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For mesh making, what is most important: triangle count, land impact or complexity count?


Kechup Heinkel
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If you make an object with a large amount of triangles (several thousand for example) but it only has a land impact of 1 or 2, and it only raises your avatar complexity 500 - 2000 points when worn, is this acceptable? How should you measure or determine if your objects or wearables are lag friendly or not?

 

Edited by Kechup Heinkel
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Firstly: What do we mean by "lag?" For my post, I assume it to mean viewer framerate.

Complexity calculations are currently pretty demonstrably broken and LL is working(tm) on reforming it. Complexity should be ignored as a metric for mesh.

Land Impact is not really indicative of how heavy the mesh itself is. There are more factors at play.

What's important is the number of triangles, number of textures, and the size of those textures. The exact numbers are very subjective. A "couple thousand triangles" is not a lot, objectively, but if we were talking about 20K triangles for something like a single ring, that would be excessive and we'd call that laggy, because that amount of detail simply couldn't be seen from a normal distance. Same applies for 1024 resolution textures on any small item, or using 10+ (my subjective example) textures for an object.

Edited by Wulfie Reanimator
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I am not sure that "lag" can be defined as FPS rate. I can be in a newly opened busy event having DERENDERED all the other avatars (my first step when entering that kind of place) and have a goof FPS (like 50 and STILL not be able to move and have fubber-banding.  I am not sure what the correct definition of lag might be but I can't believe it is just FPS.   

 

In my mind TRIANGLES is what counts.  You can have a very complex object that is only one land impact and fairly good size and it can be WAAAAAAY too many triangles (many not needed - the creator is just being lazy OR downloading "render models" from an internet site. 

The best way to see what is going on is to inspect the object (this in Firestorm, not sure about other viewers. 

 

For example, this is a smallish decor item (.84 meters at the longest measurement).   It is 85,000 triangles.  You could make a very nice small house with the same amount of triangles :D.    So you need to judge the item by how large it is compared to how "heavy" it is in triangles (or vertices).    It is also texture heavy. 

 

It is OK to have one or two of these heavy items in an area, but when you start getting a cluster of them --- not good.  

 

image.png.a64f866c4ac3acd3b60d8f57fc6901f6.png

 

In comparison, here is a small but detailed house with a triangle count under 14,000

 

image.thumb.png.6c4ecf11472436e514d6148b0d78b7b6.png

 

Edited by Chic Aeon
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3 minutes ago, Chic Aeon said:

I am not sure that "lag" can be defined as FPS rate. I can be in a newly opened busy event having DERENDERED all the other avatars (my first step when entering that kind of place) and have a goof FPS (like 50 and STILL not be able to move and have fubber-banding.  I am not sure what the correct definition of lag might be but I can't believe it is just FPS.   

You're right, it's not just FPS. There are many kinds of lag, so defining what we're talking about is important or else we're all confused with different contexts.

The fact that you aren't able to move isn't something that can be fixed by optimized mesh. You can replace all the mesh with simple cubes (or derender them, as you did) and still be unable to move, because that kind of lag has a totally different cause.

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Ok. I never paid attention to triangles until recently, and have no idea how many is too many. I looked at the triangle counts in some of the mesh clothing I own for reference but I still don't know if they're using too many triangles or not. A lot of them range from 15,000 - 100,000 triangles. One of the dresses I have is 120,000 triangles, but it is quite detailed. I have a shirt that is about 30,000 triangles. I have shoes that are 60,000 triangles (highly detailed) and boots that are 15,000 (less detailed). A simple tank top that I own is 15,000 triangles.

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5 hours ago, Kechup Heinkel said:

Ok. I never paid attention to triangles until recently, and have no idea how many is too many. I looked at the triangle counts in some of the mesh clothing I own for reference but I still don't know if they're using too many triangles or not. A lot of them range from 15,000 - 100,000 triangles. One of the dresses I have is 120,000 triangles, but it is quite detailed. I have a shirt that is about 30,000 triangles. I have shoes that are 60,000 triangles (highly detailed) and boots that are 15,000 (less detailed). A simple tank top that I own is 15,000 triangles.

Do some tests of your own. Make test versions with different triangle counts and compare them on the beta grid. It should help you start to get a feel for where you can safely reduce triangles and where you need to have some extra. Make them count.

Also use wireframe view (Shift-CTRL-R) to look at the density of triangles. You want to be able to see through your object in wire frame. Look at other people's too.

