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How to achieve very low LI with complex objects?


npcee
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Last year I finally decided to deal with my 2020 new-year resolution of learning how to use blender before it was too late and I can say Im completely addicted now. One of the areas that I decided to pay more attention was in making my objects not too demanding for the servers, because like many of you, I reeeeally hate lag.

So in my learning curve I started with simple objects, then I dipped my toes in learning to proper uv-unwrap things, getting the right sized textures for each part, being more conservative in my geometry to get the tris down, then I moved on to making my own LODs, using smooth normals so I dont need to rely heavily on bevels, making my own physics, etc, etc...

Everything was going fine and I was very happy with my progress until I saw something and my mesh-world came crashing down (oh, the drama, lol). The image attached is of a chandelier I saw recently in an event with more than 120 thousand vertices, good LODs (I was able to zoom out a bit without losing too much detail) but still only 4 LI.

One of the projects I made while learning was a backdrop that I gifted to a friend, and in this backdrop I also had a chandelier. And just like in the picture, coincidentally my chandelier used a very similar geometry (8-sided prims linked in an array then array'ed again around the main structure, simulating the chandelier crystals) which is why I got so obsessed with it. My backdrop however had more than 40 LI (despite having a lower number of tris), and Im pretty sure my chandelier alone was responsible for 80% of that.

So, after this wall of text, my question is... how? Are you guys hiding the good hacks from us? (lol) How come I see things with less than half the tris but double the LI of that chandelier? Is blender maybe not as good as those industry-standard softwares people use? Am I forgetting to uncheck the "double my LI" box when I upload stuff to SL?

 

 

unknown.png.547153742ba9a5370deb55fe31525cb5.png

Edited by npcee
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40 textures, 118 MB texture mem. 156 MB VRam...🤪

The LI part is easy. It's just a matter of reducing the lowest LODs drastically enough. Easiest done with some impostor planes with a projection of the model as the lowest LOD.

 

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The size of the object determines which LOD is the "most impactful" for the object's LI. I know of a thread with graphs demonstrating the size/LOD ratio, but it's old and tedious to find. It's pretty easy to guess, since for most objects it's the low/lowest LOD, unless you're making big vehicles, buildings, and such.

Besides that, you've probably noticed that there are three different costs for an object -- Download, Physics, and Server. The final land impact will be equal to the highest of those three costs.

That particular chandelier is awfully made from a technical standpoint, though.

Edited by Wulfie Reanimator
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18 minutes ago, arton Rotaru said:

40 textures, 118 MB texture mem. 156 MB VRam...🤪

Yeeeah... although I give props to the creator for making a really beautiful piece, when I saw the vram I thought it was almost a crime it only got 4 LI.

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8 hours ago, npcee said:

Are you guys hiding the good hacks from us? (lol)

Not on purpose but there isn't really a place to collect them all and Linden Lab doesn't seem to care much so it's all up to us volunteers. I've been trying to repost my own contributions from the forum to my Builders' Manual blog but I'm struggling to find all those old posts myself and it's quite a bit of work editing and reposting.

So far I've reposted two LoD related tuotrials. The first one is probably a bit too simple for you but it should give some ideas about the basics of curve simplification: https://chinrey.blogspot.com/2019/09/creating-lod-models-case-study-1.html

The second one is a bit more advanced and long enough it's split into seven lessons, starting here: https://chinrey.blogspot.com/2021/01/creating-lod-models-case-study-2-lesson.html

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To the OP it would probably be good to block out the name of the maker of the object you are showing since unless we are raving how good it is (and this really isn't from a technical standpoint) we are not suppose to NAME the person making it (unless it is US of course :D).

 

What would be better to do here would be to show us YOUR chandelier and the LOD settings from the FS build menu if you have that -- and the object inspection pane and we could probably tell you how to do better.   Even items that only cost 1 LI can be so triangle heavy that it is very very SAD so land impact is NOT indicative of a good build.  There are many ways to get "better" LODs and many choices to be made including just WHO you are building for :D.    Nothing is a secret. If you read through all or even just many of these mesh forum posts you can learn a ton. That is pretty much all I did when I started making mesh. Sometimes I didn't understand what they were saying but I read them anyway (not the clothing ones though :D).   

 

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14 minutes ago, Chic Aeon said:

Even items that only cost 1 LI can be so triangle heavy that it is very very SAD so land impact is NOT indicative of a good build.

Yes but that is not because the land impact calculation is wrong, it's because people - builders, regular users and the Lindens alike - (ab)use the LoD system in ways the long gone Gods of Second Life didn't intend to.

I mentioned it briefly in that long seven lesson tutorial I linked to but maybe I should emphasise it here: It's the mid - and sometimes even the low - LoD model that is supposed to be the main one, not the full detailed high one! Except for very big objects of course but they are hardly ever high poly anyway (if they are, the builder really, really ought to re-evaluate the way they build). From that perspective it makes perfect sense to allow for lots of tris in the high LoD model. They are only downloaded and rendered when you cam up clsoe to really examine and admire the object and when you do, it does no harm since there isn't much space on the screen for other things to be rendered anyway. The problem only arises when people crank up their LoD factor so all those tris are also rendered as part of a bigger scene.

