btGjkEpaSolver2 error

[sandeep_slash]

I'm doing a simple collision check between a composite object and a BvhTriangleMesh in my app.

I don't know why, but I'm getting this error in btGjkEpaSolver2::Penetration(....)

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Run-Time Check Failure #2 - Stack around the variable 'gjk' was corrupted.

Run-Time Check Failure #2 - Stack around the variable 'epa' was corrupted.

[Nathanael]

You have to provide more information and/or code sample to reproduce the problem.

[sandeep_slash]

Alrite,
This is the stuff which I tried in one of the BulletDemos and it works fine....

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   btCollisionShape* pBoxShape;
   btCollisionShape* pCylinderShape;
   btTransform childTransform;

   m_pParentShape = new btCompoundShape;

   btTransform parentTransform;
   parentTransform.setIdentity();
   parentTransform.setOrigin(btVector3(0, 5, 0));

   //Body Part1
   pBoxShape = new btBoxShape(btVector3(1.73667014, 0.848335028, 1.68590808));
   childTransform.setIdentity();
   childTransform.setOrigin(btVector3(0, 0.710668027, -1.82743204));
   
   m_pParentShape->addChildShape(childTransform, pBoxShape);

   //Body Part2
   pBoxShape = new btBoxShape(btVector3(1.48286009, 1.10214508, 1.86357510));
   childTransform.setIdentity();
   childTransform.setOrigin(btVector3(0, 0.888335049, 0));
   m_pParentShape->addChildShape(childTransform, pBoxShape);

   //Body Part3
   pBoxShape = new btBoxShape(btVector3(1.60976505, 0.340715021, 1.22905004));
   childTransform.setIdentity();
   childTransform.setOrigin(btVector3(0, 0.634525001, 1.71321750));
   m_pParentShape->addChildShape(childTransform, pBoxShape);

   //Wheel1
   pCylinderShape = new btCylinderShape(btVector3(0.416858017, 0.213810027, 0.416858017));
   //childTransform.setIdentity();
   childTransform.getBasis().setRotation(btQuaternion(0, 0.707, 0.0, 1.0));
   childTransform.setOrigin(btVector3(0.989859045, 0.225648522, 1.57362199));
   m_pParentShape->addChildShape(childTransform, pCylinderShape);

   //Wheel2
   pCylinderShape = new btCylinderShape(btVector3(0.416858017, 0.213810027, 0.416858017));
   //childTransform.setIdentity();
   childTransform.getBasis().setRotation(btQuaternion(0, 0.707, 0.0, 1.0));
   childTransform.setOrigin(btVector3(-0.989859045, 0.225648522, 1.57362199));
   m_pParentShape->addChildShape(childTransform, pCylinderShape);

   //Wheel3
   pCylinderShape = new btCylinderShape(btVector3(0.416858017, 0.213810027, 0.416858017));
   //childTransform.setIdentity();
   childTransform.getBasis().setRotation(btQuaternion(0, 0.707, 0.0, 1.0));
   childTransform.setOrigin(btVector3(0.989859045, 0.225648522, -1.57362199));
   m_pParentShape->addChildShape(childTransform, pCylinderShape);

   //Wheel4
   pCylinderShape = new btCylinderShape(btVector3(0.416858017, 0.213810027, 0.416858017));
   //childTransform.setIdentity();
   childTransform.getBasis().setRotation(btQuaternion(0, 0.707, 0.0, 1.0));
   childTransform.setOrigin(btVector3(-0.989859045, 0.225648522, -1.57362199));
   m_pParentShape->addChildShape(childTransform, pCylinderShape);

   m_collisionShapes.push_back(m_pParentShape);

   m_pParentBody = DemoApplication::localCreateRigidBody(1.0f, parentTransform, m_pParentShape);

I've the same stuff in my game, running on the XBOX 360. I'm doing collision between this composite object and a static BvhTriangleMesh....

[Nathanael]

I can see two likely possibilities for your problem:
1- when GjkEpa2::Penetration is called , there's just not enough stack space free to allocation instances of epa on it, if so, you can try to allocate epa on the heap, here's a quick patch to test that:

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case	GJK::eStatus::Inside:
		{
		EPA&				epa(*(new EPA()));
		EPA::eStatus::_	epa_status=epa.Evaluate(gjk,-guess);
		if(epa_status!=EPA::eStatus::Failed)
			{
			btVector3	w0=btVector3(0,0,0);
			for(U i=0;i<epa.m_result.rank;++i)
				{
				w0+=shape.Support(epa.m_result.c[i]->d,0)*epa.m_result.p[i];
				}
			results.status			=	sResults::Penetrating;
			results.witnesses[0]	=	wtrs0*w0;
			results.witnesses[1]	=	wtrs0*(w0-epa.m_normal*epa.m_depth);
			results.normal			=	-epa.m_normal;
			results.distance		=	-epa.m_depth;
                        delete &epa;
			return(true);
			} else { delete &epa;results.status=sResults::EPA_Failed; }
		}

2- EPA has a bug, and address epa::m_sv_store and/or epa::m_fv_store beyond allocated limits.
Its unlikely but possible, if patch#1 doesn't work, that the next thing to look at.

Hope it help,
Nathanael.

[sandeep_slash]

Thanks for your reply Nathanael...

The problem is, it never comes inside the switch(gjk_status) statement. gjk_status is always "Valid"

One more thing I noticed is, in eStatus::_ Evaluate(const tShape& shapearg,const btVector3& guess)
shapearg.m_shapes looks invalid....

When I enable Win32ThreadSupport, it crashes in SpuCollisionShapes.cpp
int getShapeTypeSize(int shapeType) ===> //unsupported shapetype, please add here

I guess itz a common problem related to collision shape

[sandeep_slash]

in btGjkEpaSolver2::Penetration() func...

I tried stepping through gjk.Evaluate(...) function, and it actually stepped into (SpuGjkEpa2.cpp) eStatus::_ Evaluate()...

Thatz quite strange coz I've disabled MultiThreaded support.....

So I guess therez something wrong with my implementation.....

[sandeep_slash]

Nevermind... I fixed the issue..

thnx..