blocks, but still there is no change in the results! I am not...
by Ehsanizadi
Tue Oct 21, 2014 9:33 am
Forum: General Bullet Physics Support and Feedback
Topic: Friction coefficient using tilt plane
Replies: 5
Views: 2571

Friction coefficient using tilt plane

Hey all, I put a cuboid block on a plane and tilted the plane very slowly (about half degree in 10 seconds) to see at which angle of inclination the block will slide. I did the test for various friction coefficients for the contact between block and the plane. As a physical rule, the input friction ...
by Ehsanizadi
Thu Jul 10, 2014 1:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 9431

Re: Spring daming in bullet

Thanks for your responses, Actually what I am looking for, is the calculation loop (based on the Bullet code) for springs. For example in which files I can track the calculation loops of the springs. What I am going to do is to compare the behaviour of hard constraint based springs with soft constra...
by Ehsanizadi
Tue Jul 08, 2014 3:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 9431

Re: Spring daming in bullet

I assume Bullet uses some kind of soft constraint to model springs. Maybe this explanation in the ODE gives you an idea: http://www.ode.org/ode-latest-userguide.html#sec_3_8_0 Erin Catto gave a presentation about soft constraints here: https://box2d.googlecode.com/files/GDC2011_Catto_Erin_Soft_Cons...
by Ehsanizadi
Wed Jul 02, 2014 1:38 pm
Forum: General Bullet Physics Support and Feedback
Topic: Spring daming in bullet
Replies: 10
Views: 9431

Spring daming in bullet

Hi, Does anyone know what formula bullet use for application of damping to an spring? And what is the unit of damping paramter? or is it dimensionless? (the range of damping is between 0 and 1). I tried to look at the source code in "btGeneric6DofSpringConstraint.cpp", however, I couldnt understand ...
by Ehsanizadi
Wed May 07, 2014 2:22 pm
Forum: General Bullet Physics Support and Feedback
Topic: Monitoring forces between rigid bodies
Replies: 3
Views: 2739

Re: Monitoring forces between rigid bodies

m_totalForce is an internal variable used to calculate how much force is accumulated in one stepping, and therefore is set to zero once you call stepsimulation(). If you want to find out the total force at the end of each step, you'll need to add a function for that directly into the solver code (j...
by Ehsanizadi
Wed May 07, 2014 1:10 pm
Forum: General Bullet Physics Support and Feedback
Topic: Wrong fall height calculation
Replies: 4
Views: 2611

Re: Wrong fall height calculation

Thanks Basroil! About question 1: I've just started Bullet, and I just saw the time tuning can be done in stepSimulation() function. So if I use "stepSimulation(1,0)", it means that at every step, simulation will go 1 second forward and without any internal stepping (since the second parameter is se...