Real-Time Physics Simulation Forum

Ahh, it hadn't occurred to me to use two coincident constraints. Although in my case, since I am calling applyTorqueImpulse() directly instead of using a motor to set the velocity, I think I only need one. And also there is m_maxLimitForce (recently introduced?) so you might not need to use the moto...

I'm trying to model a servo which has a lot of gear friction. So the joint is fairly stiff, you have to apply some minimal force before it will move, and then it will seize quickly when you stop. If I model the servo simply by doing my PID loop and testing to see if it exceeds the minimal torque to ...

I'm wondering if someone could give a shot at documenting the btContactSolverInfoData fields. These seem like some critical parameters, but I'm not sure what a lot of them do... for instance I discovered I could fix issues with constraints "breaking" by increasing m_numIterations to around...

I'm not sure I understand the rationale of this patch: http://code.google.com/p/bullet/source/detail?spec=svn2064&r=1984 which added the INSTALL_LIBS option. As far as I know, nothing is installed unless you do a 'make install' (or similar depending on environment). So I'm not sure what the poin...

I'm starting to think this would be easier if the appendages have mass after all, and just the root body be static... or maybe not even that. What I'm really trying to do here is simulate a legged robot. In the "normal" mode, everything has mass and is a dynamic object, so the legs can sli...

I have a set of connected static objects which need to change configuration during execution. Previously these were all grouped as a single compound shape. If I want to smoothly reconfigure the components, should I approach this as modifying the compound shape, or should I divide the pieces into sep...

I rolled back my code to an old version and still seeing this, so I'm thinking it's something else... might be something introduced between 2.74 and 2.75, or something related to Snow Leopard...

I'd like to track this down, but a few suggestions where to start looking would help.

I'm having trouble with an occasional crash in calculateSimulationIslands: #0 0x004a9121 in btUnionFind::find (this=0x204dd54, x=1818322290) at btUnionFind.h:104 #1 0x004a9150 in btUnionFind::unite (this=0x204dd54, p=-1, q=4) at btUnionFind.h:80 #2 0x00611776 in btDiscreteDynamicsWorld::calculateSim...

I was going to say, I wonder if you could add a hook before each timestep set the velocity of your conveyor belt and reset its position back to the starting position, but I think the contacts of objects sitting on the belt might get confused. Which leads to a better suggestion, if you hook into the ...

A first video of using physics in our robot simulator ("Mirage"). http://www.youtube.com/watch?v=wh0t3GtkWGc Mobile robots coming soon, this was the easiest to get started. Bullet interface part of the code is here: http://cvs.tekkotsu.org/viewvc/Tekkotsu/Planners/Dynamics/ The simulator-s...

The color change indicates that the body has "deactivated", which happens when it hasn't moved for a while. This speeds up the simulation because then bullet can stop checking to see if it's going to change in the future. I don't know about the graphics code if you just want to disable the...

(Is there a way to set/increase m_numPerturbationIterations or m_minimumPointsPerturbationThreshold as referenced in the thread above?) Ah, I discovered btDefaultCollisionConfiguration::setConvexConvexMultipointIterations(), but it turns out requesting 3,3 (before constructing btCollisionDispatcher...

I think I'm running into a variation of this post: http://bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=3858 I have a small box with strong gravity. At "standard" gravity of 9.8, the box is a cube, 0.03 on a side. I know this is small and would have trouble with various parameter...

For reference, I've experimented a bit with adding an integrative controller component to the constraint, which will ramp up constraint force to overcome constant inputs like gravity. This allows a smaller ERP to reduce jitter but still retain constraint rigidity, although my naïve initial solution ...

Indeed, switching to btGeneric6DofConstraint fixes the problem. All joints sag evenly now, and I can adjust the m_ERP/m_restitution parameters in the RotationalLimitMotor/TranslationalLimitMotor respectively to tighten that up to my preference (I'm using 0.95, doesn't seem to cause much (additional)...