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Marianne Little

Linking with mesh objects set to "None".

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I know that mesh that's set to "None" must be linked to a Prim.

But will larger linksets break if I keep on adding to them?

I have uploaded the walls and floors in 1 upload with custom physics, and set it to Prim. It is not 1 mesh object, but 4 that was uploaded together, and set to prim.

All the trim and windowframes was another upload, not physics, linked and set to "None", and linked to the prim walls/floors in one operation.

But after this, I added windows and other parts that's bought and "Convex hull" set by default. I added them, and the stairs I bought from OPQ. It seems that the adding broke something. I can not walk up the stairs. It worked in the test grid, I could go up and down the opening. But I did not link so many parts as I did in the main grid. Only the walls, floors and the trim.

 Should I waited so the root prim was the last one added? Is adding more and more to the linkset ruining it? I made sure the root was still a prim, not one of the new linked objects.

Can I have more than 1 object that is a prim? Should I export the floors and walls, join them in Blender so it's one object, and upload it again? I did not join first, bc I could need a small final adjustment.

Is it possible to have both None and Convex hull in a linkset with a root Prim, or should I keep Convex Hull objects out of the linkset? Or link all parts, my mesh and the bought mesh, set it to None and then link this set to the Prim walls/floors, and not add more?

I will not reply for many hours, because I am going to bed. I hope to be wiser tomorrow.

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The root object of a link set must have a physical model. It can't be set to "Physics: None". All the other objects in the linkset can be set to "None" if desired.

Any object set to "Physics: None" is not solid in-world, and if your stairs are set to "Physics: None", you fall through them.

The root object of a link set does not have to be a prim. It can be a mesh. 100% mesh linksets work fine.

 

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3 hours ago, animats said:

The root object of a link set must have a physical model. It can't be set to "Physics: None". All the other objects in the linkset can be set to "None" if desired.

Any object set to "Physics: None" is not solid in-world, and if your stairs are set to "Physics: None", you fall through them.

The root object of a link set does not have to be a prim. It can be a mesh. 100% mesh linksets work fine.

 

Okay, thanks. It appears I have done all right, then. As far as I can understand this and previous threads.

When I talk about "Prims" in this thread, I mean a mesh object uploaded whith physics and set to prim. It is not a prim created in SL.

  • My root = mesh object uploaded with custom physics and set to Prim = Check.
  • My stairs and windows that I bought = Convex hull =  Check. Stairs are still solid when linked.
  • All the details that does not need to be physics as lists around the walls, trim around the stairwell, up in the gavel, outside and inside = None and linked to the root prim that is uploaded with physics = Check.

It is no problem walking around on the floors, rez on the floors, I am stopped by the walls. Physics work as intended. It is the stairs that stop me. I even unlinket the trim around the stairs top, and made sure it is phantom. I still can't walk up. I walk half the way up.

I set furniture next to the stairs to phantom, in case a big bounding box or a shadow blocked the stairs. Still no luck.

I will have to unlink every thing and try again. I may have missed one.

I did not get any reply on this: Can it be more than 1 object that is physics and prim in a linkset? Let us say the root prim is obviosly Prim and Physics. But child prim 2, 3 and 4  is also Prim and Physics. Then child prim 5 - 21 is set to None. Child prim 22 - last prim is  Convex Hull.

Is this the correct way of linking? Or should it be so that I link the root prim at last? Can I add more to a linkset, and then a bounding box appear?

Can an object set to "none" revert to Convex Hull by itself?

 

 

Edited by Marianne Little
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what happens when the stairs are unlinked from the rest of the build ?  Can you walk up the stairs ?

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50 minutes ago, Marianne Little said:

It is no problem walking around on the floors, rez on the floors, I am stopped by the walls. Physics work as intended. It is the stairs that stop me. I even unlinket the trim around the stairs top, and made sure it is phantom. I still can't walk up. I walk half the way up.

That sounds like the classic thin upper floor problem. Is the upper floor with the stairwell a separate mesh? and is it less than 0.5 m thick?

Any mesh (or twisted prim) that has unanalyzed physics and dimensions less than 0.5 m will automatically be set to convex hull even if they show up as prim in the edit window.

 

4 minutes ago, Mollymews said:

what happens when the stairs are unlinked from the rest of the build ?  Can you walk up the stairs ?

I can absolutely guarantee it's not the stairs. All OPQ stairs were originally made for my own houses so I've used them and tested them over and over again myself.

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There’s a handy feature in firestorm viewer (not sure if others have it) that lets you see the physics shape of selected objects. It’s a little eye symbol with a dash through it. From memory it sits next to the box for selecting convex hull/prim/none. When you click on it the eye shows without the dash and any selected prims show a blue shape that is the physics. It’s very handy for discovering which prim is blocking the way. 
 

And to your question - yes I’ve had prims change state, possibly through my own unintended working, though possibly by themselves.

Edited by Peony Sweetwater
Correcting autocorrect!

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Chin, yes agree. Sometimes when linking we can think  a blocking issue is with a object when it is isn't. In Marianne's case, Marianne's gets blocked when going up the stairs. Immediate thought, must be the stairs.  Unlink the stairs. Walk up the stairs, still blocked. Ergo, is not the stairs. Has to be something else

Edited by Mollymews
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33 minutes ago, Mollymews said:

In Marianne's case, Marianne's gets blocked when going up the stairs. Immediate thought, must be the stairs.

