Maniphest T72716

Blender RigidBody Physics broken
Closed, Archived
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Assigned To
Philipp Oeser (lichtwerk)
Authored By
Tohny (Tohny)
Dec 27 2019, 12:30 AM
Tags
  • BF Blender
  • Physics
Subscribers
Philipp Oeser (lichtwerk)
Tohny (Tohny)

Description

System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 750 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.66
CPU: R5 2600
RAM: 16GB DDR4

Blender Version
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-12-04 11:32, hash: rBf1aa4d18d49d
Worked: (optional)

Short description of error
Objects fly away when I click play{F8245480}

Exact steps for others to reproduce the error
[Please describe the exact steps needed to reproduce the issue]
[Based on the default startup or an attached .blend file (as simple as possible)]

Related Objects

Event Timeline

Tohny (Tohny) created this task.Dec 27 2019, 12:30 AM
Tohny (Tohny) added a project: Physics.
Philipp Oeser (lichtwerk) closed this task as Archived.Dec 28 2019, 12:50 PM
Philipp Oeser (lichtwerk) claimed this task.
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).

I would not call this broken [2.79 behave the same way here]

Those spiky colliders are not always easy to set up, but here are a couple of things to consider:

  • have an eye on the collision margins [in your case the cup where those pencils drop into is 18cm in diameter but has a 4cm collision margin on each polygon -- which is much to high for a sensible sim]
  • mass can also play a role here [1kg pencils?]
  • pencils can get away with convex hull collision shapes [faster to simulate, avoids potential problems]

If I (quickly) adjust these a bit, I can get a sim that is reasonably stable:

Desk and Supplies_repro.blend1 MBDownload

to really dig into the "problem", here is where bullet has problems computing a normal for a tri (in your file):

btVector3& btVector3::normalize(): Assertion `!fuzzyZero()' failed.
1   raise                                                                                         0x7ffff1ae4e35 
2   abort                                                                                         0x7ffff1acf895 
3   __assert_fail_base.cold                                                                       0x7ffff1acf769 
4   __assert_fail                                                                                 0x7ffff1add566 
5   btVector3::normalize                                     btVector3.h                     300  0x4ad934e      
6   btPrimitiveTriangle::buildTriPlane                       btTriangleShapeEx.h             90   0x4afa0cc      
7   btGImpactCollisionAlgorithm::collide_sat_triangles       btGImpactCollisionAlgorithm.cpp 427  0x4af72c4      
8   btGImpactCollisionAlgorithm::gimpact_vs_gimpact          btGImpactCollisionAlgorithm.cpp 515  0x4af76de      
9   btGImpactCollisionAlgorithm::gimpact_vs_gimpact          btGImpactCollisionAlgorithm.cpp 489  0x4af7565      
10  btGImpactCollisionAlgorithm::gimpact_vs_gimpact          btGImpactCollisionAlgorithm.cpp 475  0x4af74af      
11  btGImpactCollisionAlgorithm::processCollision            btGImpactCollisionAlgorithm.cpp 887  0x4af89c3      
12  btCollisionDispatcher::defaultNearCallback               btCollisionDispatcher.cpp       279  0x4ad2ea7      
13  btCollisionPairCallback::processOverlap                  btCollisionDispatcher.cpp       230  0x4ad3877      
14  btHashedOverlappingPairCache::processAllOverlappingPairs btOverlappingPairCache.cpp      386  0x4ad0de6      
15  btCollisionDispatcher::dispatchAllCollisionPairs         btCollisionDispatcher.cpp       244  0x4ad2c97      
16  btCollisionWorld::performDiscreteCollisionDetection      btCollisionWorld.cpp            228  0x4ad50d7      
17  btDiscreteDynamicsWorld::internalSingleStepSimulation    btDiscreteDynamicsWorld.cpp     496  0x4b31e8d      
18  btDiscreteDynamicsWorld::stepSimulation                  btDiscreteDynamicsWorld.cpp     456  0x4b31d21      
19  RB_dworld_step_simulation                                rb_bullet_api.cpp               212  0x4702b23      
20  BKE_rigidbody_do_simulation                              rigidbody.c                     2037 0x3122bac

Anyways, this does not seem like a real bug in blender, will close...
(feel free though to comment again if you still think you've found a bug...)

Tohny (Tohny) added a comment.Jan 2 2020, 12:09 AM

Thank you for your support! I keep these tweaks in mind

Hans Goudey (HooglyBoogly) mentioned this in T76861: Rigidbody Mesh Collision Instability with Simple Torus.May 18 2020, 11:03 PM