Real-Time Physics Simulation Forum

Hi, V-REP, the Virtual Robot Experimentation Platform, is a 3D robot simulator, with integrated development environment, based on a distributed control architecture. Its default physics engine is Bullet, but ODE is also supported (for a same simulation, the user can switch from one to the other phys...

Hello, Since quite some time I am using Bullet by scaling dimensions up by a factor 10 (or more) for better stability (I work in smaller dimensions). Of course I accordingly scale up all other values too in a correct fashion. That works fine. However I am not scaling up collision margins (by default...

Hello, I am trying to obtain the force vector of a contact. In a previous post (http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=2568&hilit=contact+info), Erwin suggested to use following: m_appliedImpulse*m_normalWorldOnB/deltaTime This works fine, but doesn't really represent the...

Hello, The Virtual Robot Experimentation Platform (V-REP) was released a few months ago with Bullet as its dynamics module (V-REP is a hybrid simulator with several calculation modules, see below). Since a few days, V-REP is now also supporting the Open Dynamics Engine, and the user can switch from ...

Maybe try to increase the mass of the small rope elements?

Hello, I just finished my first release of the Virtual Robot Experimentation Platform (V-REP). It is a general-type robot simulator. It allows you to edit and simulate whole robotic systems, or sub-systems (sensors, mechanisms). It offers a multitude of functionalities that can be easily integrated ...

Well, I just noticed why the setMargin didn't have an effect: I wrap all collision shapes in a compound shape in order to freely adjust the inertia position/orientation relative to the shape, and I was setting the margin of the compound shape. Setting the margin of the btConeShapeZ to zero works fin...

Hello, I am not sure if this is intended or something that was overlooked but I noticed following about collision margins (version 2.76 R1971: btBoxShape-btBoxShape: 0 cm btCylinderShapeZ-btBoxShape: 0 cm btSphereShape-btBoxShape: 0 cm btConeShapeZ-btBoxShape: 4 cm btCylinderShapeZ-btCylinderShapeZ:...

I tested the btSliderConstraint in r1971, everything seems alright. >>can you explain what adjustments you need to make exactly? Actually I added a few lines in btSequentialImpulseConstraintSolver so that I can extract applied impulses for the btGeneric6DofConstraint (which then allows me to use the...

Hello Erwin, The btSliderConstraint's strange behaviour is resolved in the latest release (v2.76, r1963). About the btGeneric6DoFConstraint: I am using that constraint also as a force/torque sensor, and I noticed that the 6 constraint equations have changed from previous release (v2.75): before, the...

Hello Erwin,

Yes, I just dowloaded the latest source (2.76, r1963) and the problem is fixed, thanks a lot!

Hello, Since Bullet version 2.76, most constraints have a new define added, e.g.: #define USE_OFFSET_FOR_CONSTANT_FRAME true // btSliderConstraint #define D6_USE_FRAME_OFFSET true // btGeneric6DofConstraint #define HINGE_USE_FRAME_OFFSET true // btHingeConstraint I noticed strange behaviours of btSl...

Hello Roman, Actually I realized that since version 2.76, there is a define as following for btSliderConstraint: #define USE_OFFSET_FOR_CONSTANT_FRAME true if I set it to false, then all seems ok. Same with btGeneric6DofConstraint, in version 2.76 it behaves strangely. There is also a similar define...

Thanks roman, Yes, the 2.75 version I used was released on the 17th of September 2009. Here my code for the slider: btSliderConstraint* slider; btTransform jtrA; jtrA.setOrigin(btVector3(jtrRelToBodyA.X(0),jtrRelToBodyA.X(1),jtrRelToBodyA.X(2))); jtrA.setRotation(btQuaternion(jtrRelToBodyA.Q(1),jtrR...

Hello,

I am not sure if this was meant, but since Bullet 2.76, the btSliderConstraint moves along the NEGATIVE x-axis (was the POSITIVE x-axis in Bullet 2.75). I corrected for that by adjusting the frames that I feed to Bullet, but I am now wondering if this change was meant or accidental?