How to correctly upload mesh

Building using prims, sculpties and meshes. Texture creation techniques.
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Ozwell Wayfarer
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How to correctly upload mesh

Post by Ozwell Wayfarer » Fri Jan 29, 2016 6:01 pm

There seem to be a number of threads relating to uploading mesh and various issues attached to it. So I thought I would offer some best practices for people.

This is a big issue with a number of facets. I will try to cover them all one at a time.

DISCLAMER - While I know more than a thing or two about this topic, I reserve the right to be wrong. We are all students and teachers. What is shared below is my workflow and what my customers receive when they shop at my store. These best practices are applicable to Kitely. I cannot speak for other grids who might have implemented their own system.

1. YOUR MODEL

This is aimed mostly at people finding things on the internet and trying to upload them. You must understand that a huge amount of objects you will find available for free are not suitable for virtual environments. They are designed for "rendering" or CAD (computer assisted design) and are "high poly". These objects take a long time for your CPU to calculate and are not intended for "real time" environments such as Opensim.

Polycount/Tricount is always context sensitive but a rough guide would look something like.

A rock - 20-300 tris
A basic chair - 20-100 tris
A cliff face - 500-2,000 tris
A house - 1,000-9,000 tris
A tree - 750- 8,000 tris
A castle or mansion - 6,000-20,000 tris.

Note the upper thresholds are rather generous. Most of these objects can be accomplished to a high standard while staying in the low end of the ranges I give. The golden rule is ALWAYS use as few tris as possible.

There really is nothing you should be uploading into virtual worlds over 20,000 tris. 99% of the time much, much less.

Your objects should ALWAYS be joined into the smallest number of pieces possible. A mesh can have 8 texturable faces (materials). Similarly your textures should be coalesced into as few texture maps as possible, or re-used where possible. Preferably both.

2.LOD

LOD (meaning Level of Detail) is a massive topic that I cant possible cover in its entirety. The concept you need to understand is that as you or your cam move away from an object, its LOD decreases, from highest to lowest. This is effected by the objects size. So a small object will require more LOD stages than a large one. It is also effected by your viewers "object and sculpts LOD" slider found in "preferences" under "graphics".

A LOD stage is basically a separate version of the model. You can make up to three of them. Usually, I only make one. So you have the original model and a "LOD" version, which is lower detail and in most cases lower poly count. You can use the auto generated ones provided by the uploader, but they tend to be a mess of triangles. You can play with the tri values of each, then click the adjacent numbers (under the "trinagles" and "vertices" headings) to view the model. But its best to upload your own.

So for instance, a large cliff would only need two LOD stages (original and LOD1), but an Apple would probably benefit from 2 LOD stages. I NEVER use the last LOD stage. Ever. Its pretty useless in all cases IMHO and in SL, it significantly increases Land Impact. So I avoid it. Nobody has ever complained in 4+ years.

3. GENERATE NORMALS

Normal mapping is a technique for faking lighting. You can make a low poly model look much smoother by checking the box and increasing the value to 90 or 180. If you notice your mesh has sharp, unpleasant lines under certain windlight conditions, re-upload it and try this.

4. PHYSICS

The dreaded physics. It is important to understand a big difference between SL and OS here. In SL if you choose no physics model, the item will upload as essentially "phantom" with no physics. This is NOT how it works here. In OS, the uploader will take your ORIGINAL model as the physics model. Which means you will have full physics by default, but unless your object is low poly to begin with, this will punish your computer in the long term. You might not notice with one item, but a region full of items uploaded in this way is a one way ticket to lag city.

The first question you should ask yourself with any item is do I need physics AT ALL? Unless your object will be directly walked on or bumped into, it does not need physics. So things like bowls, swords, picture frames, grass all require no physics. You can set no physics by setting your final LOD stage to 0 (as suggested earlier) and then selecting "lowest" in the physics menu. You will maybe get a few tris as the model, but thats ok because any object without physics should also be set to phantom.

Most objects can use a simple box. Which you can export from the blender open screen as a DAE. You then choose "upload from file..." in the physics menu.

Last I checked, the "analyse" button does not work in OS.

So now your all set. When you hit "calculate" it should take no more than 15-20 seconds for the "upload" button to appear. For small items, it should be almost instant. If it is not then either your original model is too high poly or your LOD stages and physics are not optimised.

So I hope that sets you on the right path and I welcome any questions or comments.
Last edited by Ozwell Wayfarer on Wed Feb 03, 2016 5:32 pm, edited 6 times in total.
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Re: How to correctly upload mesh

Post by Selby Evans » Fri Jan 29, 2016 7:53 pm

Ozwell Wayfarer wrote:There seem to be a number of threads relating to uploading mesh and various issues attached to it. So I thought I would offer some best practices for people.

