Why Would a Mesh Tree Be 800+ Prims?

[Prokofy Neva]

I recently bought a forest skybox for only $199 which is nice enough but -- as the creator admitted in her MP ad -- the tree in it is a whopping 800+ prims. Wow! 

And I have to wonder WHY.

It's not as if every twig and leaf is a separate detail.

I tried turning it to convex hull -- that didn't work. It did not the amount of prims. Actually, I wonder if any mesh can be started/left on "prims" and that it doesn't HAVE to be put on "convex" -- but this made no difference any way.

Worse, turning on convex hull makes it impossible to walk into the tree house area -- that's always the downside unless you do it right, I often come across this in houses and have to ask the creator to re-do them.

I took the top leaves off the tree and got it down only to 500+.

Since now there are only some bare trunks and branches, I have to wonder WHY.

I have to wonder if this is just made badly, and maybe there's a way to make and/or upload mesh so that it doesn't have 800 prims like this.

If anyone wants to see inworld, IM me.

I may live with it, but it's a LOT of prims!

[Fionalein]

Just a wild guess into the blue (cannot do more without seeing it): Maybe it is the opposite of bad LOD mesh - no LOD reduction at all. If you try looking at it with the new FS tools for viewing different LOD models is there any reduction happening?

Edited June 17, 2018 by Fionalein

[Chic Aeon]

Without some screenshots we can't really advise. Could be a few things including trees from the "sapling" generator in Blender which can produce some outrageously high land impact trees. It was not meant to be a GAME ASSET TREE GENERATOR at all LOL.  The other things could be the physics cost.  

As Fionalein said the new Firestorm tools will tell you more and it is a good thing for consumers to learn their way around. 

Even the "more info" button in the build tools will tell you where the major cost is ---- download or physcis. 

Post I did on the building tools. Should be understandable to non-mesh makers :D.

https://chicatphilsplace.blogspot.com/2018/02/the-new-firestorm-building-and-shopping.html

 

 

[Whirly Fizzle]

Can you PM/IM me a link to the MP listing for that skybox?

[Prokofy Neva]

4 hours ago, Chic Aeon said:

Without some screenshots we can't really advise. Could be a few things including trees from the "sapling" generator in Blender which can produce some outrageously high land impact trees. It was not meant to be a GAME ASSET TREE GENERATOR at all LOL.  The other things could be the physics cost.  

As Fionalein said the new Firestorm tools will tell you more and it is a good thing for consumers to learn their way around. 

Even the "more info" button in the build tools will tell you where the major cost is ---- download or physcis. 

Post I did on the building tools. Should be understandable to non-mesh makers :D.

https://chicatphilsplace.blogspot.com/2018/02/the-new-firestorm-building-and-shopping.html

 

 

I will not be using Firestorm for all kinds of reasons.

And I should NOT have to use Firestorm to understand a problem.

BTW, this is not about the way it looks or LOD as such -- I know to put that slider at 4.25 and that's not the issue, it's the land impact.

If that tool shows you where the cost is "download or physics," great, then maybe I can get this creator to re-do her tree and she'll sell more of them? If she cares.

I don't think she does, as her store is no more.

Whirly, I will send you the link, thanks. I think I will deploy it inworld where I have some prims, and see if I can replace the tree. It's a nice build otherwise.

BTW Chin Rey has a notecard explaining why land impact jumps up and how to cure it, and I sent it to that maker just in case it makes a difference although they may no longer log in.

 

 

Edited June 18, 2018 by Prokofy Neva

[Alwin Alcott]

4 hours ago, Prokofy Neva said:

BTW, this is not about the way it looks or LOD as such -- I know to put that slider at 4.25 and that's not the issue, it's the land impact.

even i as total mesh build noob.... it's not about your slider in this situation.

 LOD is also the factor it gets from a creator during optimising the object in the creation process before upload

i'm sure builders can explain it better.

[OptimoMaximo]

To me, the problem is from the uploader itself and its assumption that Low and Lowest LoDs should be just a few triangles or, even better, an impostor which means a plane with the object image on it (again, few triangles), and every single triangle on top of that threshold is severely punished. It wouldn't even be a really big problem if the uploader wouldn't also claim the same geometry to be within the materials/geometry subsets of the previous/higher LoDs. I mean, if the the uploader would accept a different model for the two low LoDs, it would be easier and certainly more efficient/effective. However not all models can be treated this way, so a complex tree with planes as its foliage either simply shows bad LoD decay or an obvious model switch from a distance. Which is obviously frowned upon.

I hope that the new Animesh LoDs thresholds would be implemented for all items types, and perhaps also allowing different models to be loaded into the low LoDs slots without the need to have them in the higher levels.

[Whirly Fizzle]

Info for the tree:

 

 

[ChinRey]

50 minutes ago, Whirly Fizzle said:

Info for the tree:

Ah, that explains it. Way too many triangles lumped up in a single huge mesh. The creator could have reduced the land impact to a fraction by splitting that big trunk mesh into several smaller parts, probably also get rid of half the triangles.

Judging by the triangle numbers, the tree has probably also been a victim of LoD butchery but that doesn't matter since the LoD models will hardly ever actually be used for a mesh of this size - it's the high model all the way to the draw distance.

