Mystery offset collision box in raycasts.

[arkiruthis]

I recently switched from Bullet to Jolt in my game. I'm only using raycasts on collision shapes. Unfortunately, my raycasts are hitting a 'shadow' or mystery mirror collision box which is offset. I don't think it's the CenterOfMass issue that is mentioned in the documentation.

https://www.youtube.com/watch?v=r4bN1SKhmg0 (video example)

I use EnTT for entity component system and have a transform component that holds the newly created BodyID for when the body needs updating. I also set the Entity ID on the BodyID as user data so I can correlate the 2.

This is the setup for when I spawn an entity:

   // I have debugged these half extents and they are always good
   JPH::BoxShapeSettings box_settings(halfExtents, 0.f); // Have experimented with different values here as my boxes are somtimes under the 0.005f convex limit
   JPH::Shape::ShapeResult result = box_settings.Create();
   if (result.IsValid())
   {
       JPH::ShapeRefC collisionShape = result.Get();

       // Create body creation settings
       JPH::BodyCreationSettings body_settings(
           collisionShape,
           newPosition, // A JPH::Vec3 where the entity will be spawned in WorldSpace
           JPH::Quat::sIdentity(),
           mesh.isStatic ? JPH::EMotionType::Static : JPH::EMotionType::Kinematic,
           mesh.isStatic ? Layers::NON_MOVING : Layers::MOVING);

       // Use EnTT entity index to connect with BodyID
       body_settings.mUserData = static_cast<uint64_t>(static_cast<uint32_t>(e.ID()));

       e.MutableTransform().bodyID             = m_physics->CreateBody(body_settings);
   }

In my PhysicsManager instance, this is the CreateBody

BodyID PhysicsManager::CreateBody(const BodyCreationSettings &inSettings)
{
    BodyInterface &bodyInterface = m_pimpl->physicsSystem->GetBodyInterface();
    BodyID newID                 = bodyInterface.CreateAndAddBody(inSettings, EActivation::Activate);
    return newID;
}

And every physics cycle:

        {
            auto transformsView           = m_registry.view<nda::TransformComponent>();
            auto joltPhysics              = m_physics->System();
            BodyInterface &body_interface = joltPhysics->GetBodyInterface();
            std::for_each(
                transformsView.begin(),
                transformsView.end(),
                [this, &body_interface, &transformsView](auto e) {
                    const auto &transform = transformsView.get<nda::TransformComponent>(e);
                    const glm::vec3 &pos  = transform.Position();
                    const glm::quat &q    = transform.Orientation();

                    body_interface.SetPositionAndRotation(
                        transform.bodyID,
                        Vec3(pos.x, pos.y, pos.z),
                        Quat(q.x, q.y, q.z, q.w),
                        EActivation::DontActivate);
                });
        }

And lastly my RayCast function

std::pair<entt::entity, JPH::BodyID> PhysicsManager::RayCastClosest(const glm::vec3 &from, const glm::vec3 &to)
{
    // Perform a raycast
    // JPH::RayCast ray;
    JPH::RRayCast ray(nda::ToJolt(from), nda::ToJolt(to));
    JPH::RayCastResult rayCastResult;
    if (m_pimpl->physicsSystem->GetNarrowPhaseQuery().CastRay(ray, rayCastResult))
    {
        const auto bodyID = rayCastResult.mBodyID;
        // Now get the body itself in order to retrieve the user data
        const auto userData = m_pimpl->physicsSystem->GetBodyInterface().GetUserData(bodyID);

        if (userData)
        {
            const auto id = static_cast<entt::entity>(static_cast<uint32_t>(userData));
            return { id, bodyID };
        }
    }

    return { entt::null, JPH::BodyID() };
}

I've hit a bit of a brick wall here and despite stepping in through the debugger, verifying that the raycast TO/FROM is correct, I just can't seem to figure out why this mystery collision is happening. Grateful for any help at this point.

[jrouwe]

Try changing:

JPH::RRayCast ray(nda::ToJolt(from), nda::ToJolt(to));

to

JPH::RRayCast ray(nda::ToJolt(from), nda::ToJolt(to) - nda::ToJolt(from));

[arkiruthis]

Where is that Picard facepalm meme... how did I not see that??

You sir, are a goddamn legend. Thank you! 🙌