TestRagdollCharacter crashes

[MeFisto94]

Hey Guys,
TestBoneRagdoll works like a charm, however TestRagdollCharacter leads to a native-bullet crash.

Linux 4.8.0 on Kubuntu 16.10

INFORMATION: Running on jMonkeyEngine 3.2-6295
 * Branch: master
 * Git Hash: 0bc6c64
 * Build Date: 2017-09-09

# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00007f165f296c00, pid=18841, tid=0x00007f165ec22700
#
# JRE version: Java(TM) SE Runtime Environment (8.0_131-b11) (build 1.8.0_131-b11)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.131-b11 mixed mode linux-amd64 compressed oops)
# Problematic frame:
# C  [libbulletjme.so+0xebc00]  btConvexShape::localGetSupportVertexWithoutMarginNonVirtual(btVector3 const&) const+0x2f0
#
# An error report file with more information is saved as:
# hs_err_pid18841.log

It's not HEAD but I did a quick git diff we shows there was nothing bullet related in between.

[stephengold]

I managed to reproduce the issue using native Bullet on Windows 7, so it's not a unix-specific issue. Here's the console log:

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x000007feddf11a5f, pid=7088, tid=0x0000000000001b5c
#
# JRE version: Java(TM) SE Runtime Environment (8.0_111-b14) (build 1.8.0_111-b14)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.111-b14 mixed mode windows-amd64 compressed oops)
# Problematic frame:
# C  [bulletjme.dll+0x21a5f]
#
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
#
# An error report file with more information is saved as:
# S:\Git\master\jmonkeyengine\jme3-examples\hs_err_pid7088.log

I verified that TestRagdollCharacter still works with jBullet.

[stephengold]

The issue may be related to bones such as "Sheath.R" for which no vertices have weights above the threshold (0.5). In this case, an empty array is passed to the HullCollisionShape constructor, resulting in an empty btConvexHullShape.

Perhaps Native Bullet's stepSimulation method can't cope with an empty btConvexHullShape.

[stephengold]

I've found a fix, so I'll assign this issue to myself.

[stephengold]

The crash no longer occurs in 'master' branch.