Can't rezz on mesh

[Ina Fairport]

Edit : Creator offers help
 

Edited November 12, 2023 by Ina Fairport

[ChinRey]

23 hours ago, Ina Fairport said:

Edit : Creator offers help

That's nice to hear. I hope they figure it out and let us know if they need some advice.

This is a well known problem and it's caused by an undocumented quirk in SL's physic engine. It's fairly easy to fix once you know how to do it but it can't be done in-world, the mesh has to be reuploaded with a cirrected physics model.

[Quistess Alpha]

56 minutes ago, ChinRey said:

an undocumented quirk in SL's physic engine. It's fairly easy to fix once you know how to do it

Is it as easy to explain as it is to fix? I'm rather curious.

[ChinRey]

4 hours ago, Quistess Alpha said:

Is it as easy to explain as it is to fix? I'm rather curious.

There have been several explanations posted here over the years but finding older post on the SL forums is a nightmare. I managed to locate this though:

https://community.secondlife.com/forums/topic/409912-rezzing-things-on-mesh-floors/

It's not the best explanation but hopefully it will do as a start at least.

[Chic Aeon]

Had to smile at the "undocumented feature" comment.  Creators need to choose a PHYSICS model (if even a cube) but better yet in many cases like in houses MAKE a correct physics model.   It really would be better IMO if they uploader would just refuse to upload without a physics model.  

And the answer has been for over a decade "rez a prim and use that to rez on. A rug usually works fine and you can make your prim the size of a room and then make it invisible via the transparent choice in the build menu. 

Some of our "best" creators still are making houses that won't let you rez inside. A very sad state of affairs. 

[Ina Fairport]

5 hours ago, Chic Aeon said:

 

And the answer has been for over a decade "rez a prim and use that to rez on. A rug usually works fine and you can make your prim the size of a room and then make it invisible via the transparent choice in the build menu. 


 

That is exactly what I always did for many years.
In this house however I could not even rezz a box. I rezzed a box outside the house and dragged it into the house and on the floor, After resizing and make it transparent I can rezz whatever I want.
 

 

 

 

Edited November 13, 2023 by Ina Fairport

[Chic Aeon]

3 hours ago, Ina Fairport said:

That is exactly what I always did for many years.
In this house however I could not even rezz a box. I rezzed a box outside the house and dragged it into the house and on the floor, After resizing and make it transparent I can rezz whatever I want.

It is the same issue still of course. THEN you need to rez on the ground outside and drag it in to start with. it is a pain, agreed.    

[Ina Fairport]

Well, it has become a horror story, Yesterday after rezzing a transparent floor above the original floor the problem seemed solved.

Today I only could rezz basic prims. When I rezzed a radio, the radio just disappeared and came back in my inv after a relog and I can''t rezz mesh furniture.
The creator does not react anymore. It is a shame because he build very nice houses.

 

Edited November 13, 2023 by Ina Fairport

[ChinRey]

9 hours ago, Ina Fairport said:

Today I only could rezz basic prims. When I rezzed a radio, the radio just disappeared and came back in my inv after a relog and I can''t rezz mesh furniture.

Aww, sorry to hear that. All isn't lost though, you can always rez the furniture outside the house and drag in place. It's inconvenient but it works.

Edited November 14, 2023 by ChinRey

[Ina Fairport]

9 minutes ago, ChinRey said:

Aww, sorry to ehar that. All isn't lost though, you can always rez the furniture outside the house and drag in place. It's inconvenient but it works.

Yes, I will do that. It is a small house  on a small waterland parcel. My "sailhome" at Second Norway.

[Rya Nitely]

I thought they fixed it. I can upload using 'surface' and I can rez objects on the item with no issues.

I always forgot to choose 'solid' instead of 'surface' when I had the issue and needed to upload it again, but lately I haven't been experiencing the issue. I think it may have been within the past 12 months the issue disappeared for me.

I just tested again now and yes I can rez on surfaces without choosing 'solid' and using the default settings 'surface'. I also didn't analyse in this example.

In my experience something seems to have changed.

The images shows my upload settings, and the item after uploading it and throwing a fern on it.

And Chic , the uploader will choose a physics model for you if you don't choose one. I believe it's the low model. So it won't upload without some physics model. But you don't need a physics model for a phantom object like my fern in the image (except a triangle).

 

Furthermore, my imported model has a physics shape without choosing 'analyse'. It is set to prim and has hills and valleys like the physics shape shows.

Edited November 16, 2023 by Rya Nitely
more info

[Aquila Kytori]

8 hours ago, Rya Nitely said:

And Chic , the uploader will choose a physics model for you if you don't choose one. I believe it's the low model. So it won't upload without some physics model.

I don't think that is quite correct, so I did a test upload of a very simple one room model:

 

 and in the uploader I left the "Pick a Physics model" option blank. The uploader didn't add a physics model so that when rezzed, there was no Prim option in the Physics Shape Type drop-down.