Unfortunately it is not possible to calculate a realistic land impact of an object when one of the biggest factors, the LoD swap distance, is an unknown. Linden Lab made a huge mistake when they implemented LoD factor as a viewer setting. It should have been set for each object individually and the land impact calculation should have taken it into account. By now the mistake is so deeply ingrained both in the software and in people's habit there is no real chance it can ever be fixed.

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15 hours ago, Wulfie Reanimator said:

The size of the object determines which LOD is the "most impactful" for the object's LI. I know of a thread with graphs demonstrating the size/LOD ratio, but it's old and tedious to find. It's pretty easy to guess, since for most objects it's the low/lowest LOD, unless you're making big vehicles, buildings, and such.

Besides that, you've probably noticed that there are three different costs for an object -- Download, Physics, and Server. The final land impact will be equal to the highest of those three costs.

That particular chandelier is awfully made from a technical standpoint, though.

Are you able to tell me why that is awfully made?

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16 minutes ago, Liramaril said:

Are you able to tell me why that is awfully made?

I think what Wulfie didn't believe it was possible to make something as eleaborate as that at 4 LI without serioulsy butchering the LoD models and/or that the polycount is much higher than it should have been. I tend to agree with both but I won't say for sure without seeing the actual model first.

Texturing is definitely bad though. 39 1024x1024s and one 256x256 is waaaaaaaay too much!

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16 hours ago, npcee said:

So, after this wall of text, my question is... how? Are you guys hiding the good hacks from us?

One more reply, I found this:

https://community.secondlife.com/forums/topic/424186-one-texture-environment-in-unreal-modular-textures-in-realtime-3d-art/?tab=comments#comment-1764606

Some arrogant Linden who's never done anything himself to help wannabe builders sort out mesh (and wouldn't recognize good mesh if it bit him on the leg anyway) was mansplaining about how he knew everything about mesh and how us users never did anything to help. So I got a teeny bit annoyed and made a list of some of my own tutorial/assistance posts.

Those are only my posts though - and it's an outdated list as well. There is much, much more hints and tips from others to be found if you have the stamina too search through the forum archive.

Edited by ChinRey
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6 hours ago, Liramaril said:

Are you able to tell me why that is awfully made?

40 textures in an object with so much repeating geometry that you could get more resolution from one texture with proper UVs.

Almost all of those textures are 1024x1024, based on Tmem. Absolutely unnecessary.

With that in mind, I'm assuming but 98% confident that the lower LODs are not hand-made and that the chandelier won't be seen from across the room without increased LOD factor.

The triangle count is a lot harder to curb because of the nature of the object, so I won't rag on that.

Edited by Wulfie Reanimator
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What helped me: Take courses in retopology. There's a good one by Medhue that's free, and many others. It's not just for avatar attachments, and really does bang the concepts into the brain. Lots of techniques, learn as many as you can. Short answer: even quads throughout your model, no unnecessary verts to make the shape, structure it in such a way that you could reduce topology to very very little and still keep the same UV map. The retopo concepts are the same in any 3D modeling software, so the courses could be for Blender, Max or Maya. I've used all three and like Blender better, but each of us have different brains. 

And if you want to move to the next level - bake the detail from the high poly version to the low poly version to make a normal map you can put in the bump slot in the Texture tab. A 512 for the diffuse texture and another 512 for the normal map gives you more apparent detail than a 1024, for half the viewer side cost. Clever UV mapping will allow you to use one of each for the entire chandelier. 

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1 hour ago, Ada Radius said:

And if you want to move to the next level - bake the detail from the high poly version to the low poly version to make a normal map you can put in the bump slot in the Texture tab. A 512 for the diffuse texture and another 512 for the normal map gives you more apparent detail than a 1024, for half the viewer side cost. Clever UV mapping will allow you to use one of each for the entire chandelier. 

Not an argument but want to make sure that folks using normal map to "replace" topology understand that not everyone SEES materials.   "I" would (and am :D) more in favor of baking the ambient shadows and displacement (if used) into the diffuse texture.   All a choice of course but one folks should think about before deciding on their method.   I have seen some really horrible examples of how bad things can look if people rely on normal maps especially :D.     

I still don't think this light example beats the 1024 texture for the "head" of the match one :D.   

********************

It is also important to TEST.   This is the low LOD version of baskets I made last night. There is a high version also. But even at the lowest FS LOD setting the chart says 11 meters which is certainly enough for an inside item in most cases. 

 

image.thumb.png.74886682cf06948d5e469cf0ca3b0a4a.png

 

When TESTING it appears that the actual distance is even further than the chart suggests. 

image.thumb.png.c279eca575623d0ce60dfe732d422dbd.png

Screenshot at the distance these are visible at the lowest FS LOD setting. 

