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Mesh picture comparison and land impact


Sonielf Zinner
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Hello everyone, Im new to this forum, sorry if my question had been posted before.

 

During past days, i been building and testing diferente ways to upload a object to SL. And noticed, even my mesh have few vértices and faces, it still have more land impact than other objects who has more vértices. In this attached pics have 2 objects.

The Fence-mesh.png and fence.png is the object i create. Has land impact 4.

The Sim-mesh.png and sim.png is a object I saw in a sim. It has more details than my mesh, but lower land impact.

 

Is this some upload options Im missing? I didnt upload physic for fence.

 

 

Fence-Mesh.png

Fence.png

Sim.png

Sim-Mesh.png

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1 hour ago, Pamela Galli said:

The LOD and/or size contribute to LI.

If I remember correctly, so doesthe complexity of the physics or hitbox...

Back a few years ago when mesh was new the boating types quickly found that the physics had some of the largest impact on LI.

Did you make a nice simple plain rectilinear box for the physics on those balustrades?
 

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36 minutes ago, Klytyna said:

If I remember correctly, so doesthe complexity of the physics or hitbox...

Back a few years ago when mesh was new the boating types quickly found that the physics had some of the largest impact on LI.

Did you make a nice simple plain rectilinear box for the physics on those balustrades?
 

Yes, I did upload with a rectangle physic, and without physic too.

 

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Hard to say without knowing a few more details. Many mesh makers cheat, reducing the nominal land impact by butchering their LoD models. It's perfectly possible to make the staircase railing you saw inworld at 1 LI with proper LoD though and at the size it ahs there wouldn't be much to gain from LoD butchery anyway.

There are so many techniques to reduce the land impact of a mesh and there's really no room to list and explain them all in a message board post - we'd need a book for that.

I suggest you start by reading this post though. I have a sneaking suspicion you'll find the answer to this particular case there...

 

Edited by ChinRey
Typos again
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MUCH in the mesh boards on this. A seach for LOW LAND IMPACT MESH will likely find some of them

Simplistically there are THREE factors that contribute to land impact - Download, Physics and Server. To figure out what is making your mesh higher you need to look at which one is the highest in the uploader. And as ChinRey said the railing that has the low land impact in world could have horrible LODS (turn your LOD setting down to 2 or below and see if it still looks good at a fair distance). 

So some research or more info will probably help out. 

It IS a big and COMPLEX issue but one that mesh makers need to be aware of -- so now you are!  That's a big part of learning. 

 

 

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I’m with Pamela on this on.  Its  LOD’s.

When you are close to an object you can see all of its detail. Lots of vertices and triangles need to be calculated and rendered on your screen. When the object is farther away you cannot see so much detail so it would be a waste of processing power to still have to calculate the positions or all those triangles.

What many game engines do, including Second Life is to use different mesh models depending on their distance from the viewer. A High detail model when viewed up close. Switching to a Medium detailed model when viewed a little farther away. A Low poly model when it is still farther away. A Lowest poly mesh when it is so far away you can’t make out hardly any details at all.

 

 

These meshes of different complexity are called LOD’s.     Level of Detail.

The distance at which one LOD mesh switches to another is dependant on its size. (and the value you have the RenderVolumeLODFactor set at in the viewer that you are using).

A large mesh model like a house will switch LOD’s at a greater distance than say a flower vase.

A mesh object in Second Life really is a collection of 5 different mesh models.

High LOD mesh.

Medium LOD mesh.

Low LOD mesh.

Lowest LOD mesh.

Physics mesh.

You have created your Fence mesh and saved it as Fence.dae. This is the High LOD mesh. And you have your Cube.dae to use as your Physics mesh.  That’s only 2 meshes!

Oh I forgot to mention the most important thing …….

The complexity of the lower LOD meshes has a huge effect on the final LI cost of the object.

For room size objects it will be the Medium LOD mesh that has most effect.

For a flower vase size object it will be the Lowest LOD mesh that has most effect on LI .

For your Fence its probably the Low LoD that effects the final LI cost the most.

The more complex your Low LoD mesh is the higher will be the LI .

The fewer Vertices/triangles used in that Low Lod mesh the lower will be the cost.

So what about the other 3 LOD meshes?  If you are only loading up your Fence.dae and Cube.dae then hitting the Calculate weights and fees button, then it is the Uploader that is creating these other 3 lower LOD meshes for you. These are Automatically Generated for you. See first screenshot below :

 

 

LODs.png.493157304a3ee821326241b43beebaac.png

 

If you look more closely you can manually change the complexity of those Auto Generate lower LOD meshes and set the vertice and triangle count to a lower number.

In the second screenshot I have set all three  Generate lower LODs to there minimum values. Notice in the Preview window that the Medium LOD mesh now appears as a single Triangle. The LI count is now only 1.6 .

 

LODs2.png.5989b512fea058b4fac5c425122d5122.png

This is certainly a big difference from the  first screenshot but if I were to upload like this when I zoom out all I will see of my beautiful mesh is a single triangle !

 

This is what Chinrey calls Butchering the LOD's :)

OK low LI but not very good to look at from any distance other than close up.

Instead of using Auto Generated lower LOD’s a much better solution is to create them yourself and and use these in the lower LOD slots of the Uploader.

But when just starting out most people don’t,  they play with the auto generate values :)

The Auto generated LOD’s can never be as good as the ones you make yourself. The auto generator just cannot know what details are important to keep and which can be removed for each level of detail.

One thing you need to remember when creating your own LOD meshes is that each LOD mesh must have the same list of material faces.

As you gain experience you will get the feel for which LOD level is going to have the most impact on LI and also how much detail you need  in each LOD model.

 

Edited by Aquila Kytori
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32 minutes ago, Aquila Kytori said:

Instead of using Auto Generated lower LOD’s a much better solution is to create them yourself and and use these in the lower LOD slots of the Uploader.

That's a good explanation, Aquila but although I don't know, in this particular case I have a feeling it might be the server weight that is the one that determines the LI. How many separate meshes is that balustrade made from?

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1 hour ago, Aquila Kytori said:

annother OOOOOOOps, I jumped in without really looking carefully at the screenshots.

That makes two of us. Looking closer, it's hard to see how that build could be split to give 4 download weight, Three or five, yes but not four.

So, if the physics weight is ok, it's back to that old download weight again.

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