Collision Start weirdness

[Innula Zenovka]

I'm firing llVolumeDetect snowballs at people, and I need to know when they hit something so they can stop flying, turn invisible, trigger a particle effect and a sound, and then delete themselves.

What would cause, in the collision_start event, llOwnerSay("collided with "+(string)llDectectedKey(0)) to say "collided with 00000000-0000-0000-0000-000000000000)"  (i.e. null key)?

It's not entirely clear what, if anything, the snowball thinks it's hitting, since quite often it seems to be something in mid air about 3 or 4 metres from where they rezzed, that's not actually there. or at least it isn't immediatly obvious with wireframe, bounding boxes or physics shapes visible.   I've tried it on different regions, with similar results.   It's an intermittent but frequent issue.

 

 

Edited November 20, 2023 by Innula Zenovka

[Rolig Loon]

I've had projectiles collide with the weapon that fires them sometimes, but that should report the UUID of the weapon, not NULL_KEY.  And the way to beat that is to rez the projectile in front of the weapon, so it can't possibly touch it.

[Frionil Fang]

The only way I can reproduce something even somewhat similar:

Fire a bullet that is *not* volume detecting, but instead enables that in on_rez(). If it's moving slowly enough, I can then fire another bullet in a way that collides with the first: one of the bullets will report a null_key in a collision_end event, but haven't seen a single one in collision_start. It's a bit hard to determine without spending excessive effort, but I think the bullet that is not volume detect during that brief window after spawning reports a collision with a volume detect bullet, with all zero parameters (even the name and collision position are null). If the bullets are set to volume detect before rezzing (the property sticks with the object, after all, no need to call it during firing), they can't collide with each other in any manner.

As for the side note above, an attachment gun can't have its bullets collide with itself though: attachments don't have bounding boxes,. Any collision would be with the avatar itself, so the offset away from firing location is valid, anyway.

Edited November 20, 2023 by Frionil Fang

[Innula Zenovka]

Thanks, both.   The snowball "guns" are firing single snowballs, which rez 0,25 metres in front of the avatar.   The snowballs should normally travel comparatively slowly for about 12 or 13 metres before falling to the ground, unless they hit something first, at which point they lose their physics, stop, turn invisible and trigger some particles and sound effects before vanishing

When they exhibit this problematic behaviour they generally travel about 3.5 metres or so, and then stop in mid air, where they think they've hit something.   

I can't understand it.   It's not a big problem, and I've simply told the script to ignore collisions with NULL_KEY, but it's very puzzling.

[Wulfie Reanimator]

4 hours ago, Innula Zenovka said:

Thanks, both.   The snowball "guns" are firing single snowballs, which rez 0,25 metres in front of the avatar.   The snowballs should normally travel comparatively slowly for about 12 or 13 metres before falling to the ground, unless they hit something first, at which point they lose their physics, stop, turn invisible and trigger some particles and sound effects before vanishing

When they exhibit this problematic behaviour they generally travel about 3.5 metres or so, and then stop in mid air, where they think they've hit something.   

I can't understand it.   It's not a big problem, and I've simply told the script to ignore collisions with NULL_KEY, but it's very puzzling.

Would you pass a copy (with modifiable scripts) to me in-world? Seems like an interesting problem.

[Lucia Nightfire]

Does the navmesh view show ground at the height of impact?

There is a bug where bake issues cause invisible ground height "spikes" that only affect physical objects and not agents.

Collisions with these result in NULL_KEY with collision scripts.

It allegedly takes a region restart to fix.

Edited November 21, 2023 by Lucia Nightfire