Search found 19 matches

by Chaster
Tue Mar 25, 2008 4:37 pm
Forum: General Bullet Physics Support and Feedback
Topic: Need advice - which kind of constraint?
Replies: 4
Views: 3049

Re: Need advice - which kind of constraint?

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 ...
by Chaster
Mon Mar 24, 2008 3:34 am
Forum: General Bullet Physics Support and Feedback
Topic: Need advice - which kind of constraint?
Replies: 4
Views: 3049

Re: Need advice - which kind of constraint?

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...
by Chaster
Sat Mar 22, 2008 4:27 am
Forum: General Bullet Physics Support and Feedback
Topic: Need advice - which kind of constraint?
Replies: 4
Views: 3049

Need advice - which kind of constraint?

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...
by Chaster
Fri Dec 21, 2007 8:34 am
Forum: General Bullet Physics Support and Feedback
Topic: erase static flag from kinematic bodies
Replies: 3
Views: 3370

Re: erase static flag from kinematic bodies

I have never tried to collide a static & kinematic body. You will need to change the collision group AND collision filter flags I think. .
by Chaster
Sat Dec 15, 2007 9:05 pm
Forum: General Bullet Physics Support and Feedback
Topic: erase static flag from kinematic bodies
Replies: 3
Views: 3370

Re: erase static flag from kinematic bodies

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 should ch...
by Chaster
Thu Oct 18, 2007 6:05 am
Forum: General Bullet Physics Support and Feedback
Topic: Changing CollisionGroup & collisionMask... [solved]
Replies: 2
Views: 2021

Re: Changing CollisionGroup & collisionMask... [solved]

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
by Chaster
Wed Oct 17, 2007 7:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: Changing CollisionGroup & collisionMask... [solved]
Replies: 2
Views: 2021

Changing CollisionGroup & collisionMask... [solved]

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 to do...
by Chaster
Tue Oct 16, 2007 1:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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...
by Chaster
Mon Oct 15, 2007 11:17 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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...
by Chaster
Mon Oct 15, 2007 6:07 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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
by Chaster
Mon Oct 15, 2007 5:59 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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...
by Chaster
Mon Oct 15, 2007 5:43 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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...
by Chaster
Mon Oct 15, 2007 5:26 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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...
by Chaster
Mon Oct 15, 2007 5:24 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

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
by Chaster
Mon Oct 15, 2007 5:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: Kinematic bodies with friction applied to dynamic bodies?
Replies: 12
Views: 13949

Re: Kinematic bodies with friction applied to dynamic bodies?

*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