A sculpty oddity/puzzle

I uploaded a simple cube with rounded edges, made with AC3D (I think it was the SL starting cube prim), with the intention of stretching them in SL. I made it as a cube so that the bounding box in SL streches with the visible prim, and there are no invisible, av-blocking, parts of it. Then I created 4 prims with the sculptie texture, and stretched and linked them into a simple sofa - 2 arms, a back and a seat. I put a sit target into the seat to avoid any "no room to sit there..." messages, and this is what I found.

When the 4 prims are linked with the seat as the root, an av standing up from the seat jumps a long way forward - as though jumping over a bounding box, but the bouding boxes are the size of the visible prims, and no bigger. When they are linked with either arm as the root, the av jumps a fair way to one side - maybe half the other distance. When they are linked with the back as root, the av goes into a perpetual non-moving walk until it is moved into the sofa. I tried every permutation of linking the 4 prims together, and there was no way to stand up normally. When 3 of the prims were linked, standing up was normal, but not with 4 of them.

Then I linked in a normal box prim, which improved the way the av stood up, even though it wasn't perfect. Then I removed the box prim, and the improved standing up remained, and remains in copies of the sofa. It's not a perfect stand up, but it's acceptable.

I even experimented by changing 3 of the sculpties - the 2 arms and the back - so there were a variety of sculpties in the sofa, but it didn't make any difference.

Does anyone have any idea what could be could be causing the odd standing up when the 4 sculptie prims are linked together?

It's not necessarily a sculptie problem. I have had that happen with regular prims, pose balls even, before. To the point where I flew off my sofa and through the back wall once landing outside the building. You can try a pose script in the prim, even a poseball, but just a standart sit-assist script may fix it. The client only really renders the prim as the sculpted shape as well, it actually is just a big sphere the size it would be if it wasn't sculpted. So that may have something to do with it as well. I find that using a poseball and setting my chairs to phantom helps to make for smoother use.

Interesting, but why would standing up be fine from one prim, when 2 are linked together, when 3 are linked together, but not when all 4 are linked together? And why would linking an ordinary prim into the set, even off to the side, change the standing up? It seems to me that sculpties aren't very good at all yet. Apart from that sort of problem, they change shape according to the distance you are seeing them from.

It's got nothing to do with sculpties, for the sole reason that the sim has no idea the shape of your sculpty as it doesn't parse texture data - so it treats it no differently then any other prim as far as calculating avatar collisions. If anything its probably easier to stand up off them since they have a rounded bounding shape.

I was tearing my hair out trying to get standing up to work on a video game machine I made that had a seat for the player - the seat was a simple cube box. No sculpties. You could sit on it just fine if it was unlinked, but linking it to the rest of the machine would cause the player to get stuck in it and twitch like a ferret on heroin when he tried to stand up. Setting the sit target slightly off to one side fixed it, so the av kinda gets squeezed out to the side.

I think it has more to do with the way the ancient havok system calculates physics against linksets - maybe the behavior here under Havok 4 will be better. Haven't really tested it...

I'll give it a whirl with Havoc 4. It'll be interesting to see if it behaves the same.

I've never had the problem with normal prims, and I make and sell seating furniture, but you're right about it not knowing the shape of a sculptie prim. At this point, it's still very puzzling because the bounding boxes are the shapes of the rectangular prims, as shown with the bboxes option in the Client menu, and with Stretch in Edit, so if they show correct bounding box shapes, then SL should be able to determine where to place an av when standing up off one - as it does when standing up when 3 or fewer of the prims are in the set. Standing up is perfect is those cases - there are no large invisible bounding boxes that are negotiated.

Those are the client bounding boxes - they may or may not represent the bounding box the sim will be considering when your avatar sets his butt on something

Yes but the point is, the stand up is perfectly normal when 3 or less of the sculpties are in the set. If the serverside bboxes were bigger, then it wouldn't be a normal stand up. It seems to me that some calculations are awry.

Anyway, I got around it by temporarily adding a 5th prim to the set - a non-sculptie. It's not a perfect stand up but it's acceptable. When the 5th prim is removed, the stand up doesn't change, and is still acceptable - and copies of the seat retain the acceptable stand up, so it's good. It's a flaw in the system, but I've got around it.