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Why does (some) mesh do this?

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On 12/8/2018 at 3:12 PM, Kyrah Abattoir said:

I noticed that quite a few creators who use Blender don't actually appear to know about smooth shading...

Quite a few furnitures I bought where, on close inspection, all the polygons are "faceted" like that.

On top of being ugly it actually is slower to render.

Not understanding smoothing in the external app is one cause but a lot/some of the time it is because they erroneously use the "generate normals" option in the uploader which is guaranteed to mess up your nice smooth shading. Often people do this because it has a small impact on the LI (because the resultant mesh compressed a little more when zipped). I've even seen people recommend it as a default step!

I've not considered the render speed aspect before, I'm not convinced it makes much if any difference, but not having looked at it I won't rush to any conclusion.

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On 5/17/2017 at 7:03 PM, arton Rotaru said:
On 5/17/2017 at 6:18 PM, Bitsy Buccaneer said:

I *thought* worn, rigged mesh stayed a highest LoD

Worn rigged mesh uses the same LOD algorithm as any other object in Second Life. The only difference between worn rigged mesh and non rigged mesh is that the attachment uses the size of the entire avatar as its Bounding Box size to calculate swapping the LODs. So even some tiny jewelry will have the effective BB size of the avatar.

This can be quite handy when you, for example, create some full body armor out of several small pieces. You don't have to worry about inconsitent LOD swapps because of the different sizes of the meshes.

A couple of notes on this (Arton's post is the succinct version, this is a more detailed version). 

As Arton notes, rigged mesh LOD behaviours according to the same algorithm but it is affected by a couple of other things 1) the bounding box of the avatar 2) a bug that makes the effect of the bounding box even larger.

The algorithm/equation uses the radius of the bounding box to determine the size of the mesh and thus (in theory) how large it is in the context of your displayed scene. A big building is visible from half-way across the region but your earring is not. For rigged mesh (and notably only rigged mesh not unrigged worn mesh) the radius used is (supposedly) the avatar bounding box. This has good and bad effects, on one hand it means that all your attachments LOD decay at the same rate (as Arton points out this stops things like your panties vanishing before your dress) but on the other hand it means that all your attachments LOD decay at the same rate 🙂 (so your pinky ring is displayed in all its overly detailed high poly glory for exactly as long as your body is despite them being vastly different sizes.

But it is worse than that, I reported a bug a while back whereby the radius used for the avatar is not the radius at all but the diameter meaning that the LOD decay rate is half what it ought to be (or in other words, that pinky ring lags you out for twice as long as it ought to). See https://jira.secondlife.com/browse/BUG-40665 for more info

For #2, there is a further issue. because the bounding box of the mesh can be artificially extended by the way that some creators organise their meshes.  This is detailed in this Jira https://jira.secondlife.com/browse/BUG-214736

I should also note that the Animesh viewer release has changes that dynamically recalculate the bounding box. This can affect your rigged mesh LOD behaviour but because of the preceding points it is unlikely to do so for the majority of cases.

 

 

 

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10 hours ago, Beq Janus said:

Not understanding smoothing in the external app is one cause but a lot/some of the time it is because they erroneously use the "generate normals" option in the uploader which is guaranteed to mess up your nice smooth shading. Often people do this because it has a small impact on the LI (because the resultant mesh compressed a little more when zipped). I've even seen people recommend it as a default step!

I've not considered the render speed aspect before, I'm not convinced it makes much if any difference, but not having looked at it I won't rush to any conclusion.

It's probably not really noticeable but consider this:

  • To create a hard edge, the vertex is doubled up so each face can have a unique normal, 4 smooth shaded quads in a 2x2 grid use 9 vertices, 4 flat shaded quads will use 16.
  • More data so unless it's on purpose, you made your mesh heavier and uglier.
  • During the rendering process, the GPU will render a polystrip until it hits an uv seam, edge split, material change (it's a bit more complex but this is a simplified example).
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On 12/11/2018 at 4:24 PM, Beq Janus said:

This has good and bad effects, on one hand it means that all your attachments LOD decay at the same rate (as Arton points out this stops things like your panties vanishing before your dress)

Yes but prominent "covering" items like clothes (and house walls and roofs) should never be reduced down to invisibility anyway. There's hardly anything to gain from such a drastic reduction and the negative conseqences are rather serious.

Also, when done deliberately spreading the LoD swaps over time is a very effectie method to make them less noticeable and in theory at least (I haven't checked this) it should also be easier for the viewer to handle the LoD swaps one at a time than to do them all in one go.

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On 12/12/2018 at 4:42 PM, ChinRey said:

Yes but prominent "covering" items like clothes (and house walls and roofs) should never be reduced down to invisibility anyway. There's hardly anything to gain from such a drastic reduction and the negative conseqences are rather serious.

Also, when done deliberately spreading the LoD swaps over time is a very effectie method to make them less noticeable and in theory at least (I haven't checked this) it should also be easier for the viewer to handle the LoD swaps one at a time than to do them all in one go.

No argument here, but that is a creation problem, until people stop making clothes that vanish at medium LOD it remains an issue. As for spreading LOD swaps, the way that the viewer works it really doesn't make an awful lot of difference you'd be hard pushed to discern the benefit of that distinctly from the rendering cost reduction associated with a lower LOD. staggering the LOD swapping from a visual perspective "should" look better, insofar as items should swap when the onscreen resolution is low enough that the two models render very similarly, but as you know this relies on the efforts of the creator as well as getting the swapping algorithm right. My preference is actually to LOD swap based on screen space resolution, if you are rendering a high poly mesh into 5x5 pixels on screen then clearly the LOD swapping is not happening properly and in an ideal world the viewer ought to be able to work at least some of that out.

 

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