I'm standing on nothing

[Eileen Jazzhands]

Hello,

I ran into an odd phenomenon on my sim.  I was walking around my carnival and came across and area where I started to walk up, away from the ground.  At first I thought there was an invisible prim there but this picture is taken with "highlight invisible" turned on and there is clearly nothing.  I'm more curious than alarmed at this but I'd hate for guests to have to deal with this.  If anyone understands what's happening please let me know.  I'd like to fix the issue if possible.  No, I'm not flying and my hover is at 0.

Thank you,

Eileen O'Langhaim (Eileen Jazzhands)

[Nick0678]

Change the items in that spot to phantom. One of them is doing it, you will figure it out.

[Lindal Kidd]

There can be a few reasons for this.

You've already thought of one...an invisible prim.  Often, these are used to provide a collision surface for sculpty prims, which are usually made Phantom.  However, Highlight Transparent will reveal these.

Another is a "ghost prim".  This used to be a frequent problem.  You'd delete an object, and it would appear to be deleted, but physically it was still "there" and you could collide with it.  Removing these required a region re-start.  However, the underlying cause of this phenomenon was addressed years ago, and ghost prims are no longer a problem.  Or, if they are, it is extremely rare.

The most usual reason these days is an inappropriate physics type for an object.  If you look at the Options tab in the Build/Edit window, you can see that an object can be set to physics type "prim", "phantom", or "convex hull".   What these choices refer to is the collision envelope for an object.  The collision envelope is how SL determines that you have run into something.  You can think of it as a sort of invisible Saran Wrap around the object.

If the physics type is "prim", the collision envelope closely follows the outlines of the object.  This provides the most realistic interaction with it.  The downside is that it increases the land impact cost of the object.

If the physics type is "phantom", there is NO collision envelope.  You walk right through things without hindrance.  Most trees in SL are phantom, to allow you to fly through a forest without being hindered by the branches.

If the physics type is "convex hull", the object's land impact is generally much lower, because the collision envelope is simplified.  The invisible "Saran Wrap" bridges any gaps or holes in the object.  The downside of this is that the holes in hollowed out objects become impassable.

You can inspect your objects and see if any of them have convex hull as their physics type.  Pay special attention to things around the area, like fences.