 

9 hours ago, Rya Nitely said:

I just tested again now and yes I can rez on surfaces without choosing 'solid' and using the default settings 'surface'. I also didn't analyse in this example.

 

The images shows my upload settings, and the item after uploading it and throwing a fern on it.

 

Furthermore, my imported model has a physics shape without choosing 'analyse'. It is set to prim and has hills and valleys like the physics shape shows.

 

If you don't use the Analyze button then anything Step2: will have no effect on the Non Analyzed model. The Surface or Solid options only apply when we are going to Analyze the Physics model.

 

If we create a Triangle/Planes type physics model designed not to be analyzed in the Uploader:

 

and assign it in Step1: of the Physics tab of the uploader, we want the Uploader to do nothing to our physics model so that the collision surfaces will be exactly as we designed them to be in Blender, we there fore do not ask the uploader to analyze it.

 

If on the other hand we want the uploader to analyze our physics model, that's to say convert whatever we assign as a physics mesh into a collection of hulls, then we should create our physics mesh differently. Instead of quads and triangles we build our physics model using non overlapping hulls, usually box shapes:

 

In the Uploader with this new Physics model assigned we hit the Analyze button, the uploader has very little work to do because the physics model is already a collection of hulls so the result should be very similar to the original physics mesh we gave it. In this example 8 hulls in Blender and 8 hulls after the Analyzing  process.

 

Now we change the Method in Step 2: to Solid and again ask the uploader to Analyze our physics mesh, in this example something is not quite right. The physics now consists of a collection of 10 hulls which may increase our final LI cost.  When Solid method is used each hull will be 0.36 in Physics cost, 8 x 0.36 = 2.88  versus 10 x 0.36 = 3.6 . ( When Surface method is used  the uploader sometimes creates a lot more hulls than was expected but in these cases the 0.36 multiplier cost per hull is not used. Perhaps @ChinRey could explain why this is ? )

 

We can sometimes fix this by setting the Simplify method in Step 3: to Retain% and adjusting the Retain % value followed by hitting the Simplify button :

 

And BTW,  I didn't have any problems rezzing on the floor of the room which used the Analyzed physics version and had its Convert to Hulls method set to Surface

I guess because it was such a simple object.

 

[Chic Aeon]

Simplistically put the "best practices" rules have not really changed over time. If you have a simple décor item you can use a cube (or a hex which is now in FS menu --many thanks as I used to use my home made one and more steps there). 

For building or anything else that needs to have CORRECT PHYSICS == learn how to make a physics model.  I use cubes and analyze and Aquila likes planes. EITHER method will give you good physics when needed.  

Depending on how you make your mesh objects the uploader can and often does give you a reasonable and viable LOD mode; (IF YOU TEST IT).  But the uploader has never done a good job with physics.  You "can" oftentimes use the highest setting and the physics will work but this method is less than great and adds land impact to your build.   I have been known when feeling lazy to occasionally use the uploader for physics in Opensim where no one really cares about land impact (and the physics does work)  but I have NEVER used the uploader physics it in SL LOL.

 

ALWAYS CHECK THE INFO IN THE UPLOAD PANEL before uploadng.  

 

Thanks again for Aquila's great explanations that will hopefully keep helping folks learn.  

[ChinRey]

5 hours ago, Aquila Kytori said:

Perhaps @ChinRey could explain why this is ? )

No, I can't. There's no mention of it in either of the HAVOK manuals and it doesn't seem to make any sense. What I do know is that it's all about ray tracing. SL uses ray tracing to locate the surface an object is to be rezzed on and mesh surfaces you can't rez are also not detectable with the llCastRay() function (thanks to @animats for figuring that out). It's not as simple as those objects being "invisible" to ray tracing though. If it was, the item would just have been rezzed on the next object on the path. This is what happens if you point straight down at the surface but if you rez at an angle (which we usually do of course) it won't detect the next surface along the path either. It looks as if a faulty mesh deflects the ray tracing path somehow.

5 hours ago, Aquila Kytori said:

And BTW,  I didn't have any problems rezzing on the floor of the room which used the Analyzed physics version and had its Convert to Hulls method set to Surface

I guess because it was such a simple object.

Or it may be because of the way the hulls were generated. Try to make a hull manually from a simple cube. If the cube you use is solid with all six sides, it will work fine even with hull method set to surface. If it has one open side, it won't.

Edited November 16, 2023 by ChinRey

[Rya Nitely]

On 11/17/2023 at 3:07 AM, Aquila Kytori said:

And BTW,  I didn't have any problems rezzing on the floor of the room which used the Analyzed physics version and had its Convert to Hulls method set to Surface

I guess because it was such a simple object.

Sorry, I haven't checked responses until now. Thanks for your tests, Aquila,

Something has definitely changed.

It used to be the case that just a very simple object, like a flat plane, didn't allow you to rez items on it if you left it set to 'surface' in the uploader. I know this because I was often asked to re-upload objects I sold such as pond water etc. Then I had to use solid to get things to rez on it. Not anymore. I can use 'surface' and it works. It didn't in the past.