overlap testing in PxGjkQuery has a large gemetry error

[SHiziw]

Situation

When doing scene query, I have a box and the overlap testing zone is a custom cone.
The box is 4mm X 6mm X 10mm and the cone has 2mm radius and 11.8mm height.
Cone is from snippets: CustomCone : CustomConvex
The fuction: PxGjkQuery::overlap((*cone), geomSupport, m_globalPose, geometryGlobalTm) returns true even the box is 2mm away from the cone zone, that I think the geometry error is too large.

What I tried

• I tried to change PxTorlerancesScale() between 0.001 and 0.000 0001, the geometry error still exists.
• I tried api PxGjkQuery::proximityInfo(), adjusted toleranceLength, the geometry error still exists.
• I checked the margin settings and I left them as 0.

[vreutskyy]

Hello. It would be great if you could make a compilable code snippet reproducing this issue. Thanks

[SHiziw]

Hi, here's the snippet based on SnippetCustomConvex:

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//
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// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.  

// ****************************************************************************
// This snippet shows how to use GJK queries to create custom convex geometry.
// ****************************************************************************

#include <ctype.h>
#include <vector>
#include "PxPhysicsAPI.h"
#include "geometry/PxGjkQuery.h"
#include "CustomConvex.h"
#include "extensions/PxCustomGeometryExt.h"

// temporary disable this snippet, cannot work without rendering we cannot include GL directly
#ifdef RENDER_SNIPPET

#include "../snippetcommon/SnippetPrint.h"
#include "../snippetcommon/SnippetPVD.h"
#include "../snippetutils/SnippetUtils.h"
#include "../snippetrender/SnippetRender.h"

using namespace physx;

static PxDefaultAllocator gAllocator;
static PxDefaultErrorCallback gErrorCallback;
static PxFoundation* gFoundation = NULL;
static PxPhysics* gPhysics = NULL;
static PxDefaultCpuDispatcher* gDispatcher = NULL;
static PxScene* gScene = NULL;
static PxMaterial* gMaterial = NULL;
static PxPvd* gPvd = NULL;
//static std::vector<CustomConvex*> gConvexes;
static std::vector<PxCustomGeometryExt::BaseConvexCallbacks*> gConvexes;
static std::vector<PxRigidActor*> gActors;
struct RenderMesh;
static std::vector<RenderMesh*> gMeshes;

const PxReal coneHeight = 11.5911f / 1000.f;
const PxReal coneRadius = 3.1058f / 1000.f;
const PxTransform conePose = PxTransform(PxVec3(0.0f - 11.5911f / 2.f, 338.0f, 300.0f) / 1000.f/*, PxQuat(angle, PxVec3(0, 0, 1))*/);

PxVec3 BoxOrigin(0.f / 1000.f, 336.72f / 1000.f, 307.0f / 1000.f);
PxVec3 BoxHalfExtents(3.0f / 1000.f, 3.0f / 1000.f, 5.0f / 1000.f);

RenderMesh* createRenderCylinder(float radius, float height, float margin);
RenderMesh* createRenderCone(float height, float radius, float margin);
void destroyRenderMesh(RenderMesh* mesh);
void renderMesh(const RenderMesh& mesh, const PxTransform& pose, bool sleeping);
void renderRaycast(const PxVec3& origin, const PxVec3& unitDir, float maxDist, const PxRaycastHit* hit);
void renderSweepBox(const PxVec3& origin, const PxVec3& unitDir, float maxDist, const PxVec3& halfExtents, const PxSweepHit* hit);
void renderOverlapBox(const PxVec3& origin, const PxVec3& halfExtents, bool hit);

static PxRigidDynamic* createDynamic(const PxTransform& t, const PxGeometry& geometry, const PxVec3& velocity = PxVec3(0), PxReal density = 1.0f)
{
	PxRigidDynamic* dynamic = PxCreateDynamic(*gPhysics, t, geometry, *gMaterial, density);
	dynamic->setLinearVelocity(velocity);
	gScene->addActor(*dynamic);
	return dynamic;
}


static void createConeActor(float height, float radius, float margin, const PxTransform& pose)
{
	//CustomCone* cone = new CustomCone(height, radius, margin);
	PxCustomGeometryExt::ConeCallbacks* cone = new PxCustomGeometryExt::ConeCallbacks(height, radius, 0, margin);
	gConvexes.push_back(cone);

	PxRigidDynamic* actor = gPhysics->createRigidDynamic(pose);
	actor->setActorFlag(PxActorFlag::eVISUALIZATION, true);

	PxShape* shape = PxRigidActorExt::createExclusiveShape(*actor, PxCustomGeometry(*cone), *gMaterial);
	shape->setFlag(PxShapeFlag::eVISUALIZATION, true);
	PxRigidBodyExt::updateMassAndInertia(*actor, 100);
	gScene->addActor(*actor);
	gActors.push_back(actor);

	RenderMesh* mesh = createRenderCone(height, radius, margin);
	gMeshes.push_back(mesh);
}

void initPhysics(bool /*interactive*/)
{
	gFoundation = PxCreateFoundation(PX_PHYSICS_VERSION, gAllocator, gErrorCallback);

	gPvd = PxCreatePvd(*gFoundation);
	PxPvdTransport* transport = PxDefaultPvdSocketTransportCreate(PVD_HOST, 5425, 10);
	gPvd->connect(*transport, PxPvdInstrumentationFlag::eALL);

