Search found 85 matches

by DannyChapman
Tue Oct 16, 2018 3:05 pm
Forum: General Bullet Physics Support and Feedback
Topic: Strange behavior of rigid bodies (video) C++
Replies: 7
Views: 599

Re: Strange behavior of rigid bodies (video) C++

Looks like your multiplication order is the wrong way round
by DannyChapman
Mon Oct 15, 2018 9:36 pm
Forum: General Bullet Physics Support and Feedback
Topic: Strange behavior of rigid bodies (video) C++
Replies: 7
Views: 599

Re: Strange behavior of rigid bodies (video) C++

You didn't respond to my suggestion to check your maths. The best ways to do that are to 1. Look at it and check that your code matches what you wrote down on paper 2. Feed it simple input, and check that the output is what you expect. In this case, the output of your maths is a rendered object, and...
by DannyChapman
Sat Oct 13, 2018 12:21 pm
Forum: General Bullet Physics Support and Feedback
Topic: Strange behavior of rigid bodies (video) C++
Replies: 7
Views: 599

Re: Strange behavior of rigid bodies (video) C++

Just from the video - it looks like you're rendering your shapes offset (a long way) sideways from the actual physical objects. That would explain why initially they look OK when they fall - the real stack would be some distance to the side. But when the objects start falling and rotating, your rend...
by DannyChapman
Tue Jul 31, 2018 4:25 pm
Forum: General Bullet Physics Support and Feedback
Topic: btHeightfieldTerrainShape going nuts
Replies: 8
Views: 2645

Re: btHeightfieldTerrainShape going nuts

It's odd looking at this old code again! You can set the contact added callback from btManifoldResult.cpp: ContactAddedCallback gContactAddedCallback=0; I set mine to this: //---------------------------------------------------------------------------------------------------------------------- bool C...
by DannyChapman
Thu Oct 19, 2017 11:43 pm
Forum: General Bullet Physics Support and Feedback
Topic: Vs2015 Build failure - unicode problems
Replies: 1
Views: 958

Re: Vs2015 Build failure - unicode problems

In addition - the make system makes the projects have the debug and release libs have the same name! Consequently you'll get all sorts of linker errors. So far my success at building and linking against Bullet comes from: 1. Changing the build_*.bat scripts to use vs2015 rather than vs2010 (because ...
by DannyChapman
Wed Oct 18, 2017 9:22 pm
Forum: General Bullet Physics Support and Feedback
Topic: Vs2015 Build failure - unicode problems
Replies: 1
Views: 958

Vs2015 Build failure - unicode problems

I've download bullet3-2.87.zip ready to use it in a new project, run build_visual_studio_without_pybullet_vr.bat, open the build3/vs2010/0_Bullet3Solution.sln in Visual Studio 2015 (Update 3). If I just compile, I hit things like this: 10>..\..\examples\SharedMemory\b3PluginManager.cpp(117): error C...
by DannyChapman
Thu Mar 23, 2017 11:50 am
Forum: General Bullet Physics Support and Feedback
Topic: Mass not effecting dynamic rigid bodies?
Replies: 8
Views: 2366

Re: Mass not effecting dynamic rigid bodies?

If you want heavy objects to fall (accelerate) faster than light ones, you have to ask yourself why. The most likely answer is that the objects are affected by drag (air resistance) too - in which case rather than hacking gravity, it's probably better to add a drag force. This will give more realist...
by DannyChapman
Tue Feb 21, 2017 11:06 pm
Forum: Release Announcements
Topic: Bullet 2.83 released on github: Example Browser, URDF
Replies: 8
Views: 54522

Re: Bullet 2.83 released on github

The feature to include the gyro terms in the solver is excellent - it turns out to be really important for correct simulation of aircraft spins and snap rolls etc, so much appreciated. I'll post a video of it in my R/C flight sim shortly. Thanks - Danny Have you posted your video already? If yes, w...
by DannyChapman
Thu Feb 09, 2017 4:04 pm
Forum: General Bullet Physics Support and Feedback
Topic: Fixing "Hopping" - Rolling Sphere Collision
Replies: 4
Views: 1585

Re: Fixing "Hopping" - Rolling Sphere Collision

This can (will) happen if the ball hits internal edges in the surface it's rolling on. Difficult to tell from the video if that's the case as we'd need to see the collision shapes. Certainly if you have two boxes, A and B, next to each other with their top surfaces in the same plane, then as a ball ...
by DannyChapman
Wed Sep 21, 2016 3:43 pm
Forum: General Bullet Physics Support and Feedback
Topic: Table Robot Legs Positions
Replies: 5
Views: 2785

Re: Table Robot Legs Positions

Bullet uses an iterative solver, so the degree to which it converges depends on the timestep and the number of solver iterations. Decreasing the former and increasing the latter normally helps. You could also look at the btMultiBody object, which implements a Featherstone solver. I'm not sure if tha...
by DannyChapman
Wed Sep 21, 2016 3:27 pm
Forum: General Bullet Physics Support and Feedback
Topic: btHeightfieldTerrainShape going nuts
Replies: 8
Views: 2645

Re: btHeightfieldTerrainShape going nuts

Could they be hitting the internal edges? This can happen even if the terrain is completely flat, due to the way that the collision checks are done against the individual triangles. This started causing big problems for me, after putting up with it for a long time. You can see the problem here: http...
by DannyChapman
Wed Aug 17, 2016 11:35 pm
Forum: General Bullet Physics Support and Feedback
Topic: SoftBody behaviour with time increment and iteration number
Replies: 3
Views: 1988

Re: SoftBody behaviour with time increment and iteration num

Hi all, However, I found out that soft body (not even ropes, but patches) behave strangely with time step and iteration! Yes, I get this - my simulation timestep can vary a lot, and that causes problems because the accuracy of the rope simulation varies. I don't mind a bit of stretching (actually f...
by DannyChapman
Sat Mar 19, 2016 10:19 pm
Forum: General Bullet Physics Support and Feedback
Topic: Directional Friction
Replies: 5
Views: 1483

Re: Directional Friction

What's wrong with the btCollisionObject::setAnisotropicFriction function?!
by DannyChapman
Sat Feb 13, 2016 11:08 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Lightweight engine for simulating dice?
Replies: 4
Views: 3443

Re: Lightweight engine for simulating dice?

If you only want one die, on a plane for the floor, and a couple of planes for the walls, you can "roll your own" (ha ha - sorry!) using the verlet stick-and-particle method (though getting decent friction is always a pain with that). If you want any more than that, using Bullet (what platform are y...
by DannyChapman
Mon Jan 04, 2016 8:33 pm
Forum: General Bullet Physics Support and Feedback
Topic: Friction: what is the unit?
Replies: 5
Views: 2578

Re: Friction: what is the unit?

Friction has no unit of measure; it is a dimensionless coefficient . Just think of it as a dial that twist from 0 (frictionless) to 1 (max friction). It is indeed dimensionless, but there's no upper limit. The friction value that you set on a rigid body object in Bullet isn't a "real" physical prop...