Real-Time Physics Simulation Forum

Hi, I'm using Bullet for an engineering simulation and I need to know the contact forces. Is it possible in Bullet? For example dropping a box on table, can we get the force/impulse induced by the collision between box and table? What about resting objects on each other? For example a box put on the...

Yes,
Thanks for the help.
So this is "SOLVED" completely.

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! ...

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...

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, ...

Any suggestion?

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...

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 ...

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...

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...

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 ...

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...

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...

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 u...

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...