Repository: bulletphysics/bullet3

Issue:
Simple Cloth demo is crashing
Crashes with following error:
```
b3Printf: Selected demo: Simple Cloth
App_ExampleBrowser: /home/ambidextrvs/workspace/bullet3/examples/ExampleBrowser/OpenGLGuiHelper.cpp:1303: void OpenGLGuiHelper::computeSoftBodyVertices(btCollisionShape*, btAlignedObjectArray<GLInstanceVertex>&, btAlignedObjectArray<int>&): Assertion `collisionShape->getUserPointer()' failed.
b3Printf: Aborting and deleting SharedMemoryCommon object
App_ExampleBrowser: aborted example on signal 6
```

I'll try to submit a PR if I can figure it out. (pointers are appreciated)


Discussion:

Patch:
diff --git a/examples/ExtendedTutorials/SimpleCloth.cpp b/examples/ExtendedTutorials/SimpleCloth.cpp
index ec0dd337cf..0d62a2dc25 100644
--- a/examples/ExtendedTutorials/SimpleCloth.cpp
+++ b/examples/ExtendedTutorials/SimpleCloth.cpp
@@ -121,6 +121,7 @@ void SimpleClothExample::createSoftBody(const btScalar s,
 		fixed,true);
 	
 	cloth->getCollisionShape()->setMargin(0.001f);
+  cloth->getCollisionShape()->setUserPointer((void*)cloth);
 	cloth->generateBendingConstraints(2,cloth->appendMaterial());
 	cloth->setTotalMass(10); 
 	//cloth->m_cfg.citerations = 10;