## Search found 20 matches

Fri Feb 12, 2021 11:24 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Solved]If I want hard constraints is featherstone and multibody the only effective solution?
Replies: 5
Views: 2797

### Re: [Solved]If I want hard constraints is featherstone and multibody the only effective solution?

And here's a quick video showing a well-behaved rag doll, where rigid body min dims are greater the 0.2.

Thanks.
Tue Feb 09, 2021 2:43 pm
Forum: General Bullet Physics Support and Feedback
Topic: Elastic Constraints
Replies: 3
Views: 2678

### Re: Elastic Constraints

Are all of your constrained object dimensions > 0.2 units?
Are you introducing very large position deltas from one sim step to the next?
Sun Feb 07, 2021 11:59 am
Forum: General Bullet Physics Support and Feedback
Topic: Simulate the dynamics in large particle systems on which external forces acts with elastic collisions in real time
Replies: 4
Views: 1908

### Re: Simulate the dynamics in large particle systems on which external forces acts with elastic collisions in real time

If you can restrict things to sphere/sphere interactions, the collision detection is as simple as it gets: sum of radii squared <= dist between centres squared is a collision. Penetration depth and recovery normal are equally trivial to calculate. Assuming you have a modern graphics card supporting ...
Sun Feb 07, 2021 11:23 am
Forum: General Bullet Physics Support and Feedback
Topic: [Solved]If I want hard constraints is featherstone and multibody the only effective solution?
Replies: 5
Views: 2797

### Re: [Solved]If I want hard constraints is featherstone and multibody the only effective solution?

Apologies for not replying sooner. I missed your responses. The good news from my perspective, is that having integrated but not used a multi body loader, I got a well behaving skeleton set up using only the default sequential impulse solver. How did I do this? By following the rules on world scalin...
Wed Nov 11, 2020 8:05 pm
Forum: General Bullet Physics Support and Feedback
Topic: [Solved]If I want hard constraints is featherstone and multibody the only effective solution?
Replies: 5
Views: 2797

### [Solved]If I want hard constraints is featherstone and multibody the only effective solution?

Hi, For context, I don't use the python binding and only use the core Dynamic, Collision and LinearMaths libraries in my code. I've had a rag doll implementation, using the sequential impulse solver for years and ignored the "elasticity" in the constraint chains. I've read most posts relat...
Thu Oct 15, 2020 11:50 pm
Forum: General Bullet Physics Support and Feedback
Topic: After 15 years of people asking - Why is Bullet documentation still so very bad?
Replies: 2
Views: 1441

### Re: After 15 years of people asking - Why is Bullet documentation still so very bad?

Fair comment, I hadn't really considered the driving force being academic research and the implications therein. I'd assumed it was more a labour of love on the part of the primary author and others. I'm not saying it isn't both of course. It's a pity that knowledge is being repeatedly gained and lo...
Sat Oct 10, 2020 8:03 pm
Forum: General Bullet Physics Support and Feedback
Topic: After 15 years of people asking - Why is Bullet documentation still so very bad?
Replies: 2
Views: 1441

### After 15 years of people asking - Why is Bullet documentation still so very bad?

Apologies, for the deliberately provocative subject but I doubt I'm the only person to wonder this after years of usage. Bullet is 15+ years old A wiki was started, but is no longer available and seems not worthy of resurrection The user manual is good but is really an overview When people ask quest...
Sat Aug 25, 2018 8:49 pm
Forum: General Bullet Physics Support and Feedback
Topic: Improving collision detection/response for rag dolls
Replies: 6
Views: 5667

### Re: Improving collision detection/response for rag dolls

I finally managed to fully resolve the issues described above and collision response between chains of constrained bodies, including rag dolls and BVH Tri-meshes are now error-free. The solution was two-fold, with the first step being embarrassingly obvious: 1) I was using v2.82 rather than the late...
Sat Aug 25, 2018 5:47 pm
Forum: General Bullet Physics Support and Feedback
Topic: Ragdoll body parts fall through ground
Replies: 4
Views: 3646

### Re: Ragdoll body parts fall through ground

For anyone searching for solutions to similar trimesh / ragdoll / constraint chain penetration problems, I was able to resolve my problems fully.
I've updated my original post with an explanation:
https://pybullet.org/Bullet/phpBB3/view ... =9&t=11481
Wed Nov 29, 2017 9:06 pm
Forum: General Bullet Physics Support and Feedback
Topic: Collision with large terrain
Replies: 3
Views: 3146

### Re: Collision with large terrain

To answer the first poster and the third: Use btBvhTriangleMeshShape for terrain that requires overhangs, tunnels etc. Trimeshes require geometry data that consists of vertices and triangle indices and are necessarily more complex input data. That said, tools like Blender export in lots of formats l...
Mon Nov 06, 2017 10:30 pm
Forum: General Bullet Physics Support and Feedback
Topic: Ragdoll body parts fall through ground
Replies: 4
Views: 3646

### Re: Ragdoll body parts fall through ground

I have a similar unresolved problem with any simple chain of rigid bodies and bad interpenetration with bhv tri meshes. CCD has not resolved the issues and I have to increase the sub-steps too high to be a practical solution in a game engine. My assumption is that the non-solid nature of the tri mes...
Thu Aug 24, 2017 8:00 pm
Forum: General Bullet Physics Support and Feedback
Topic: Improving collision detection/response for rag dolls
Replies: 6
Views: 5667

### Re: Improving collision detection/response for rag dolls

Long time since your question re. Setting up CCD but just in case you check back: I set up CCD as per the user manual, i.e. just call the 2 functions detailed above on a specific rigid body instance. As far as I'm aware that's all that is required. For anyone who's interested, I never resolved this ...
Sat Jan 14, 2017 7:34 pm
Forum: General Bullet Physics Support and Feedback
Topic: Improving collision detection/response for rag dolls
Replies: 6
Views: 5667

### Re: Improving collision detection/response for rag dolls

For anyone who is interested, implementing per rigid body CCD, has not improved the interpenetration issues I'm experiencing. I have set up CCD on each of the RBs in a 3 RB/2 hinge constraint chain, so RB + hinge + RB + hinge + RB. Each RB has a capsule as its collision shape. I have also set the sw...
Mon Jan 09, 2017 9:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Improving collision detection/response for rag dolls
Replies: 6
Views: 5667

### Re: Improving collision detection/response for rag dolls

Thanks for taking the time to reply. It's much appreciated. The scaling advice is a good pointer, although my rigid bodies are around the 0.5 to 2 unit size, which I believe conforms to the "good practice" pointers found in the bullet manual. That said, my test landscape mesh does have com...
Sun Jan 08, 2017 5:11 pm
Forum: General Bullet Physics Support and Feedback
Topic: Improving collision detection/response for rag dolls
Replies: 6
Views: 5667

### Improving collision detection/response for rag dolls

Hi, I have skeletal mesh animation and the transition to bullet-controlled rag doll animation working and now want to improve the collision detection/response between the rag doll's rigid bodies and the static world mesh. For simple test purposes, I have a chain of 3 rigid body capsules, with 2 ball...