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NVIDIAGameWorks
Found bug in Gu::sweepSphereVSTri
I found a bug in function Gu::sweepSphereVSTri. In some case, it will miss collision.
Below code show the bug. The capsule should hit the triangle at point hitPos. But PxGeometryQuery::sweep do not find the hit.
void testSweepSphereTriangle()
{
const PxVec3 vertices[3] = { {7.33294010f, 79.6109009f, -26.9337997f}, {7.61456013f, 80.2574005f, -27.3008995f }, {7.33294010f, 80.2574005f, -26.9337997f} };
const PxU32 indices[3] = { 0, 1, 2 };
static float radius = 0.265350759f;
static float halfHeight = 0.340350509f;
const PxVec3 startPoint{ 7.74110079f,80.8543167f,-27.2595482f };
const PxQuat rot{ 0.f, 0.f,0.707106829f,0.707106829f };
const PxVec3 unitDir{ -0.929564953f, -0.0281119142f, 0.367584974f };
const PxReal distance{ 0.149537891f };
const PxVec3 hitPos{ 7.59219694f, 80.2574005f, -27.2717476f };
const PxReal hitDistance{ 0.0944127962f };
const PxVec3 p0 = hitPos - unitDir * hitDistance;
const physx::PxTransform pose0{ startPoint, rot};
const physx::PxTransform poseTri{ PxIdentity };
PxHitFlags hitFlags{ physx::PxHitFlag::eDEFAULT | physx::PxHitFlag::eMESH_BOTH_SIDES | physx::PxHitFlag::eASSUME_NO_INITIAL_OVERLAP };
PxTriangleMeshDesc meshDesc;
meshDesc.points.count = 3;
meshDesc.points.data = vertices;
meshDesc.points.stride = sizeof(PxVec3);
meshDesc.triangles.count = 1;
meshDesc.triangles.data = indices;
meshDesc.triangles.stride = 3 * sizeof(PxU32);
PxCookingParams params = gCooking->getParams();
PxTriangleMesh* triMesh = NULL;
triMesh = gCooking->createTriangleMesh(meshDesc, gPhysics->getPhysicsInsertionCallback());
PxTriangleMeshGeometry triGeom{ triMesh };
PxCapsuleGeometry capsuleGeom{ radius, halfHeight };
bool isInitOverlap = PxGeometryQuery::overlap(capsuleGeom, pose0, triGeom, poseTri);
printf("isInitOverlap = %d.\n", isInitOverlap);
physx::PxSweepHit hit;
PxU32 hitCount = PxGeometryQuery::sweep(unitDir, distance, capsuleGeom, pose0, triGeom, poseTri, hit, hitFlags);
printf("\nSweep capsule hitCount = %d.\n", hitCount);
if (hitCount > 0)
{
printf("hit position is (%f, %f, %f).\n", hit.position.x, hit.position.y, hit.position.z);
printf("hit normal is (%f, %f, %f).\n", hit.normal.x, hit.normal.y, hit.normal.z);
printf("hit distance is %f.\n", hit.distance);
}
PxTransform pose1{ startPoint + unitDir * distance, rot };
bool isResultOverlap = PxGeometryQuery::overlap(capsuleGeom, pose1, triGeom, poseTri);
printf("\nisResultOverlap = %d.\n", isResultOverlap);
PxReal p0ToCapsule = PxGeometryQuery::pointDistance(p0, capsuleGeom, pose0);
printf("\np0(%f, %f, %f) %s capsule\n", p0.x, p0.y, p0.z, (p0ToCapsule <= 0.f) ? "is in" : "is not in");
physx::PxRaycastHit rayHits[1];
hitCount = PxGeometryQuery::raycast(p0, unitDir, triGeom, poseTri, distance, hitFlags, 1, rayHits);
printf("raycast p0 hitCount = %d.\n", hitCount);
if (hitCount > 0)
{
printf("raycast hit position is (%f, %f, %f).\n", rayHits[0].position.x, rayHits[0].position.y, rayHits[0].position.z);
printf("raycast hit normal is (%f, %f, %f).\n", rayHits[0].normal.x, rayHits[0].normal.y, rayHits[0].normal.z);
printf("raycast hit distance is %f.\n", rayHits[0].distance);
}
triMesh->release();
}
I found the bug is in function Gu::sweepSphereVSTri. It says as below:
//
// Let's do some art!
//
// The triangle gets divided into the following areas (based on the barycentric coordinates (u,v)):
//
// \ A0 /
// \ /
// \ /
// \/ 0
// A02 * A01
// u / / \ \ v
// * / \ *
// / \ .
// 2 / \ 1
// ------*--------------*-------
// / \ .
// A2 / A12 \ A1
//
//
// Based on the area where the computed triangle plane intersection point lies in, a different sweep test will be applied.
