CollideShapeCollector sometimes doesn't register hits?

[eliasdaler]

Hello. For some reason CollideShapeCollector sometimes doesn't report hits.

Am I doing something wrong? I'm doing something like this:

float interactionSphereRadius{0.75f};
glm::vec3 interactionSphereOffset{0.f, 1.f, 0.75f};
characterInteractionShape = new JPH::SphereShape(interactionSphereRadius);

// later ...
JPH::CollideShapeSettings settings;

// sync interaction sphere
// character is CharacterVirtual
// characterRotation is glm::quat
const auto sphereCenterPos = util::glmToJolt(
    character->GetPosition() + glm::vec3{0, 1, 0} * interactionSphereOffset.y +
    characterRotation * glm::vec3{0, 0, 1}  * interactionSphereOffset.z);

JPH::AllHitCollisionCollector<JPH::CollideShapeCollector> collector;
physicsSystem.GetNarrowPhaseQuery().CollideShape(
    characterInteractionShape,
    JPH::Vec3::sReplicate(1.0f),
    JPH::RMat44::sTranslation(sphereCenterPos),
    settings,
    JPH::RVec3(),
    collector);

// draw interaction sphere
debugRenderer.DrawSphere(sphereCenterPos, interactionSphereRadius, JPH::Color::sBlue);

bool had_hit = !collector.mHits.empty();
if (had_hit) {
    // Draw results
    for (const auto& hit : collector.mHits) {
        JPH::BodyLockRead lock(physicsSystem.GetBodyLockInterface(), hit.mBodyID2);
        if (lock.Succeeded()) {
            const JPH::Body& hit_body = lock.GetBody();

            // Draw bounding box
            JPH::Color color = hit_body.IsDynamic() ? JPH::Color::sRed : JPH::Color::sGreen;
            debugRenderer.DrawWireBox(
                hit_body.GetCenterOfMassTransform(),
                hit_body.GetShape()->GetLocalBounds(),
                color);
        }
    }
}

Overall, it works:

However, when the sphere penetrates the object deeper, the hit can stop registering:

Same can happen even for simple AABB:

[jrouwe]

Change:

JPH::CollideShapeSettings settings;

to

JPH::CollideShapeSettings settings;
settings.mBackFaceMode = EBackFaceMode::CollideWithBackFaces;

My guess is that your car is a MeshShape and that the sphere is back facing for all triangles.

[eliasdaler]

Thank you, this was indeed the solution!

And as far as I understand, if the shape is fully inside the mesh and doesn't intersect any of its triangles, the hit won't register too - right? And I would probably would have to use ConvexShape for that?

[jrouwe]

Correct