With that being said, the tree shouldn't actually be too heavy to handle neither for the server, the client or the connection lines, it's mainly a victim of the not very well thought out land impact forumla. It's hardly a well made mesh but I've certainly seen worse lag monsters with much lower land impacts.

Edited June 18, 2018 by ChinRey

[Whirly Fizzle]

I'm a total noob when it comes to mesh creation.
This tree increases in LI the larger you scale it. At a smaller, normal tree size, this mesh has a reasonable LI.

Am I right in thinking that if the creator had used "analyse" when uploading, this mesh wouldn't explode in LI when it was scaled larger?

[ChinRey]

25 minutes ago, Whirly Fizzle said:

Am I right in thinking that if the creator had used "analyse" when uploading, this mesh wouldn't explode in LI when it was scaled larger?

No. Analyze is all about the physics model and that is not relevant here, it's all about the download weight, that is a crude and inexact estimate of the amount of data that needs to be transferred.

A relatively simple explanation: The basic download weight is calculated separately for each LoD model and then added up. The weight for each model is based on the amount of compressed data it uses and how large an area it will be visible across with LoD factor set to 1 and draw distance 128 m. That means for a small mesh, you can afford to have a lot of triangles and vertices in the high model since it will only be used for closeup view while on a larger mesh, the high model will be used at longer distances so the complexity of the high model becomes increasingly more significant. With a mesh as big as this group of trunks, the entire high model wil have to be downloaded even if the tree is only going to be a small dot far in the distance and that of course increases the download weight significantly.

[Prokofy Neva]

On 6/18/2018 at 1:49 AM, Alwin Alcott said:

even i as total mesh build noob.... it's not about your slider in this situation.

 LOD is also the factor it gets from a creator during optimising the object in the creation process before upload

i'm sure builders can explain it better.

Yeah, I know all that. 

Whenever you bring up an issue, some people automatically tell you to fix this LOD thing. It's really meant for sculpties and not mesh, yet people tell you about it even regarding mesh. It's like people telling you to clear cache. It seldom is relevant.

[Prokofy Neva]

On 6/18/2018 at 5:57 PM, Whirly Fizzle said:

I'm a total noob when it comes to mesh creation.
This tree increases in LI the larger you scale it. At a smaller, normal tree size, this mesh has a reasonable LI.

Am I right in thinking that if the creator had used "analyse" when uploading, this mesh wouldn't explode in LI when it was scaled larger?

This creator isn't answering IMs and may no longer be active but you're right, one easy thing to do is just shrink it down, and just shrinking say by 30% already shaves off about 200 prims.

[Kyrah Abattoir]

Lod switching thresholds. 150 and then 576 meters.

Ouch.

Edited June 24, 2018 by Kyrah Abattoir

[ChinRey]

1 hour ago, Kyrah Abattoir said:

Lod switching thresholds. 150 and then 576 meters.

That's for the mid and low models. Fs doesn't even bother to calculate the hypotetical switch distance to lowest (it would have been more than 2,000 m).

There are a few occasions when it makes sense to make a mesh that way and a few others when it can't be avoided. This is not one of them.

Nor is a certain crystal skybox currently discussed in another thread but that is part of the explanation why it can happen at all: when the content creators employed by LL are prone to make such fundamental mistakes, how can we expect the average builder to do better? It's a good thing those two discussions came up on the forums at the same time because between them they highlight something I've been trying to plug over and over and over again here: if Linden Lab really wants to encourage more efficient content, they have to lead by example.

Edited June 24, 2018 by ChinRey

[Chic Aeon]

On 6/20/2018 at 8:28 PM, Prokofy Neva said:

This creator isn't answering IMs and may no longer be active but you're right, one easy thing to do is just shrink it down, and just shrinking say by 30% already shaves off about 200 prims.

Since none of the "smart folks" answered you so far I did a little test as I really didn't know the answer. I almost always use cube physics and analyse mostly because LONG LONG ago Drongle said to.  The simple answer is NO.

This is the ONE PIECE main build (no windows or door) from a recent upload. Default size

This is the same building enlarged some. You can see that the land impact goes up on analyzed also.  The PHYSICS part of the three areas remains the same in both.  This is also a good example (not pretty but still) of the improvement in my textures from the help of @OptimoMaximo

 

I just realized after coming back to this (company so didn't get posted when I wrote it) that the reason (I think) for the increased land impact is that the LODS switch at a much different place.  I notice this all the time of course but forgot to mention.  

IF I had made the house that much bigger and uploaded THAT size rather than the smaller size, I would have made different choices in the LOD files -- since no one needs to see that much a sim and a half away . 

 

 

Edited June 24, 2018 by Chic Aeon

[ChinRey]

2 hours ago, Chic Aeon said:

This is the same building enlarged some. You can see that the land impact goes up on analyzed also.  The PHYSICS part of the three areas remains the same in both.

That is an important point to remember: download weight, server weight and physics weight are completely independent of each other and calculated by wlidly different formulaes and it's only the largest of the three that counts towards the land impact.

The physics model only matters to the physics weight and wil not affect the land impact as long as it's lwoer than the download weight , as in this case.