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Let's talk about LoD factor.


Tama Suki
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➤ Does the original mesh density affect the LoD factor?
If I import a plane with only one face (which then become two triangles in SL) and inside the viewer I enlarge it 64x64 will it glitching in any case in SL ?

➤ What is the default setting of the viewer regarding the LoD factor?
A newly born account that has no idea these things exist with what default setting will look at my meshes?

➤ Is there a perfect formula of the settings in the import menu when importing a mesh?

If anyone also wants to point me to useful tutorials I would appreciate it very much, thanks.

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LODs swap based on size of the object's bounding box, and distance from camera, multiplied by the LOD factor. Density, complexity, land impact, and anything else isn't important.

The default LOD factor varies between viewers. I think they're all between 1.0 and 2.0.

You can see the LOD swap distances in the Build Tools window, at least on Firestorm.

You can provide custom LOD models for each level during the import process, so you have complete control of what the object looks like.

Edited by Wulfie Reanimator
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One trap I fell into in my early days was thinking that arbitrarily breaking my model into smaller pieces in just two dimensions would reduce the LoD drop distance and indeed the LI.

It turns out it's actually based on the bounding box radius. Which is to say that in whichever dimension the bounding box is biggest will be what is considered for LOD

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25 minutes ago, Extrude Ragu said:

It turns out it's actually based on the bounding box radius. Which is to say that in whichever dimension the bounding box is biggest will be what is considered for LOD

Just now I've imported this mesh and then in SL I enlarged it to the maximum, 63x64x64. the topology is very simple and the density very light but the physics (taken from its own file) works perfectly and I can look at it from afar and the LoD factor is simply not a problem.
So the first thing to take into consideration I think is that SL just pretends that his life doesn't get complicated and he is your friend.

-

Edit

I've put the LoD factor at 1.25 and i think it should be the standard. The mesh holds up well.

Schermata 2021-12-22 alle 14.25.44.png

Edited by Tama Suki
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The default LoD factors are 1.25 on the SL viewer, and 2.0 on Firestorm.

Larger objects are more likely to disappear from view due to the user's draw distance, before seeing any significant LoD change.

10 hours ago, Tama Suki said:

If anyone also wants to point me to useful tutorials I would appreciate it very much, thanks.

I never found much on these specific topics, @Beq Janus has some detailed blog posts on LoD calculations.

The best tutorial you have is the beta grid, and lots and lots and lots of trial and error.

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7 hours ago, Wulfie Reanimator said:

LODs swap based on size of the object's bounding box, and distance from camera, multiplied by the LOD factor. Density, complexity, land impact, and anything else isn't important.

Also, all rigged mesh objects attached to an avatar swap LODs based on an unusual calculation of the avatar's bounding box rather than their own individual boxes. They all swap at the same time, and at much farther distances than if they were unrigged or placed directly in the world.

Edited by Quarrel Kukulcan
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8 hours ago, Wulfie Reanimator said:

LODs swap based on size of the object's bounding box, and distance from camera, multiplied by the LOD factor. Density, complexity, land impact, and anything else isn't important.

 

For the OP

 

BUT while the swap is based on size ---  complexity and density (not exactly sure how those differ so let's call it triangle - vertices count) can be quite important IF you are using the uploader pane to pick your LODs.    The more complex (draped fabric is a good example) the more likely the uploader will do a poor job. You can compensate for this by changing the numbers in the LOD boxes and TESTING. TESTING, TESTING. Better to make your mesh less complex to start out with. 

 

There is a point when an object gets really large that the lowest LODs are ignored.  I don't remember the rule on this but someone else will. 

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13 hours ago, Tama Suki said:

➤ Does the original mesh density affect the LoD factor?

Only if you use LoD models generated by the uploader but you don't want to do that of course. Even Linden Lab has finally admitted it isn't good enough and are trying to find a better solution. It took them ten years but better late than never I guess.

When you make proper LoD models manually, you decide how many and which tris and vertices to keep for each and the computer can't do anything to change it.

The swap distances between the models are, as others have already said, determined by the object's size and the LoD factor your viewer is set to. For those who aren't scared of maths, the formulas for meshes, sculpts and sphere, torus, ring and tube prims are:

  • high to mid: L1=√(x2 + y2 + z2)*0.6*Lf
  • mid to low: L2=L1*4
  • low to lowest: L3=L1*8

(Lf is the LoD factor you have set in your graphics preferences, x, y and z the dimensions along the three axises).

he other three prim types have slightly different formulas:

  • Cubes and prisms: L1=√(x2 + y2 + z2)*0.48*Lf
  • Cylinders: L1=√(x2 + y2)*0.6*Lf

The download weight which affects the land impact is calculated separately for each model according to their file sizes and then the four values are weighed towards each other based on how much area within a 181 m radius each covers when the LoD factor is set to 1. With a different LoD factor the download weight calculation is way off making it and thus the land impact basically just meaningless numbers.

