Search found 22 matches

by monkeyman
Wed Aug 08, 2012 11:14 pm
Forum: General Bullet Physics Support and Feedback
Topic: Changing the shape of a rigid body (opening a door in wall)
Replies: 3
Views: 4905

Re: Changing the shape of a rigid body (opening a door in wa

Hi, What would be best practice here? - Remove the RigidBody from the collisionWorld and add a new one when door opens/closes - track it outside the world by reference and somehow manipulate the sub shape (I'm assuming this will need a CompoundShape) Is there some other approach that is better? Usu...
by monkeyman
Mon Aug 06, 2012 1:12 am
Forum: General Bullet Physics Support and Feedback
Topic: Constraints for wheels
Replies: 6
Views: 8727

Re: Constraints for wheels

In your opinion is it possible at all to simulate a vehicle using actual turning cylinders as wheels in Bullet? I thought most people doing vehicle simulations did a hack when modelling wheels, so they seem to spin by the renderer, but in the physics engine they are just collision-detection cylinder...
by monkeyman
Mon Aug 06, 2012 1:08 am
Forum: General Bullet Physics Support and Feedback
Topic: Incorrect ConvexSweepTest LocalConvexResult
Replies: 5
Views: 5264

Re: Incorrect ConvexSweepTest LocalConvexResult

monkeyman: Thanks for the reply. As far as I've found thus far my suspicions were correct, at least its giving me normals correct enough to work with. I've had to change my navigation method for the Controller I'm working on due to the narrow margins of collision i'm working with, which sweeps unti...
by monkeyman
Sat Jul 28, 2012 10:43 pm
Forum: General Bullet Physics Support and Feedback
Topic: ConvexSweepTest Keeps Failing
Replies: 5
Views: 6579

Re: ConvexSweepTest Keeps Failing

As a side-note, the btKinematicCharacterController has the same bug, it updates positions of the character without recalculating the AABBs and hence will miss interpenetrations.. Hello, how you update the ghost object AABBs for the btKinematicCharacterController? Thank you Bruno You need to put som...
by monkeyman
Thu Jul 26, 2012 9:32 pm
Forum: General Bullet Physics Support and Feedback
Topic: Changing postition of a kinematic body and missed collisions
Replies: 5
Views: 5765

Re: Changing postition of a kinematic body and missed collis

The user input device I'm using sends the change in position from the last packet, so the kinematic bodies do not necessarily move in small steps. Fast movement from the user means larger steps from one spot to the next. My theory on this is that it seems like bullet is treating them as though they...
by monkeyman
Thu Jul 26, 2012 8:44 pm
Forum: General Bullet Physics Support and Feedback
Topic: ConvexSweepTest Keeps Failing
Replies: 5
Views: 6579

Re: ConvexSweepTest Keeps Failing

Okay, I solved the issue. Turns out this is a fundamental issue with our implementation of a kinematic bullet environment: updateAABBs needs to be called when anything moves in the world. Normally, this is taken care of inside tick(), but since we are using bullet merely for kinematic collision che...
by monkeyman
Mon Jul 23, 2012 9:41 am
Forum: General Bullet Physics Support and Feedback
Topic: Incorrect ConvexSweepTest LocalConvexResult
Replies: 5
Views: 5264

Re: Incorrect ConvexSweepTest LocalConvexResult

To update, it appears that the ConvexSweep is returning the triangle face normal I was trying to get manually. Broadphase results vs a BVH force you to locate the triangle and calculate the normal yourself, as the normal returned in the manifold is the "Separating" normal in world space. ...
by monkeyman
Thu Feb 23, 2012 11:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: "Sticky" objects
Replies: 1
Views: 3145

Re: "Sticky" objects

i found this behaviour when I ran code within one of the bullet demos which had enabled the continuous collision detection. after an object collided with a compound shape, it could stick there for a second, then move a bit, then stick again, then continue moving... check if you have some of the cont...
by monkeyman
Wed Feb 22, 2012 12:10 am
Forum: General Bullet Physics Support and Feedback
Topic: [Feature request] method to provide collision object index
Replies: 1
Views: 3207

Re: [Feature request] method to provide collision object ind

normally, objects are added and removed all the time to the world, so the actual indices in the internal arrays are not really meaningful... i would say that the user pointer system in this case actually seems like the best way to get your ogre index back. just set the user pointer in the bullet col...
by monkeyman
Wed Feb 01, 2012 10:50 am
Forum: General Bullet Physics Support and Feedback
Topic: best way to make a helicopter?
Replies: 2
Views: 6640

Re: best way to make a helicopter?

Actually the pitch of the blades are varied throughout the rotation by a mount called the swashplate, so the blades can for example develop more lift on the left side of the helicopter than the right. The controls of the heli shift this asymmetry to develop thrust laterally. The pitch can also be va...
by monkeyman
Tue Jan 17, 2012 9:46 am
Forum: General Bullet Physics Support and Feedback
Topic: Bullet 2.77 Restitution issue.
Replies: 8
Views: 11027

Re: Bullet 2.77 Restitution issue.

What it tries to do when penetration is larger than 0 (which is what happens when an object is almost but not quite touching another) is calculate the change in velocity required so that collision occurs exactly on the next time step. But that only works if the restitution speed is zero. When there...
by monkeyman
Mon Jan 16, 2012 8:08 am
Forum: General Bullet Physics Support and Feedback
Topic: SoftBody Bunny Car Demo
Replies: 3
Views: 4404

Re: SoftBody Bunny Car Demo

Thanks, for the reply monkeyman and this is the demo with the bunny going down the staircase. What you have mentioned. That was my first imppresion that the wheels were somehow rubbing against each other Makeing the vehicle unstable. But this is not the case What is Happening is when the Motorcontr...
by monkeyman
Sat Jan 14, 2012 3:23 pm
Forum: General Bullet Physics Support and Feedback
Topic: SoftBody Bunny Car Demo
Replies: 3
Views: 4404

Re: SoftBody Bunny Car Demo

Hello Everyone in The Bunny Car sample when the m or n key is pressed and held down the car pops a wheelie and spins out of control why dose this happen and how can this be fixed I tried Using applyForce on the Vehicle thinking it might apply some downward force to the Vehicle and stop the body fro...
by monkeyman
Tue Jan 10, 2012 10:34 pm
Forum: General Bullet Physics Support and Feedback
Topic: Emulating energy-loss in collisions
Replies: 0
Views: 2501

Emulating energy-loss in collisions

Hi, is there a built-in method in Bullet to emulate inelastic energy-loss in collisions? Lets say I have two concrete blocks colliding, in bullet they will, if hit on say a corner, start to spin wildly, while in real life they would never do that, a collision imparting that amount of impulse would j...
by monkeyman
Mon Jan 09, 2012 12:12 pm
Forum: General Bullet Physics Support and Feedback
Topic: split or merge static geometry before broadphase?
Replies: 0
Views: 2407

split or merge static geometry before broadphase?

Hi, this is in the Bullet wiki: Other Tips For Increasing Broadphase Speed If you have a large amount of static trimesh collision shapes, batch them together using a single btBvhTriangleShape. This will only have one entry in the broadphase. Could someone weigh in with pros and cons here? Since norm...