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Physics solid after upload


Siyun Jeon
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Hi all,

I've recently tried to upload a simple mesh that was done with Mesh Generator (for convenience, I've done models with Blender in the past). But I'm currently stunned because of a weird problem. It's a simple row of windows on a mount with an opening for a door. I've made a separate physics model. When I upload the model and the physics, it shows perfectly well in the preview window. The physics is where it is supposed to be.  Then I upload it, set it to prim, but the physics all of a sudden has become solid. Why does it behave differently inworld than in the preview? What is firestorm's checker doing well what second life is doing bad?

I'm at a loss here ...

Best

Lilly

 

Screenshot1_001.jpg

physics preview.PNG

Screenshot1_004.jpg

uploaded model.JPG

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A mesh must be at least 0.5 meters in all dimensions when a triangle based physics shape is uploaded with it. The solution to that is, press the Analyze button to decompose the physics mesh into hulls.

To check if thats the problem, just stretch the mesh > 0.5 in the Y dimension, and see if the opening works correctly.

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3 hours ago, Lilly Kiyori said:

What is firestorm's checker doing well what second life is doing bad?

Beq Janus (Firestorm Viewer Developer) fixed the Firestorm viewer so that it displays the correct (Render metadata) > Physics Shapes for mesh walls like in your example.

See her blog from July 2017 that explains in detail what is happening :

https://beqsother.blogspot.com/2017/07/a-convexing-problem-fixing-doors.html

Quote from the end of the blog :

" In the meantime, I have updated Firestorm to correctly reflect the enforced laws of physics. This should greatly improve the use of the physics view as a debugging tool. "
 
Fixed in Firestorm but not in the LL viewer !
 
Edited by Aquila Kytori
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Sadly, the Jira that I raised https://jira.secondlife.com/browse/BUG-134006 was accepted but never actioned (either of the two options that I suggested); which has still left us with this silly situation where Firestorm and the Second Life server are agreed about what physics state and behaviour is, but the LL viewer is just wrong. 

Because of the number of times this question comes up, both for new builders and even those who have been around a while. I am adding a new "warning" on the FS mesh uploader. It will display a message if the default scale of uploaded object would lead it to be convex once inworld.

https://gyazo.com/2bc8cc06c1fad953d20692a07cc11c66

It doesn't fix anything but might save wasted linden dollars on uploads.

I have chased up that Jira today - perhaps we will get a better  server side behaviour gong forward which would be the best thing all round.)

 

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9 hours ago, arton Rotaru said:

That's true, but it's at least something! Funny how such a simple thing like a warning msg took just ~12 years untill someone got the idea. Kudos to Beq!

Time for some nostalgia ^_^

It's not nearly 12 years. If you read the comments from the Linden those two JIRAs were assigned to, it's obvious that LL still had no clue whatsoever about how mesh physics works as late as eight years ago and you obviously can't fix a problem if you don't know what it is.

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Thanks all. Analysing the physics worked fine and fits the purpose in this case. I will check adding in a small 3rd dimension on an additional surface that can be made transparent at a later time. That may be interesting for some places where there's space so it doesn't get in the way. But as you wrote above: if you don't know this you're just puzzled, and even doing a little bit of search I didn't find the proper postings. Perhaps because there are just too many postings out there that say "switch to prim", and at some point you just think "yea, I read that.", but don't really have better terms to narrow the search down until you already know what's wrong. Thanks for that warning message, that sure helps.

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  • 2 weeks later...

Well. It fixed it, but the resulting object hilarously has a LI of 17, considerably more than the prims. For a stupid row of windows, just because the server thinks "small" is one-dimensional. Adding a Linkset of two transparent prims to do the physics manually over the original object which is set phantom appears to be the solution with the smallest footprint, which - honestly - is a shame, just because the uploader has a one-dimensional virtual brain.

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1 hour ago, Lilly Kiyori said:

Well. It fixed it, but the resulting object hilarously has a LI of 17, considerably more than the prims. For a stupid row of windows, just because the server thinks "small" is one-dimensional. Adding a Linkset of two transparent prims to do the physics manually over the original object which is set phantom appears to be the solution with the smallest footprint, which - honestly - is a shame, just because the uploader has a one-dimensional virtual brain.

That sounds like something went wrong. The physics weight should be 0.72 for the 2 hulls needed for this.

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As arton has already said the Physics should be only

       2 thin boxes (exported as a single object)

      = 2 Hulls in the mesh uploader after hitting the Analyse button

      = Physics cost of 0.72 when rezzed and set to Physics shape Type : Prim (0.36 cost for each Hull)

 

771393616_1_windows.thumb.png.efc9fa30a9d450ad1d6a3abe9b2f2a64.png

 

In the mesh Uploader it should look similar to these screen_shots :

2_windows.thumb.png.eab692404c57b1e8d782d1683de806bb.png

 

In the physics menu after hitting the Analyze button it should show Hulls: 2 

and when Weights and Fees have been calculated it should show a Physics cost of   Analysed: 0.72  (this will be the Physics cost when it has been rezzed and set to Physics Shape Type: Prim)  :

3_windows.thumb.png.6e2589fbedfa28e020e4d12f58b441e2.png

 

Perhaps you could post a screen_shot of the uploaders Physics menu after calculating weights and fees ?

Edited by Aquila Kytori
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There really must have something gone wrong, as it did not make much sense to me either. Now that I do it again, it comes down to 0.720. Maybe I analysed the original model instead of the 2 prim physics after having played around with too many versions.

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