As Quarrel mentioned, fitted mesh uses the bounding box size of the avatar to determine the LoD swap distances but the size the mesh was uploaded at to calculate the download and render weights. It's not umcommon for makers of fitted mesh to upload at the minimum (1x1x1 cm) size whilst the bounding box of a modern mesh avatar may well be much more than 10 m across. This of course means the calculation is way off and it's one of the reasons why the ARC (Avatar Render Complexity) figures we get are just random numbers with no meaning whatsoever.

 

Edited by ChinRey
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14 minutes ago, ChinRey said:

Only if you use LoD models generated by the uploader but you don't want to do that of course. Even Linden Lab has finally admitted it isn't good enough and are trying to find a better solution. It took them ten years but better late than never I guess.

When you make proper LoD models manually, you decide how many and which tris and vertices to keep for each and the computer can't do anything to change it.

The swap distances between the models are, as others have already said, determined by the object's size and the LoD factor your viewer is set to. For those who aren't scared of maths, the formulas for meshes, sculpts and sphere, torus, ring and tube prims are:

  • high to mid: L1=√(x2 + y2 + z2)*0.6*Lf
  • mid to low: L2=L1*4
  • low to lowest: L3=L1*8

(Lf is the LoD factor you have set in your graphics preferences, x, y and z the dimensions along the three axises).

he other three prim types have slightly different formulas:

  • Cubes and prisms: L1=√(x2 + y2 + z2)*0.48*Lf
  • Cylinders: L1=√(x2 + y2)*0.6*Lf

The download weight which affects the land impact is calculated separately for each model according to their file sizes and then the four values are weighed towards each other based on how much area within a 181 m radius each covers when the LoD factor is set to 1. With a different LoD factor the download weight calculation is way off making it and thus the land impact basically just meaningless numbers.

As Quarrel mentioned, fitted mesh uses the bounding box size of the avatar to determine the LoD swap distances but the size the mesh was uploaded at to calculate the download and render weights. It's not umcommon for makers of fitted mesh to upload at the minimum (1x1x1 cm) size whilst the bounding box of a modern mesh avatar may well be much more than 10 m across. This of course means the calculation is way off and it's one of the reasons why the ARC (Avatar Render Complexity) figures we get are just random numbers with no meaning whatsoever.

 

Epic!
I would love to follow you inworld, with your permission, and have some small talk there when you have time.

I need some tech help with my installation.

Edited by Tama Suki
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3 hours ago, Mr Amore said:

The default LoD factors are 1.25 on the SL viewer, and 2.0 on Firestorm.

Is 1.25 fixed or is that tied to a graphics preset?

In my own sim, due to the nature of being an anime sim people tend to have gaming computers, and my policy has always been to try to support Medium to Ultra Presets, I usually test my models at LOD 2, Draw Distance 64 as a 'worst case' scenario. (Mid in Firestorm being LOD 2, Draw distance 128)

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3 hours ago, Mr Amore said:

Larger objects are more likely to disappear from view due to the user's draw distance, before seeing any significant LoD change.

I take note. But I have to consider the fact that my work must be seen and appear in perfect condition even from a great distance.

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20 minutes ago, Tama Suki said:

I would love to follow you inworld, with your permission, and have some small talk there when you have time.

I'd love to but I haven't actually logged on to Second Life for several months now and there's not much chance I will be able to anytime soon. I've got a lot of RL and a build project way too big for SL taking up all my time these days.

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@Tama SukiBasically, Draw distance is how far the SL environment around you extends, while LOD Factor affects the visual solidity of objects at unspecified distances. They are both very different things and shouldn't be confused as being the same thing.

Draw Distance is the visible world - a sphere or bubble - surrounding your avatar's central point.  Imagine your draw distance is 128 metres.  This means all objects and avatars within 128 metres of your avatar's centre point will be drawn in all visible directions around you. This means those objects outside of this 128m will be ignored and will not be drawn.

Some objects may be so large that they may have their "root" (centre points) within your Draw Distance bubble, but these large objects (and others linked to them) may physically extend outwards of the Draw Distance bubble and these will be seen outside of the Draw Distance bubble into the distance.