 

And no, I don't make my own LODs or at least very seldom. And no I don't think I do the best job that can be done --- just "reasonable".   :SwingingFriends:

We all make our choices.   One 1024 map, no materials. 

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16 minutes ago, Chic Aeon said:

Not an argument but want to make sure that folks using normal map to "replace" topology understand that not everyone SEES materials.   "I" would (and am :D) more in favor of baking the ambient shadows and displacement (if used) into the diffuse texture.   All a choice of course but one folks should think about before deciding on their method.   I have seen some really horrible examples of how bad things can look if people rely on normal maps especially :D.     

 

This is my rationale too for trying to get the model without materials selected as close to its presentation for those who run on higher settings! It bothers me to conceive of people walking around and seeing my thing looking gammy as hell XD

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On 1/15/2021 at 8:39 PM, Chic Aeon said:

Not an argument but want to make sure that folks using normal map to "replace" topology understand that not everyone SEES materials.   "I" would (and am :D) more in favor of baking the ambient shadows and displacement (if used) into the diffuse texture.   All a choice of course but one folks should think about before deciding on their method.   I have seen some really horrible examples of how bad things can look if people rely on normal maps especially :D.

I think I already scolded you about this before, but if someone's hardware can't render shadows, it typically also doesn't come with much ram either to store all those extra textures. You keep telling people to trade one for the other when low end hardware can't handle either anyway.

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158MB of VRam what in the *****...

But yeah... LI in second life is heavily influenced by the LODs. a common hack people do to save LIs at the expense of lower spec machines is to simply put a single triangle as their lowest LOD and nothing else. So an LI of 50 suddenly drops to four or two. You can further reduce the LI by simply not having a collision at all.

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7 hours ago, Cyrule Adder said:

158MB of VRam what in the *****...

That's all to common in SL unfortunately. The texture load we see in some sims is just mind boggling. One of the LL developers once compared the content load in SL to a DDOS attack.

 

7 hours ago, Cyrule Adder said:

a common hack people do to save LIs at the expense of lower spec machines is to simply put a single triangle as their lowest LOD and nothing else.

It's what we call LoD butchery. There is a "sweet spot" somewhere between 12 and about 35 tris depending on the object's geometry. Once you get down to that spot, there's nothing whatsoever in terms of LI and hardly anything in terms of lag to gain from reducing further.

Unfortunately it seems many, maybe even most, SL mesh makers have no clue whatsoever about LoD. They don't know what it is, what purpose it has or how to handle it effectively.

This 1 LI obsession often goes too far anyway. Look at Bellisseria. The Moles don't know how to handle LoD either but they make the opposite - and less destructive - mistake; they don't simplify their LoD models enough, adding a lot of unneccessary lag and LI but at least avoiding those horrible collapsed meshes. But even with those bloated LI figures, they can still fill up a sim with all the content it needs to look good. With properly optimized mesh it is never ever neccessary to spend more than 2,000 LI on a sim and usually you need much less. That is not including breedables, animesh, prim babies and such - they often need a bit extra - but you can't have that many in a sim before you get serious performance issues anyway.

Edited by ChinRey
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  • 2 weeks later...
On 1/15/2021 at 5:58 PM, Ada Radius said:

And if you want to move to the next level - bake the detail from the high poly version to the low poly version to make a normal map you can put in the bump slot in the Texture tab. A 512 for the diffuse texture and another 512 for the normal map gives you more apparent detail than a 1024, for half the viewer side cost. Clever UV mapping will allow you to use one of each for the entire chandelier. 

I have seen mentions of Blender tools which do this, most recently this free one. I've never used it. so I don't know how well it works, but it gets so frustrating when somebody says something like this without any pointer to a method, not even a link to a relevant page in the Blender documentation.

https://github.com/SavMartin/TexTools-Blender/

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5 hours ago, arabellajones said:

I have seen mentions of Blender tools which do this, most recently this free one. I've never used it. so I don't know how well it works, but it gets so frustrating when somebody says something like this without any pointer to a method, not even a link to a relevant page in the Blender documentation.

https://github.com/SavMartin/TexTools-Blender/

I would recommend to search YT for High to lowpoly normal map baking in Blender 2.x to get a basic idea of how it's done.  It requires some practice, and some knowledge to get decent results.

The clever part in "clever UV mapping" is still up to the artist being clever at it. Plugins like TexTools are just some helpers to make common tasks simpler. (I only know TexTools for 3ds Max, so I don't know what TexTools for Blender can do these days.) But it's not required to bake normal maps in Blender, nor to being clever at UV mapping.
The only thing I pretty much use in TexTools, in Max, are the texel density tools.

For a final normal map bake I would strongly recommend XNormal (with the UnityTSpace plugin), or Handplane Baker with the Unity tangent space. Both of these Bakers are free, but they are for Windows only.

Edited by arton Rotaru
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