Ask yourself how much geometry a detail needs or if it can be achieved through the texture.

The ideal number of tris is as few as you can manage without too big a hit to quality. It's a balancing act, often with a lot of compromises, and more of an art than an exactly science. Hence, test versions, trial and error and lots of practicing. You're asking good questions, but the answers can vary depending on what the item is and how it's used. What else might it be worn with or used around?

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3 hours ago, CoffeeDujour said:

Textures, despite all the the precious VRAM they use, are cheap.

Lets not get all upset over rezzed objects. It's not rezzed objects.

It's our avatars.

But avatars are "rezzed objects" too as far as the render engine is concerned. From that perspective there isn't really that much difference between them. Texture and vertice abuse is far more common for avatars than for other objects though.

 

14 hours ago, Kechup Heinkel said:

If you make an object with a large amount of triangles (several thousand for example) but it only has a land impact of 1 or 2, and it only raises your avatar complexity 500 - 2000 points when worn, is this acceptable?

When it comes to rezzed objects there is actually a direct relationship between the number of vertices and triangles and the land impact, it's just a little bit obscured by the LoD system.

Download weight, the factor that usually (but not always) determines the land impact, is based on the mesh' file size which again mainly depends on the number of triangles and vertices. What makes that relationship a bit ahrd to spot is that it takes all four LoD models into account, weighing their significance towards each other according to how often they are assumed to be displayed - or in other words how large an view area they cover.

There are several other factors that come into play but as a rule of thumb, expect 1 LI to signify an average number of actually displayed triangles to be 25 or less - up to around 30 in soem cases. That means that if a mesh has thousands of triangles and a land impact of 1, it's so small that hardly anybody will ever see the high LoD model anyway, all it does, is take up cheap storage space on the server. So you can load up the high model with tris to your heart's content with very little negative effect. The downside is of course, that no matter how much you elaborate your high LoD model for such items, nobody's ever going to see it and apreciate your hard work.

There are two kinds of driven content creators in Second Life. There are those who are obsessed with how their model looks and spend hours getting every little detail right and there are those who are really obsessed by how their model actually looks  - in SL - and spend hours getting the most relevant LoD models right.

Edited by ChinRey
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14 hours ago, Kechup Heinkel said:

Ok. I never paid attention to triangles until recently, and have no idea how many is too many. I looked at the triangle counts in some of the mesh clothing I own for reference but I still don't know if they're using too many triangles or not. A lot of them range from 15,000 - 100,000 triangles. One of the dresses I have is 120,000 triangles, but it is quite detailed. I have a shirt that is about 30,000 triangles. I have shoes that are 60,000 triangles (highly detailed) and boots that are 15,000 (less detailed). A simple tank top that I own is 15,000 triangles.

The numbers themselves are not really relevant, it depends how you use them, and different types of objects call for different approaches.

The big question is what is necessary versus what is superfluous. Why do you need that geometry? Does it matter? Can you notice its absense? And if yes, can anyone else?

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1 hour ago, Kyrah Abattoir said:

The numbers themselves are not really relevant, it depends how you use them, and different types of objects call for different approaches.

The big question is what is necessary versus what is superfluous. Why do you need that geometry? Does it matter? Can you notice its absense? And if yes, can anyone else?

That said, as a general rule when talking about something like avatar attachments... no single item you can wear should reach 100K triangles, not even mesh bodies. I base this opinion on the fact that other games can do even better with less, even when we afford some margin of leniency due to SL vs other renderers.

The earlier examples of 120K dress, 60K shoes, 15K T-shirt are almost certainly excessively detailed in terms of triangles. It is common for SL clothing creators to make the inner surfaces (facing the avatar's skin, impossible to view normally) solid, wasting rendering time for no practical reason. Removing those alone would almost halve the tri-count.

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13 hours ago, Wulfie Reanimator said:

Removing those alone would almost halve the tri-count.

Yeah it's not difficult to make "hole caps" that use much less geometry than a full outfit underside.

It's a shame that so much of the oldschool game modding tutorials are now gone. As games have gone fancier and fancier, a lot of the old informations from the half-life modding scene simply disappeared. And a lot of people now assume that something that's just textured rather than fully meshed is down to the artist's lazyness, when it is typically more involved to "suggest" details than actually detailing it.

It doesn't take a lot of work to cover a piece of industrial equipment with rivets, no one models rivets individually, it's all copy pasting. What does take work is to figure out how to get the same overal look and feel, without the rendering cost.

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