Trying to use bounding box with weighted vertices, but...

Abelius

...well, it doesn't work as I expected.

For starters I receive this warning:

"UnityEngine.PolygonCollider2D does not support weighted or animated points. Collider points will not be animated and may have incorrect orientation. If you want to use it as a collider, please remove weights and animations from the bounding box in Spine editor."

Yeah well... of course I want to use it as a collider, lol.

My intention is to have three clickable areas in each character: head, torso and legs. The head is rigid by definition, so no problem. The torso... well, more or less the same. But the legs are obviously much more flexible, so a rigid "box" or polygon won't do when they're walking.

In other words, I need a weighted bounding box in Spine that translates their animated bending to a Unity polygon collider.

So, when I saw this feature I took for granted that it would be child's play for the runtimes, that are already deforming sprites like a boss, to simply change the point positions of a polygon collider in real time...

But it seems it's not, according to this old post:

Bounding box problem

From Pharan: "Avoid using weighted bounding boxes if you plan to use their shapes as Unity colliders.
Unity physics doesn't support colliders that warp. I don't know any game physics engines that do."

All this sounds... extremely and shockingly limiting.

I don't want to sound like a gratuitous whiny moron but... I can't really understand why it is so difficult to mirror the positions of those vertices with the positions of those points in a collider, if I can change them at runtime. I mean, I CAN change them by hand, but a script can't do it? :wonder:

In fact, it's not even scaling the whole thing correctly when I change the height of the character, even though "Follow Local Scale" is marked on the attached Bone Follower.

Anyways, I'd just like to confirm if this continues to be true or I'm doing something wrong. :rolleyes:

Nate

This limitation comes from the Unity side. Take a look at what it takes to modify a collider's vertices. IIRC you basically destroy the mesh and assign a new one. That can work, but it's slow and probably not something you can/want to do every frame.

Physics engines are complex beasts and I'm sure have their reasons why they can't allow vertices to be changed easily on the fly. Pharan was right, it is difficult or impossible in other physics engines too, such as Box2D.

Abelius

Thanks for the reply Nate.

Yeah, I've been reading and people talk about destructions and creations all the time. I didn't think the engine did that by just moving a point in edit move, tbh.

So I agree it would be bad practice, at the very least, trying to implement it for the kind of FPS we can have in skeletal animation.

That said, I have two follow-up questions...

What is the use case of a weighted bounding box, if it can't be replicated in Unity and needs to be always fixed.
I'm not really a proper coder, but is there an alternative way you'd do think I need? Apart from setting up multiple smaller colliders following the bones.

Thank you!

Nate

Bounding boxes are polygons attached to the skeleton. You can use them for many things other than physics colliders. You could do hit detection with them, handle collisions yourself using them, use them to draw polygons, or anything else that needs some vertices transformed by bones.

If your goal is to make something clickable, you don't need polygons anyway. Generally clicks don't need such accuracy. In fact you don't want such accuracy, instead you want to make it reasonable to click. You can just put rectangular colliders around the character parts, or detect the character was clicked using a point-circle hit detection.

Abelius

Nate ha scritto
Bounding boxes are polygons attached to the skeleton. You can use them for many things other than physics colliders. You could do hit detection with them, handle collisions yourself using them, use them to draw polygons, or anything else that needs some vertices transformed by bones.

Yes, I meant what's the purpose of being able to weigh the vertices of a bounding box in Spine, if later in Unity it doesn't "animate" them. I'm just curious why that feature is implemented in the editor.

Nate ha scritto
If your goal is to make something clickable, you don't need polygons anyway. Generally clicks don't need such accuracy. In fact you don't want such accuracy, instead you want to make it reasonable to click. You can just put rectangular colliders around the character parts, or detect the character was clicked using a point-circle hit detection.

Yup, I'll remove the weights and make multiple rectangles triggering the same event. My only concern is that they follow not only the translation and rotation but also the scale. I don't know why it didn't re-scale yesterday, but I guess I did something wrong.

Thanks!