Some useful Draw Distance advice; if you're inside an enclosed building or other narrow confined environment with solid walls and a ceiling, do you really need your Draw Distance to be drawing things outside the physical and visual range of your avatar?  The lower your draw distance is, the less work your computer needs to do and the higher your framerates will become.

LOD Factor, which stands for Level Of Detail concerns the visual solidity (not transparency) of detailed objects, such as prims, sculpts and meshes at distance. The higher the LOD,  the more solid they appear at greater distances.

A low LOD will result in detailed mesh objects looking deformed or even invisible at distance. SL's default LOD Factor is set to 1.25 (2.0 on Firestorm), while 4 is considered the maximum.... although it can be over-ridden to go even higher in the Debug Settings (RenderVolumeLODFactor), although this is not advisable to users with lower performing computers.

LOD Factor is perfectly acceptable on the default setting of 2. However 4 (maximum) gives better solidity at further distance.

 

Edited by SarahKB7 Koskinen
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3 hours ago, SarahKB7 Koskinen said:

A low LOD will result in detailed mesh objects looking deformed or even invisible at distance. SL's default LOD Factor is set to 1.25 (2.0 on Firestorm), while 4 is considered the maximum.... although it can be over-ridden to go even higher in the Debug Settings (RenderVolumeLODFactor), although this is not advisable to users with lower performing computers.

LOD Factor is perfectly acceptable on the default setting of 2. However 4 (maximum) gives better solidity at further distance.

The problem with that is, as you say, that not everybody in SL has computers strong enough to handle those high LoD factors. There isn't really such a thing as "better" LoD, it's either good or bad, nothing in between. Well, maybe there's a little bit of leeway but not much and of course, there's also a question of monitor size. But essentially, if the LoD isn't good enough for everybody in SL, it isn't good enough for SL.

In other words, if we make the LoD strong enough that a newcomer running the official viewer on mid graphics on a mid priced laptop can enjoy the SL experience at all, there's no need for anybody to increase their LoD factor very much beyond what they are running with. Better to use whatever extra power your computer has to crank up some of the other graphics settings.

There is such a thing as "too good" LoD though. When the LoD is so strong (either through excessive LoD factor or by meshes with over-strengthened LoD models) the viewer is sruggling to find room for all the tris on the limited number of pixels on the screen, even the strongest GPU in the world will have a hard time rendering the scene.

Edited by ChinRey
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Since I was granted an entire sim with 2k / 5k Land Impact available to work (The SLEA guys are magnificent) I had set my mind to build a structure that, seen from far away as a whole, could have its own design very significant.
At this point, however, I believe that I will have to structure the situation in this way. The project viewed from far away will have to be built with simple SL prims, everything else can be created in mesh.
Draw Distance is not important in my opinion also because it is a thing known by most of the citizens, so I did not mention it.
LoD factor, I think I will work with the viewer set to 1.25 which is the standard of the official viewer.

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13 hours ago, Quarrel Kukulcan said:

Anything too far away simply isn't drawn, and how far is "too far" is different for each resident depending on their viewer graphics settings.

dd.jpg

For me it is important to know how the default viewer is set when a new account opens it for the first time.
I don't think it's set at 64 draw distance.

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3 hours ago, Tama Suki said:

I don't think it's set at 64 draw distance.

It's usually set according to the graphics quality slider, anything at or above high gives you something like 128 metres. 64 is the minimum in he official viewer and a few of the TPVs. Other TPVs will let you go lower to 32 or even less if you want to see what myopia is really like in RL.

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I meant that when a new account is created it will see SL with default settings.
When a noob enters the world for his first time he has no idea that there is a menu with many small buttons and sliders to change things he has never heard of in his life.

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1 hour ago, Tama Suki said:

I meant that when a new account is created it will see SL with default settings.
When a noob enters the world for his first time he has no idea that there is a menu with many small buttons and sliders to change things he has never heard of in his life.

You can safely assume 128 meters.

 

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3 hours ago, Tama Suki said:

I meant that when a new account is created it will see SL with default settings.

Not just a new account; if you install a different viewer, or change your graphics card, the first login will throw up a message box advising that graphics have been set to the recommended settings.

128 metres is actually sensible for newcomers, in a full region they will see most of it with none of the popping in and out of view that will occur when draw distance is at 64 metres. Once they learn about the settings they can play around, s small parcel such as their first Linden home will run fine at 64 metres, I find 96 metres is the best compromise for me given the size of parcels I typically visit.

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