This is a big issue with a number of facets. I will try to cover them all one at a time.
This is a valuable article. May I have your permission to reprint it as an invited article? If you prefer, you can send me a revised copy, but I see no need for revision.
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Re: How to correctly upload mesh

Post by Ozwell Wayfarer » Fri Jan 29, 2016 8:07 pm

Some questions From G+

Q: Does this apply to mesh clothes and attachments?

A: Yes. In the case of clothing, there is no need for a physics model. So I would advise setting the final LOD stage to 0 and then choosing "lowest" in the phys dropdown menu.

Q: "Your objects should ALWAYS be joined into the smallest number of pieces possible." - Why? Has this been tested? I realize that will keep the land impact down, but is it better for the server or viewer? Worse for the server or viewer?

A: While I have no concrete proof for this, I have tested it myself. I am assuming that, just like textures each piece of mesh needs to make a "draw call" to the server to make it rez and display. More draw calls equal more server load. I have no proof of that but I think my logic is sound and I do know that you will get lower PE/LI in SL if you join things up. So I assume the extra cost relates to server load.

Q: I was told NOT to tick the "generate normals box" since day 1 in SL. What gives?

A: Lol, thats a funny one, as I was told you MUST tick it from day 1. From my experimentation it really only has a lot of bearing on spherical objects. For instance, you might upload something and notice that it has lots of nasty jaggy lines under certain windlight and sun conditions (trees, rocks and terrain suffer from this). If you set the normals to 90, you will eliminate that nasty jaggy look and get a nice smooth shadow falloff. On blocky objects, this is rarely an issue.
Last edited by Ozwell Wayfarer on Mon Feb 01, 2016 2:03 pm, edited 4 times in total.
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Re: How to correctly upload mesh

Post by Ozwell Wayfarer » Fri Jan 29, 2016 8:08 pm

Selby Evans wrote:
Ozwell Wayfarer wrote:There seem to be a number of threads relating to uploading mesh and various issues attached to it. So I thought I would offer some best practices for people.

This is a big issue with a number of facets. I will try to cover them all one at a time.
This is a valuable article. May I have your permission to reprint it as an invited article? If you prefer, you can send me a revised copy, but I see no need for revision.
Of course Selby, be my guest! :) But it looks like there will be questions, so maybe wait until the dust settles on G+.
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Re: How to correctly upload mesh

Post by Selby Evans » Sat Jan 30, 2016 1:35 am

Thanks, OZ -- I am always scheduled well in advance, so the article will not come out for a couple of weeks. Meanwhile I will follow the conversation and pick up further info.
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Re: How to correctly upload mesh

Post by Shandon Loring » Sun Jan 31, 2016 3:57 am

I just posted a quick down & dirty tutorial on getting .obj files and converting them to .dae

Because it is important, and to help Ilan maintain his sanity, I have repeatedly said...
Pay attention to the permissions and licensing.

Some are free. Some you can buy and resell. Some say Personal and Educational Use Only. Some say otherwise.
If you're going to use these for anything other than personal use, you should consider including the exact licensing and permissions information with the item.

So I repeat... Pay attention to the permissions and licensing.

Anyway... check out the post, hopefully helpful to someone here...
viewtopic.php?f=25&t=3201
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Re: How to correctly upload mesh

Post by Brayla Sana » Mon Feb 01, 2016 4:57 am

You can use a plain physics cube to upload most decor items and especially wearables. Using a plain cube also cuts down on calculate times and upload errors. For trees, I use a transparent simplified physics mesh and leave the rest as physics_type none. Having good physics models makes the server happy :)

physics cube
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Re: How to correctly upload mesh

Post by Ozwell Wayfarer » Wed Feb 03, 2016 5:37 pm

Brayla Sana wrote:You can use a plain physics cube to upload most decor items and especially wearables. Using a plain cube also cuts down on calculate times and upload errors. For trees, I use a transparent simplified physics mesh and leave the rest as physics_type none. Having good physics models makes the server happy :)

physics cube
I agree, a cube is always favorable for things you generally just expect to bump into. Terrain and things that are walked upon are generally the only things that need more accurate physics models.

And though a cube is perfectly good, for wearables and things that require no physics at all I would encourage people to try setting the final LOD stage to zero and taking that as your physics model. Its usually just a single triangle. If you want to use the final LOD stage, you can always use the slot AFTER you select the physics from it. You can add a model and the physics you selected previously will remain unchanged.
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Re: How to correctly upload mesh

Post by Dot Matrix » Sun Nov 12, 2017 9:38 pm

There's a new article on the OpenSim wiki on how to upload mesh. Here it is:

http://opensimulator.org/wiki/How_To_Upload_Mesh
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Re: How to correctly upload mesh

Post by Mike Lorrey » Sat Aug 04, 2018 5:49 am

I have run into an issue where the meshermizer seems to grossly overcount the number of vertexes. I have a mesh that in blender counts at 22k verts, but the upload process rejects it claiming it is over 65k. I had to remove two parts of the mesh to make them separate pieces, so the main part is 11k verts to get it to upload. I would like to know why the upload process grossly overcounts vertexes.
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