Search found 96 matches
- Thu Aug 06, 2009 2:30 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: timesteps
- Replies: 3
- Views: 5177
Re: timesteps
For objects to settle/balance properly, the simulation needs to move them for the same amount of time in each update cycle ("step"). Otherwise, if you had a variable timestep, if an object is oscillating slightly, it might move further on one side of the oscillation with a larger timestep,...
- Wed Aug 05, 2009 7:27 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: "Broken" hinge constraint [SOLVED]
- Replies: 6
- Views: 7177
Re: "Broken" constraint
It's interesting that the sag of each joint only depends on the CoM of the immediately following link, not all attached links on the arm... Actually, I take this back, modifying the weight of the last link affects the sag of all of the links leading up to it. So things seem "sane", it's j...
- Wed Aug 05, 2009 7:12 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: "Broken" hinge constraint [SOLVED]
- Replies: 6
- Views: 7177
Re: "Broken" constraint
OK, some more data points: this is directly related to the gravity and center of mass of the immediately following link, but not to the total mass or CoM of subsequent links. So in other words, in the previous screen shots, the CoM of each link was at the hinge, but as I move the CoM out along the l...
- Wed Aug 05, 2009 6:16 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: servo implementation tips?
- Replies: 3
- Views: 6143
Re: servo implementation tips?
There are motors implemented in several constraints (6DOF etc), those are recommended over directly applying impulses. Yeah, I've played with that as well. I might switch over to it since it takes the object mass/inertia into account so I don't have to tweak my controller parameters for each object...
- Wed Aug 05, 2009 6:04 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: "Broken" hinge constraint [SOLVED]
- Replies: 6
- Views: 7177
"Broken" hinge constraint [SOLVED]
I have a planar arm, i.e. a series of bodies connected with parallel hinge joints. However the middle hinge "breaks" and dangles instead of staying rigid. http://img43.imageshack.us/img43/8726/picture2gac.th.png The masses are 0.2 for each link, the base is mass 0 to keep it in the air. Th...
- Wed Aug 05, 2009 5:37 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: servo implementation tips?
- Replies: 3
- Views: 6143
Re: servo implementation tips?
*bump* I'm still interested in a response.
I've gotten things basically working by just using applyTorqueImpulse, but is there a better way? Should there be a version of applyTorquImpulse which takes a location as well as axis?
I've gotten things basically working by just using applyTorqueImpulse, but is there a better way? Should there be a version of applyTorquImpulse which takes a location as well as axis?
- Wed Aug 05, 2009 5:26 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Direct manipulation of Rigid Bodies
- Replies: 3
- Views: 4110
Re: Direct manipulation of Rigid Bodies
See also my other recent threads:
http://bulletphysics.com/Bullet/phpBB3/ ... f=9&t=3315
http://bulletphysics.com/Bullet/phpBB3/ ... f=9&t=3895
where I'm also waiting for implementation tips on a similar problems (how best to apply forces in the world)
http://bulletphysics.com/Bullet/phpBB3/ ... f=9&t=3315
http://bulletphysics.com/Bullet/phpBB3/ ... f=9&t=3895
where I'm also waiting for implementation tips on a similar problems (how best to apply forces in the world)
- Wed Aug 05, 2009 5:23 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Direct manipulation of Rigid Bodies
- Replies: 3
- Views: 4110
Re: Direct manipulation of Rigid Bodies
I think you need to keep Bullet in the loop if you want the objects to interact in a physical way. Think about it in terms of what happens in the "real world" when you grab an object and move it around: you apply more or less force depending how quickly you try to move and the weight of th...
- Wed Aug 05, 2009 5:03 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: timesteps
- Replies: 3
- Views: 5177
Re: timesteps
But there is the possibility to set time steps in the class btDiscreteDynamicsWorld with the function stepSimulation(...). 1) What is it used for? Internal step size, so you call periodically based on your graphics framerate (which might be variable) and have the simulation do a number of internal ...
- Wed Aug 05, 2009 4:52 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Simulating dominoes
- Replies: 1
- Views: 3184
Re: Simulating dominoes
I wonder if you look at contiguous chunks of N dominoes, and they're all deactivated, then replace them with a compound shape and a single body. Then if something wakes up the body, replace it with the original individual dominoes. This could even be done recursively, so it will scale well. I'm a ne...
- Sat Aug 01, 2009 12:20 am
- Forum: General Bullet Physics Support and Feedback
- Topic: servo implementation tips?
- Replies: 3
- Views: 6143
servo implementation tips?
I want to implement a PID (and/or just proportional) motor controller to simulate the servos on a robot. Looking at how the motor on the hinge constraint is implemented, it seems I should just call applyTorqueImpulse on each of the connected bodies for each simulation step. However, I feel I am miss...
- Fri Jul 31, 2009 6:16 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: applyForce() / applyCentralForce() ignored in tick callback?
- Replies: 7
- Views: 11655
Re: applyForce() / applyCentralForce() ignored in tick callback?
So, what is the current advice for what should be called from a dynamics world tic callback? btHingeContraint.h has the following documentation for setMotorTarget: // extra motor API, including ability to set a target rotation (as opposed to angular velocity) // note: setMotorTarget sets angular vel...
- Fri Jul 31, 2009 3:53 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: btBoxShape collision oddity (with video) [SOLVED]
- Replies: 3
- Views: 4491
Re: btBoxShape collision oddity (with video) [SOLVED]
For reference of those who come later, related threads: http://www.bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=1150 http://www.bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=2428 http://www.bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=2513 semi-related: http://www.bul...
- Fri Jul 31, 2009 3:42 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: porting from bullet 2.71 to 2.74: Friction Callback gone
- Replies: 14
- Views: 17073
Re: porting from bullet 2.71 to 2.74: Friction Callback gone
BTW, "Custom Friction Model" is still mentioned in the user manual, although as reported here, the SetFrictionSolverFunc() that CcdPhysicsDemo (referenced from the manual) depended on has been removed. Might be nice to take a second and remove the outdated code from the demo and give a lit...
- Thu Jul 30, 2009 8:23 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: btBoxShape collision oddity (with video) [SOLVED]
- Replies: 3
- Views: 4491
Re: btBoxShape collision oddity (with video)
I have discovered my problem, but I'm not sure *why* it's a problem: I was doing this: dynamicsWorld->addRigidBody(body); body->setWorldTransform(tr); However, if I swap these: body->setWorldTransform(tr); dynamicsWorld->addRigidBody(body); Then everything is happy. The order does not matter if the ...