//
// A) A01, A02, A12 : Test sphere against the corresponding edge
// B) A0, A1, A2 : Test sphere against the corresponding vertex
//
// Unfortunately, B) does not work for long, thin triangles. Hence there is some extra code which does a conservative check and
// switches to edge tests if necessary.
//
When test sphere against vertex, this function only test with sphere. This may miss contact. In this case, both edge should be tested.
Below patch can fix this problem.
.../geomutils/src/sweep/GuSweepSphereTriangle.cpp | 59 +++++++++++++---------
1 file changed, 35 insertions(+), 24 deletions(-)
diff --git a/physx/source/geomutils/src/sweep/GuSweepSphereTriangle.cpp b/physx/source/geomutils/src/sweep/GuSweepSphereTriangle.cpp
index a8e8d9b9..3470aaaa 100644
--- a/physx/source/geomutils/src/sweep/GuSweepSphereTriangle.cpp
+++ b/physx/source/geomutils/src/sweep/GuSweepSphereTriangle.cpp
@@ -86,7 +86,7 @@ static PX_FORCE_INLINE PxU32 rayTriSpecial(const PxVec3& orig, const PxVec3& dir
// Returns true if sphere can be tested against triangle vertex, false if edge test should be performed
//
// Uses a conservative approach to work for "sliver triangles" (long & thin) as well.
-static PX_FORCE_INLINE bool edgeOrVertexTest(const PxVec3& planeIntersectPoint, const PxVec3* PX_RESTRICT tri, PxU32 vertIntersectCandidate, PxU32 vert0, PxU32 vert1, PxU32& secondEdgeVert)
+static PX_FORCE_INLINE bool oneOrTwoEdgeTest(const PxVec3& planeIntersectPoint, const PxVec3* PX_RESTRICT tri, PxU32 vertIntersectCandidate, PxU32 vert0, PxU32 vert1, PxU32& secondEdgeVert)
{
{
const PxVec3 edge0 = tri[vertIntersectCandidate] - tri[vert0];
@@ -116,15 +116,26 @@ static PX_FORCE_INLINE bool edgeOrVertexTest(const PxVec3& planeIntersectPoint,
return true;
}
-static PX_FORCE_INLINE bool testRayVsSphereOrCapsule(PxReal& impactDistance, bool testSphere, const PxVec3& center, PxReal radius, const PxVec3& dir, const PxVec3* PX_RESTRICT verts, PxU32 e0, PxU32 e1)
+static PX_FORCE_INLINE bool testRayVsOneOrTwoCapsule(PxReal& impactDistance, bool testBothEdge, const PxVec3& center, PxReal radius, const PxVec3& dir, const PxVec3* PX_RESTRICT verts, PxU32 e0, PxU32 e1)
{
- if(testSphere)
+ if(testBothEdge)
{
PxReal t;
- if(intersectRaySphere(center, dir, PX_MAX_F32, verts[e0], radius, t))
+ if (intersectRayCapsule(center, dir, verts[e0], verts[(e0+1) % 3], radius, t))
{
- impactDistance = t;
- return true;
+ if (t >= 0.0f/* && t<MinDist*/)
+ {
+ impactDistance = t;
+ return true;
+ }
+ }
+ else if (intersectRayCapsule(center, dir, verts[e0], verts[(e0 + 2) % 3], radius, t))
+ {
+ if (t >= 0.0f/* && t<MinDist*/)
+ {
+ impactDistance = t;
+ return true;
+ }
}
}
else
@@ -214,7 +225,7 @@ bool Gu::sweepSphereVSTri(const PxVec3* PX_RESTRICT triVerts, const PxVec3& norm
// switches to edge tests if necessary.
