Search found 10 matches

by bteitler
Wed Jan 22, 2014 5:55 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

Hmm, the hinged door solution with local inertia set to 0 for two of the axes doesn't seem to play nice with with static objects. The door simply rotates through the static objects instead of "blocking" the rotation as I'd expect.
by bteitler
Sat Jan 18, 2014 11:19 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

I didn't know about the inertia settings. Seems to be exactly what I needed. I tested it, and combined with the custom gravity per tick, this seems to perform pretty realistically. This should meet my requirements I think. Thanks for your help.
by bteitler
Fri Jan 17, 2014 10:26 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

Hmm.. well I'll read up on the stability issues. Regarding the rigid door issue, I was able to get something that works more or less like what I want while respecting gravity as well, but only for axis aligned doors. I start with a box with center of mass at an edge (for hinge), and set linear facto...
by bteitler
Thu Jan 16, 2014 5:59 pm
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

In a nutshell, the iterative solver doesn't find a good solution when there are multiple constraints (contact, hinge) and bodies with large differences in mass (even 1kg vs 100kg is large). No good solution means that the constraints are still violated at the end, and this can be visible as penetra...
by bteitler
Thu Jan 16, 2014 6:46 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

The iterative constraint solver might not be able to converge to the right solution, especially if the masses of the objects involved are very different. I keep reading this in multiple places and I don't really understand what is meant by it. Is it that larger forces create more instability due to...
by bteitler
Wed Jan 15, 2014 1:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

I tried various tricks like setting linear / angular factors of dynamic bodies with high mass to 0 and attaching a door via constraint. The constraint still wobbles exactly like before unfortunately. So instead I modeled a hinge from a compound body of cylinder + box for the door, with center of mas...
by bteitler
Wed Jan 15, 2014 12:30 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

The paper is interesting but seems to be a more general bench-marking comparison. It might tell me what implementations are more accurate in some aggregate case over random common setups (chuck a bunch of moving objects together), where I basically want to know a very a specific question: Are constr...
by bteitler
Tue Jan 14, 2014 5:33 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

I tried every combination of high/low values of BT_CONSTRAINT_STOP_CFM, BT_CONSTRAINT_ERP, BT_CONSTRAINT_STOP_CFM, and BT_CONSTRAINT_STOP_ERP. It either did something crazy like ignoring my angle constraints, or there was no visible effect (hinge still jiggles all over). I notice that interactions b...
by bteitler
Tue Jan 14, 2014 12:28 am
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Re: Door knocked off hinge constraint by collisions

Hmm.. disappointing to see that this is not a simple task. In my mind, "constraint" means actually constrained... not kind of sort of springy system. I don't think I can use Bullet if I can't get this to work right. I think just fiddling with parameters without a guarantee of rigidity is going to de...
by bteitler
Mon Jan 13, 2014 1:09 pm
Forum: General Bullet Physics Support and Feedback
Topic: Door knocked off hinge constraint by collisions
Replies: 18
Views: 7718

Door knocked off hinge constraint by collisions

I'm new to Bullet, and I'm trying to get a simple door set up. The door should be attached rigidly to the world and swing between 0 and 90 degrees. By "rigid", I mean that the door hinge should not be breakable or bendable by objects that collide with it. I'm using the following constructor for my h...