How to offset the point at which shapes are created.

[benjaminleezhiyuan]

Hello, the models in my program have a TransformComponent that has variable Translate as its origin. This is passed into Jolt to create the shape. However some of the origins for the models are not at the center of the model, some are on the surface for example. This causes the collision box created to be offset from the actual model.

Here you can see that the collider is offset in the Y axis.

And here is the floor rotated 180 to show that the size of the collider is correct just the origin is wrong.

I was able to calculate the center of the model by using min and max extents and with that was able to calculate the offset from Translate to modelCenter.

How can I change the origin of the collider in Jolt.

[jrouwe]

Wrap your BoxShape in a RotatedTranslatedShape to offset it.

[benjaminleezhiyuan]

void PhysicsSystem::addBody(TransformComponent& transform, RigidBodyComponent& rigidbody, MeshFilterComponent& mesh, UUID entityID) {
	ShapeRefC shape;
	ShapeSettings::ShapeResult shape_result;

	bodyIDMapUUID[rigidbody.bodyID] = entityID;

	calculateBoundingVolume(*mesh.Model, transform);

	switch (rigidbody.shape) {
	case RigidBodyType::Box: {
		// Create box shape settings
		glm::vec3 size = calculateBoxSize(transform.minExtent, transform.maxExtent) * 0.5f;
		BoxShapeSettings box_shape_settings(Vec3(size.x, size.y, size.z));
		box_shape_settings.SetEmbedded();
		shape_result = box_shape_settings.Create();
		shape = shape_result.Get();

		RotatedTranslatedShapeSettings offsetShape(RVec3(10.f, 10.f, 10.f), Quat::sIdentity(), shape);
		offsetShape.SetEmbedded();
		shape_result = offsetShape.Create();
		shape = shape_result.Get();
		break;
	}
	case RigidBodyType::Sphere: {
		// Create sphere shape settings
		float radius = calculateSphereRadius(transform.minExtent,transform.maxExtent); // Assuming size.x represents the radius for a sphere
		SphereShapeSettings sphere_shape_settings(radius);
		sphere_shape_settings.SetEmbedded();
		shape_result = sphere_shape_settings.Create();
		shape = shape_result.Get();
		break;
	}
	case RigidBodyType::Capsule: {
		// Create capsule shape settings
		float radius = rigidbody.radius;     // Assuming size.x represents the radius for a capsule
		float halfHeight = rigidbody.halfHeight; // Assuming size.y represents the half height for a capsule
		CapsuleShapeSettings capsule_shape_settings(radius, halfHeight);
		capsule_shape_settings.SetEmbedded();
		shape_result = capsule_shape_settings.Create();
		shape = shape_result.Get();
		break;
	}
	default:
		// Handle error for unsupported shape type
		return;
	}

	if (!shape) {
		// Handle error (e.g., failed to create shape)
		return;
	}

	// Create the settings for the body itself, including other properties like restitution and friction
	BodyCreationSettings body_settings(shape, RVec3(transform.Translate.x, transform.Translate.y, transform.Translate.z), Quat::sIdentity(), EMotionType::Static, Layers::NON_MOVING);
	body_settings.mFriction = rigidbody.friction;
	body_settings.mRestitution = rigidbody.bounciness;

	if (rigidbody.dynamicBody) {
		body_settings.mMotionType = EMotionType::Dynamic;
		body_settings.mObjectLayer = Layers::MOVING;
	}

	// Create the actual rigid body
	Body* body = sData.body_interface->CreateBody(body_settings); // Handle nullptr in a real scenario
	if (!body) {
		// Handle error (e.g., failed to create body)
		return;
	}

	// Add it to the world
	sData.body_interface->AddBody(body->GetID(), EActivation::Activate);

	// Store the BodyID in the RigidBodyComponent
	rigidbody.bodyID = body->GetID().GetIndexAndSequenceNumber();
}

I've tried to set the offset but it still looks the same as the previously shown image. Currently only concerned with Box only

[jrouwe]

I would say that should work. How are you drawing your boxes? Do you use DebugRenderer (or DebugRendererSimple)?

[benjaminleezhiyuan]

The boxes are drawn using some custom renderer.
But I've found a fix to the problem as there were some issues with the values passed into jolt.