UNDER THE HOOD
HITBOX SECRETS
Presented information applies strictly to animation behavior in Second Life, not to global SL mechanics.
‘Ello darling! Please park your pixel bottom in that red chair and allow me to explain a few things.
Let’s make something clear:
When it comes to animation, Second Life doesn’t give a rat’s ass about your avatar. On that plane, you do not exist. You are just an invisible form of life inside the cage of the avatar’s HitBox.
To fully understand what the heck I’m talking about, you need to see it with your own eyes. So go ahead and hit Developer → Render Metadata → Avatar Hitboxes.
Water? Shugar? Something stronger?
Now that you’ve exposed it, let’s break down some avatar animation behavior you’ve seen before but probably never made sense of.
Ever noticed some ‘Stand’ roaming AO animations making you go through nearby walls like you are a ghost? It is because you are. For the system, if your HitBox is not moving, you are not moving, so nothing in the world is actually pushing you away from nearby objects.
HitBox is keeping your avatar on a short leash, restricting it to roam more than 10m from it. So say goodbye to all your dreams of proper animation for very high diving platforms.
And speaking of animations that should, logically, stay in a final position - like jumping into water or climbing ladders - it is impossible to achieve without an additional script that moves the HitBox from point A to point B.
HitBox is simply not animatable.
It is controlled by your keyboard and movement inputs, and stays relative to the SL grid coordinates.
Any manipulation is achieved through scripts.
So when your “Couples HUD” is not aligning avatars the way you expect, stop whining and blaming the creator and look at the system itself.
Now, let’s see what is going on when you are working on furniture setup.
When you sit on an object, the HitBox with your avatar inside becomes a child prim of that object.
By “positioning avatar” you are, in fact, positioning the HitBox with the avatar inside. Keep in mind: your avatar and animation - they are invisible for the system.
As you are already sitting in that chair, go ahead and ADJUST position: what you will see is the HitBox moving, carrying the avatar with it.
Another important fact: the HitBox capsule size adapts to your avatar size. So when you align avatars via their center, you are not using the geometrical center of your avatar - you are using the HitBox center.
The entire mechanism is exactly like the off-sim principle - as long as the root prim is somewhere on the land, you can have a beautiful view of a tropical island beyond the sim border. But in this case - you are the island. 😉
To see it in action, go ahead and choose the ‘Ghost’ animation from the chair menu… and observe where you are and where your HitBox is. An image says a thousand words.
Next time when you adjust avatar position to the object, remember to turn on HitBox and observe how the adjuster beam behaves according to the HitBox. It might be interesting!
There is one little neat trick you could use HitBox for. As it is not a part of the avatar controlled by animation, it can be a perfect attachment point to test animations on your furniture before you invest in them.
Simply sit on a demo, attach your furniture to “Avatar Center”, and position the object according to the animation.
Then use the demo stand as usual. Well, you are a furniture creator - you know position tricks! 😊
‘Ello darling! Please park your pixel bottom in that red chair and allow me to explain a few things.
Let’s make something clear:
When it comes to animation, Second Life doesn’t give a rat’s ass about your avatar. On that plane, you do not exist. You are just an invisible form of life inside the cage of the avatar’s HitBox.
To fully understand what the heck I’m talking about, you need to see it with your own eyes. So go ahead and hit Developer → Render Metadata → Avatar Hitboxes.