Real-Time Physics Simulation Forum

Well, I do admit that my situation is fairly unique in that I have many characters running around an environment which is itself moving (people inside a large ship) and the characters are often jumping, being pushed around by the environment, etc. The modifications necessary to handle these complex ...

I see that the Bullet maintainers propose using a kinematic body for a single character, and I can see how that would be easier for a single character, but I wonder - how will the kinematic character react when bumping into other characters? In other words, if you have a lot of characters moving aro...

Hello Bullet Folks, I'm working on a game using Bullet (and Ogre) and it's coming along fairly well, but the issue of character control is rearing it's ugly head. Currently, I have a system which works, but is not quite good enough. (before you ask, yes, I looked at the character control demo in the...

I have never tried to collide a static & kinematic body. You will need to change the collision group AND collision filter flags I think. .

I have noticed the same thing (making a body kinematic by changing the collision flags to include CF_KINEMATIC does not remove the CF_STATIC flag) and thought it odd. However, it does work for me. Apparently, kinematic bodies are "special case" versions of static bodies. One thing that you...

Ah, thank you for the tip Erwin. I was just about to post a question about why sometimes the collisionGroup and CollisionMask was used correctly, and sometimes not, but you just answered it.

Many thanks,

Eric

Hello everyone, I'm still trying to get a handle on Bullet, but it's coming along... I have a question - how can I change the collisionGroup & collisionMask filters AFTER a collision object has been added to a simulation world? I know how to do it via addCollisionObject() but was wondering how t...

Hi Ola, Thanks! That's a very smart (obvious) thing to do. Of course, last night I found out that my REAL problems were: 1) OgreBullet (interface library I am using which sits between Ogre3D and Bullet) was using SimpleDynamicsWorld for simulation (Doh!). Fixed. 2) I was passing in milliseconds inst...

Update: After a LOT of testing/tweaking/exploring I think I found the problem. My stepSimulation call is being called with timeDelta = 1/frame rate, maxSubSteps = 1. The kinematic object had it's rotation being updated according to frameRate (which varies anywhere from 80fps to 200fps). When I updat...

Update: I modified the CCDApp demo to rotate instead of move linearly, and it works as expected (although not perfect, it's pretty good). The problem in my app is either something in my code or perhaps the inaccuracy is prominent because of the scale of the objects maybe... Thanks again Erwin, Chaster

The collision shape for the dynamic body is a cube. Although cones exhibit the same behavior. I am looking at the CCDPhysics demo right now with USE_KINEMATIC_GROUND 1 defined, and I see that the stack of cylinders is moving horizontally with the ground, but I don't see a rotational element to the m...

Thanks for taking the time to reply Erwin. Really appreciate it. I am currently compiling 2.63 to compare with what is going on in my simulation. I am glad that it should work - that narrows it down to something I am doing wrong (not surprising since I am new to Bullet). I will report back with what...

This should just work. Can you check out a working example in the CcdPhysicsDemo: enable at the top of CcdPhysicsDemo.cpp the define #define USE_KINEMATIC_GROUND 1 The floor kinematically moves, and stack of cylinders moves with it due to friction. Make sure you are setting these properties for the...

Update:

Okay, more testing reveals that linear motion seems to impart friction (although not quite sure how accurate) but angular motion of the kinematic body imparts very little (if any) friction force to the rigid body sitting on the kinematic body.

Is this a bug?

Chaster

*ping*... Anybody have any input on the proper way to handle this? (imparting friction from kinematic moving bodies to dynamic rigid bodies properly)? A hint perhaps? Or am I just trying to do something which isn't really possible?

Chaster