Yes but apart from the fact that I've already tested those stairs, if the physics had been broken in a way to stop you from walking up them (which is extremely unlikely in the first place), you wouldn't be able to walk them at all. You would be stopped at the bottom, not halfway up.

Edited by ChinRey
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2 hours ago, Peony Swee*****er said:

There’s a handy feature in firestorm viewer (not sure if others have it) that lets you see the physics shape of selected objects.

It's standard in all viewers although in other viewers you have to look in the Develop menu for it.

It's not totally reliable though and the bug I mentioned in my first post is one of the things that won't show up.

(Maestro LInden once told me that he never trusted the physics shape display and recommended we use the pathfinding/navmesh obstacle display options instead. Apparently he deluded himself into believeing that pathfinding actually was a useful function and that everybody in SL were happy to waste time keeping their land's navmesh up to date.)

Edited by ChinRey
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I think I found the problem. In the Physics, after I choose "From File" and the custom physic, I did not click "Analyze". As soon as I did it, the opening let me walk up.

I think this is causing me to hoover a bit over the first floor too. If "Analyze" is ticked off, my shoes hit the floor perfect. Well,as perfect as it can be in Second Life. The earlier upload in the Beta grid worked as it should.

Lots of work, but I learned something now.

I don't know what makes the physic better when I click "Analyze", but it does something good. It did for my floor. 😁

Edited by Marianne Little
added more info + grammar

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2 minutes ago, Marianne Little said:

I I think this is causing me to hoover a bit over the first floor too. If "Analyze" is ticked off, my shoes hit the floor perfect.

Yes. That's the pesky probem with stairwells in SL.

Analyzed physics isn't really suitable for walkable surfaces partly becuase it's not precise enough, partly because unless you do it exactly right you end up with surfaces you can't rez on.

Unanalyzed physics on the other hand, does give more precise tracking and always rez friendly srufaces but SL flatly refuses to handle it for objects with the dimensions you typicall have for a floor.

 

12 minutes ago, Marianne Little said:

I don't know what makes the physic better when I click "Analyze", but it does something good. It did for my floor. 😁

I'm not sure how much I should go into details but the most fundamental difference is that analyzed phsyics is volume based, unanalyzed is surface based.

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19 minutes ago, ChinRey said:

Yes. That's the pesky probem with stairwells in SL.

Analyzed physics isn't really suitable for walkable surfaces partly becuase it's not precise enough, partly because unless you do it exactly right you end up with surfaces you can't rez on.

Unanalyzed physics on the other hand, does give more precise tracking and always rez friendly srufaces but SL flatly refuses to handle it for objects with the dimensions you typicall have for a floor.

 

I'm not sure how much I should go into details but the most fundamental difference is that analyzed phsyics is volume based, unanalyzed is surface based.

The idiot version is: Click analyze if you will walk through small openings?

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3 hours ago, ChinRey said:

Yes but apart from the fact that I've already tested those stairs, if the physics had been broken in a way to stop you from walking up them (which is extremely unlikely in the first place), you wouldn't be able to walk them at all. You would be stopped at the bottom, not halfway up.

Yep, I never have issuses with OPQ ❤️ and have used the stairs before. I thought the linking had done something wrong. SL sometimes do things I don't understand. It is just annoying.

 

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Stairs that work, floors I can rez on, very large room downstairs, 2 rooms upstairs. No one makes LH add-ons that I want, and the standard reply to that is "Well, make one yourself". That I did.

32 LI in total, 29 + 3 for the doors.

Edit: I fixed the siding texture repeat to the left so it matches.

 

coll add-on.jpg

Edited by Marianne Little
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1 hour ago, Marianne Little said:

The idiot version is: Click analyze if you will walk through small openings?

More or less yes but the only time I can think of when you want to use analyzed physics, is for single walls with a doorway. Like this:

image.png.b91b6779c119877620b97ad6b8d29c9d.png

Once you add depth to the mesh, for example by adding a second wall, unanalyzed is nearly always better:

image.png.82309cd47ad062037a7225033a52ed70.png

The big problem is when you have a flat floor with a stairwell. Essentially this is a single wall with opening rotated to lie horizontally:

image.png.0e3f349b232009e2e65ac0162de3a098.png

You can not use unanalyzed physics for this because then the opening will be closed. And you don't want to use analzyed physics because (among other things) the hovering height will be off and unpredictably so.

One very simple solution is to rotate the floor 45 degrees before you export from Blender and then back after you've uploaded:

image.png.269433643c21820288f9ef7590de4da7.png

That's not a common solution though and it'll cause you a lot of headache of the trigonometry kind if you ever want to resize the mesh.

A more common solution is to add a hidden triangle to increase the nominal thickness:

image.png.c0b0e85927a3a64d5bee6cdb244da9ae.png

Of course, make sure it actually is hidden inside a wall or something.

I prefer to see it as an opportunity rather than a problem whenever possible. An opportunity to add some nice roofbeams perhaps:

image.png.3bb2295d2cbb04a252fcec36546aea2f.png

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Different colors for different floors, like tiles, wood.

The opening for the stairs against us. The floor is 20 cm thick with the lower = white ceiling. It was built in SL and saved as Collada, then joined in Blender.

Maybe I did wrong in not removing all the faces. I let the ones around the stair opening be white. I'm not selling it, so I can live with the flaws myself.

 

second floor.png

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