	PxTolerancesScale phyTolerance;
	phyTolerance.length = 1e-3f / 500.0f;
	phyTolerance.speed = 9.8e-3f / 500.0f;
	gPhysics = PxCreatePhysics(PX_PHYSICS_VERSION, *gFoundation, phyTolerance, true, gPvd);

	PxSceneDesc sceneDesc(gPhysics->getTolerancesScale());
	sceneDesc.gravity = PxVec3(0.0f, 0.0f, 0.0f);
	gDispatcher = PxDefaultCpuDispatcherCreate(2);
	sceneDesc.cpuDispatcher = gDispatcher;
	sceneDesc.filterShader = PxDefaultSimulationFilterShader;

	gScene = gPhysics->createScene(sceneDesc);
	gScene->setVisualizationParameter(PxVisualizationParameter::eCOLLISION_SHAPES, 1.0f);
	gScene->setVisualizationParameter(PxVisualizationParameter::eSCALE, 1.0f);

	PxPvdSceneClient* pvdClient = gScene->getScenePvdClient();
	if (pvdClient)
	{
		pvdClient->setScenePvdFlag(PxPvdSceneFlag::eTRANSMIT_CONSTRAINTS, true);
		pvdClient->setScenePvdFlag(PxPvdSceneFlag::eTRANSMIT_CONTACTS, true);
		pvdClient->setScenePvdFlag(PxPvdSceneFlag::eTRANSMIT_SCENEQUERIES, true);
	}

	gMaterial = gPhysics->createMaterial(0.5f, 0.5f, 0.6f);

	createConeActor(coneHeight, coneRadius, 0, conePose); ////////////////////// LOOK HERE //////////////////////////////////////
}

void debugRender()
{
	for (int i = 0; i < int(gConvexes.size()); ++i)
	{
		PxRigidActor* actor = gActors[i];
		RenderMesh* mesh = gMeshes[i];
		renderMesh(*mesh, actor->getGlobalPose(), !actor->is<PxRigidDynamic>() || actor->is<PxRigidDynamic>()->isSleeping());
	}

	PxOverlapBuffer buffer;
	////////////////////// LOOK HERE //////////////////////////////////////
	gScene->overlap(PxBoxGeometry(BoxHalfExtents), PxTransform(BoxOrigin), buffer, PxQueryFilterData(PxQueryFlag::eANY_HIT | PxQueryFlag::eDYNAMIC));
	renderOverlapBox(BoxOrigin, BoxHalfExtents, buffer.hasAnyHits());
	if (buffer.hasAnyHits())
	    printf("yes\n");
	else
	    printf("no\n");

}

void stepPhysics(bool /*interactive*/)
{
	gScene->simulate(1.0f / 60.0f);
	gScene->fetchResults(true);
}

void cleanupPhysics(bool /*interactive*/)
{
	while (!gConvexes.empty())
	{
		delete gConvexes.back();
		gConvexes.pop_back();
	}

	while (!gMeshes.empty())
	{
		destroyRenderMesh(gMeshes.back());
		gMeshes.pop_back();
	}

	while (!gActors.empty())
	{
		PX_RELEASE(gActors.back());
		gActors.pop_back();
	}

	PX_RELEASE(gScene);
	PX_RELEASE(gDispatcher);
	PX_RELEASE(gPhysics);
	if (gPvd)
	{
		PxPvdTransport* transport = gPvd->getTransport();
		gPvd->release();	gPvd = NULL;
		PX_RELEASE(transport);
	}
	PX_RELEASE(gFoundation);

	printf("SnippetCustomConvex done.\n");
}

void keyPress(unsigned char key, const PxTransform& camera)
{
	switch (toupper(key))
	{
	case ' ':	createDynamic(camera, PxSphereGeometry(.1f), camera.rotate(PxVec3(0, 0, -1)) * 100, 3.0f);	break;
	}
}

int snippetMain(int, const char* const*)
{
#ifdef RENDER_SNIPPET
	extern void renderLoop();
	renderLoop();
#else
	static const PxU32 frameCount = 100;
	initPhysics(false);
	for (PxU32 i = 0; i < frameCount; i++)
		stepPhysics(false);
	cleanupPhysics(false);
#endif

	return 0;
}

#else
int snippetMain(int, const char* const*)
{
	return 0;
}

#endif

Two objects are small, but I think they are not intersecting.

[vreutskyy]

Hi. Could you try modifying PhisX's code at this line
https://github.com/NVIDIA-Omniverse/PhysX/blob/e8c8deb2d548dc635db4f61083ea0e745c0102a0/physx/source/geomutils/src/GuGjkQuery.cpp#L245C2-L245C2

from
return status == GJK_CLOSE || status == GJK_CONTACT;
to
return status == GJK_CONTACT;

just to check if it helps.

GJK_CLOSE means that the shapes are almost touching. But in your case 'almost' seems bigger than the shapes themselves :)

[SHiziw]

Thank you for your reply and suggestion. I tried to modify the code, but now overlap does not trigger even if the two objects have intersected.
I moved the box shape to global pose: PxVec3 BoxOrigin(-8.f / 1000.f, 336.72f / 1000.f, 301.0f / 1000.f);

[vreutskyy]

I see, thanks. Can we try one more fix?
This line:

PhysX/physx/source/geomutils/src/gjk/GuGJKSimplex.h

Line 311 in e8c8deb

if(FAllGrtrOrEq(eps, area))

from
if(FAllGrtrOrEq(eps, area))

to
if(FAllGrtrOrEq(FMul(eps, eps), area))

Thanks

[SHiziw]

Thank you, it works.