//
- bool TestSphere;
+ bool TestBothEdge;
PxU32 e0,e1;
if(u<0.0f)
{
@@ -223,19 +234,19 @@ bool Gu::sweepSphereVSTri(const PxVec3* PX_RESTRICT triVerts, const PxVec3& norm
// 0 or 0-1 or 0-2
e0 = 0;
const PxVec3 intersectPoint = INTERSECT_POINT;
- TestSphere = edgeOrVertexTest(intersectPoint, triVerts, 0, 1, 2, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, triVerts, 0, 1, 2, e1);
}
else if(u+v>1.0f)
{
// 2 or 2-0 or 2-1
e0 = 2;
const PxVec3 intersectPoint = INTERSECT_POINT;
- TestSphere = edgeOrVertexTest(intersectPoint, triVerts, 2, 0, 1, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, triVerts, 2, 0, 1, e1);
}
else
{
// 0-2
- TestSphere = false;
+ TestBothEdge = false;
e0 = 0;
e1 = 2;
}
@@ -249,12 +260,12 @@ bool Gu::sweepSphereVSTri(const PxVec3* PX_RESTRICT triVerts, const PxVec3& norm
// 1 or 1-0 or 1-2
e0 = 1;
const PxVec3 intersectPoint = INTERSECT_POINT;
- TestSphere = edgeOrVertexTest(intersectPoint, triVerts, 1, 0, 2, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, triVerts, 1, 0, 2, e1);
}
else
{
// 0-1
- TestSphere = false;
+ TestBothEdge = false;
e0 = 0;
e1 = 1;
}
@@ -263,12 +274,12 @@ bool Gu::sweepSphereVSTri(const PxVec3* PX_RESTRICT triVerts, const PxVec3& norm
{
PX_ASSERT(u+v>=1.0f); // Else hit triangle
// 1-2
- TestSphere = false;
+ TestBothEdge = false;
e0 = 1;
e1 = 2;
}
}
- return testRayVsSphereOrCapsule(impactDistance, TestSphere, center, radius, dir, triVerts, e0, e1);
+ return testRayVsOneOrTwoCapsule(impactDistance, TestBothEdge, center, radius, dir, triVerts, e0, e1);
}
bool Gu::sweepSphereTriangles( PxU32 nbTris, const PxTriangle* PX_RESTRICT triangles, // Triangle data
@@ -451,7 +462,7 @@ bool Gu::sweepSphereVSQuad(const PxVec3* PX_RESTRICT quadVerts, const PxVec3& no
#define INTERSECT_POINT_Q (quadVerts[1]*u) + (quadVerts[2]*v) + (quadVerts[0] * (1.0f-u-v))
Ps::swap(u,v);
- bool TestSphere;
+ bool TestBothEdge;
PxU32 e0,e1;
if(u<0.0f)
{
@@ -460,19 +471,19 @@ bool Gu::sweepSphereVSQuad(const PxVec3* PX_RESTRICT quadVerts, const PxVec3& no
// 0 or 0-1 or 0-2
e0 = 0;
const PxVec3 intersectPoint = INTERSECT_POINT_Q;
- TestSphere = edgeOrVertexTest(intersectPoint, quadVerts, 0, 1, 2, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, quadVerts, 0, 1, 2, e1);
}
else if(v>1.0f)
{
// 1 or 1-0 or 1-3
e0 = 1;
const PxVec3 intersectPoint = INTERSECT_POINT_Q;
- TestSphere = edgeOrVertexTest(intersectPoint, quadVerts, 1, 0, 3, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, quadVerts, 1, 0, 3, e1);
}
else
{
// 0-1
- TestSphere = false;
+ TestBothEdge = false;
e0 = 0;
e1 = 1;
}
@@ -484,19 +495,19 @@ bool Gu::sweepSphereVSQuad(const PxVec3* PX_RESTRICT quadVerts, const PxVec3& no
// 2 or 2-0 or 2-3
e0 = 2;
const PxVec3 intersectPoint = INTERSECT_POINT_Q;
- TestSphere = edgeOrVertexTest(intersectPoint, quadVerts, 2, 0, 3, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, quadVerts, 2, 0, 3, e1);
}
else if(v>1.0f)
{
// 3 or 3-1 or 3-2
e0 = 3;
const PxVec3 intersectPoint = INTERSECT_POINT_Q;
- TestSphere = edgeOrVertexTest(intersectPoint, quadVerts, 3, 1, 2, e1);
+ TestBothEdge = oneOrTwoEdgeTest(intersectPoint, quadVerts, 3, 1, 2, e1);
}
else
{
// 2-3
- TestSphere = false;
+ TestBothEdge = false;
e0 = 2;
e1 = 3;
}
@@ -506,7 +517,7 @@ bool Gu::sweepSphereVSQuad(const PxVec3* PX_RESTRICT quadVerts, const PxVec3& no
if(v<0.0f)
{
// 0-2
- TestSphere = false;
+ TestBothEdge = false;
e0 = 0;
e1 = 2;
}
@@ -514,11 +525,11 @@ bool Gu::sweepSphereVSQuad(const PxVec3* PX_RESTRICT quadVerts, const PxVec3& no
{
PX_ASSERT(v>=1.0f); // Else hit quad
// 1-3
- TestSphere = false;
+ TestBothEdge = false;
e0 = 1;
e1 = 3;
}
}
- return testRayVsSphereOrCapsule(impactDistance, TestSphere, center, radius, dir, quadVerts, e0, e1);
+ return testRayVsOneOrTwoCapsule(impactDistance, TestBothEdge, center, radius, dir, quadVerts, e0, e1);
}
Thank you, yes, I think this is a duplicate of https://github.com/NVIDIAGameWorks/PhysX/issues/501
