Real-Time Physics Simulation Forum

Re: Remove Collision from an entire MultiBody

2019-02-26T00:52:30+00:00

Good to hear it is fixed!

Statistics: Posted by Erwin Coumans — Tue Feb 26, 2019 12:52 am

Re: Remove Collision from an entire MultiBody

2019-02-19T11:34:25+00:00

Thanks a lot it works !!! and with the complexity of O(n²)

Here the final code for peoples who want it

Code:

# pop => Array of multibody personal class where is stored the unique ID and number of links and all the links matricesdef removeAllColisions(pop):    for elem in pop:        # Get the numbre of sub-object/links in the multibody        for i in range(-1, elem.nbobj):            p.setCollisionFilterGroupMask(elem.getId(), i, 0, 0)            p.setCollisionFilterPair(0, elem.getId(), -1, i, 1)

Statistics: Posted by Lewho — Tue Feb 19, 2019 11:34 am

Re: Remove Collision from an entire MultiBody

2019-02-19T00:18:53+00:00

PyBullet. setCollisionFilterGroupMask should be fixed in latest repository. Thanks for the report.

Note that link index -1 refers to the base, and link index >=0 refers to child links.
https://github.com/bulletphysics/bullet3/pull/2116

Statistics: Posted by Erwin Coumans — Tue Feb 19, 2019 12:18 am

Re: Remove Collision from an entire MultiBody

2019-02-12T14:10:44+00:00

No one respond .. nice. The issue is in fact still open on github (https://github.com/bulletphysics/bullet3/issues/2020) and erwin coumans ignore the BUG still 1 month after. The only way i found is complexity O(n^4) which it's very very bad conpare to the real who is O(n^2)

Solution for intrested person who need to have a proof of concept :

Code:

for i in range(-1, nbobj):        for j in range(-1, nbobj):            for elem1 in range(0, nbPop):                for elem2 in range(elem1+1, nbPop):                      p.setCollisionFilterPair(pop[elem1].getId(), pop[elem2].getId(), i, j, 0)        print((i+2)/(nbobj+1))

We need to remove the collision pair by pair so if you have 100 objects it's a 100*100 calculation. the fun doesn't end here.... if you have 10 piece in your multibody you need still to remove the collision pair by pair AGAIN. So it's actualy 100*100*10*10 calculation...

Statistics: Posted by Lewho — Tue Feb 12, 2019 2:10 pm

Remove Collision from an entire MultiBody

2019-02-07T22:18:51+00:00

Hi,

i have a certain number of random generated MultiBody with multiple links BUT i dont want them to collide beteen them and i also want them to keep colliding with my main plane floor.

I find a solution but it works only on the body of the multy body not on the links. Part of the problem is : i dont know what is the LinkIndex parameter in the setCollisionFilterGroupMask function.

My code at the moment :

Code:

p.createCollisionShape(p.GEOM_PLANE)basePlan = p.createMultiBody(0, 0)nbobj = 5body = p.createCollisionShape(p.GEOM_SPHERE, radius=1)body2 = p.createCollisionShape(p.GEOM_SPHERE, radius=0.5)aShape = s.Shape(body, pos1)aShape2 = s.Shape(body2, pos1)# intitialize multibody matrix for "nbobj" new linkaShape.createRandom(nbobj)aShape2.createRandom(nbobj)# do the createMultiBody and return the UniqueBodyidshape = aShape.createBody()shape2 = aShape2.createBody()# Do shape to not collidep.setCollisionFilterGroupMask(shape, -1, 0, 0)p.setCollisionFilterGroupMask(shape2, -1, 0, 0)# But enable the floor Collisionp.setCollisionFilterPair(basePlane, shape, -1, -1, 1)p.setCollisionFilterPair(basePlane, shape2, -1, -1, 1)

Statistics: Posted by Lewho — Thu Feb 07, 2019 10:18 pm