The 1 LI Mesh Challenge

[ChinRey]

Are you ready for it?

The rules are:

• Any kind of object made from a single mesh or two linked meshes.
• Land impact no more than 1.
• No more than 2 megapixels of textures, normal maps and specular maps (two 1024's or 8 512's or 32 256's or any combination that doesn't exceed 2,097,152 pixels).
• LoD good enough the object looks fine at any view distance up to 128 m with LoD factor set to 1. Include photos showing all the relevant LoD models.
• Appropriate physics - walkable surfaces (if there are any) must be fully walkable and it must be possible to rez on them. Any other surfaces must be solid so people can't walk through them (unless they are supposed to be phantom of course).
• Multiple entries is allowed but each must be a separate post.
• The winner is the entry with the most likes. However:
  • The challenge is protected by an anti-cheat jinx. Anybody who tries to bloat their own or their favorite's entires with alts is likely to end up suffering from hemorrhoids, poor internet connection and daily calls from tech support in India.
  • The challenger (that's me) may post a few entries herself but they are not part of the competition. (I still like likes though )

For the similar prim challenge, see https://community.secondlife.com/forums/topic/449221-the-1-li-prim-challenge/

 

Edited February 8, 2020 by ChinRey

[animats]

3 hours ago, ChinRey said:

LoD good enough the object looks fine at any view distance up to 128 m with LoD factor set to 1. Include photos showing all the relevant LoD models.

Yes.

I'd like to see some good vehicle wheels. The wheels are usually the first part of a vehicle to disappear.

They really do have wheels. You just have to get closer enough to see them. LOD factor 1.

Low LODs for wheels are easy, but not automatic. Take a picture of the high LOD and paste that onto a simple face as an impostor. Good wheels, especially spoked ones, tend to be complicated, and mesh-reducing them makes the spokes or struts disappear. At distance, a flat picture looks great.

There are hundreds of wheels for sale on Marketplace, but too many of them behave like this. Most can't be seen in world. (My apologies to the Lesbian Ranch, where I landed by following a "see item in world" link for a motorcycle wheel.)

[Wulfie Reanimator]

23 hours ago, animats said:

Low LODs for wheels are easy, but not automatic. Take a picture of the high LOD and paste that onto a simple face as an impostor. Good wheels, especially spoked ones, tend to be complicated, and mesh-reducing them makes the spokes or struts disappear. At distance, a flat picture looks great.

Like this? Took me about 90 mins to go from scratch to initial model to 1 LI, plus the time it would take me to properly UV unwrap and texture it. I'm not gonna do that, but I'd share the .blend file.

The underside of the rim-front-thingy doesn't have faces even in the highest LOD because you'll never see them from any proper angle. The back of the wheel is a pretty simple cone to a single vert. (Here's the highest and lowest LODs.)

This is how big the wheel can be in-world before going to 2 LI, and how far you can view it before it leaves the highest LOD:

Edited February 9, 2020 by Wulfie Reanimator

[Anna Nova]

On 2/8/2020 at 2:05 AM, ChinRey said:

• • ...  poor internet connection and daily calls from tech support in India.
  •  

 

So what's new?

[Wulfie Reanimator]

The tire was a fun example so I tried another more tricky "curvy" shape. It's a simple shape (about 50 mins from scratch to 1 LI with subsurf), but also 0.696 LI. No split edges or bevels but it still looks very smooth and sharp. Also note how I didn't remove any significant loops from the original subsurf for the highest LOD, but still reduced the tri count massively (from 1856 to 432). Anything that contributed to a curve stayed.

I'd also like to shout-out this gem from 2011, it still holds up: 

 

Edited February 12, 2020 by Wulfie Reanimator

[Wulfie Reanimator]

I was on a Netflix binge and did one more to do a properly complex object with many parts. Mainly based on this image. Unfortunately the radius for this mesh is so small that I just can't use more than 20 triangles on the lowest LOD and stay under 1 LI, so I couldn't make it anywhere near as clean as I wanted. 

With a lot of experimentation on LI results...

Edited February 14, 2020 by Wulfie Reanimator

[ChinRey]

On 2/14/2020 at 7:15 PM, Wulfie Reanimator said:

Unfortunately the radius for this mesh is so small that I just can't use more than 20 triangles on the lowest LOD and stay under 1 LI, so I couldn't make it anywhere near as clean as I wanted.

There is actually a trick to adjust the swap distances, add a loose vertice to increase the item's nominal size. For this vase I added on above the actual mesh, doubling its height:

 

You have to sort the vertices to make it no. 1 on the list. The uploader is supposed to delete all loose vertices but it has to keep no. 1 because it's the reference point for all vertice coordinates.

I think we should use the loose vertice extender a lot more. It may be a crude hack but so is SL's mesh LoD system and fighting fire with fire is fair.

Edited February 16, 2020 by ChinRey

[Wulfie Reanimator]

4 hours ago, ChinRey said:

You have to sort the vertices to make it no. 1 on the list. The uploader is suppsoed to delete all loose vertices but it has to keep no. 1 because it's the reference point for all vertice coordinates.

I think we should use the loose vertice extender a lot more. It may be a crude hack but so is SL's mesh LoD system and fighting fire with fire is fair.

That sounds really clever, but how do you "sort" the vertices? Can it be done in Blender or am I gonna have to edit the .dae by hand? Does it need to be done for all LODs or just one?

Edited February 15, 2020 by Wulfie Reanimator

[ChinRey]

4 hours ago, Wulfie Reanimator said:

Can it be done in Blender or am I gonna have to edit the .dae by hand?

Yes, it can be done in Blender. Position the 3D xcursor at the location fo the loose vertice, select all and sort elements by cursor distance.

Screenshot from Blender 2.78. I've been a bit slow to update my software recently.

You have to include the loose vertice in all LoD models or the object will change size and/or position at the LoD swap distances. Come to think of it, maybe that is something that could be used as an effect.

[ChinRey]

21 hours ago, Wulfie Reanimator said:

That sounds really clever...

Maybe I should post an example of this and one or two other tricks. Here's a stack of three tins of canned tomatoes.

 

They're in real life size so quite small by SL standards.

The texture is nothing fancy, a 256x128 for the label and a 128x128 for the top, both good old Linda Kellie ones.

Four cylinders with 24 curve resolution, that's 368 triangles unreduced. At this size (13.8x14.7x21 cm) the swap distance to lowest is less than 4 m which means it needs more than 40 triangles for the lowest model. That's obviously not ideal. It still clocks in at 1 LI but only barely so (download weight 1.3) and I want to be able to link two stacks at 1 LI and also reuse the same mesh for larger containers. By doubling the height with a loose vertice I can increase the last swap distance to more than 6 m and with two other tricks (more about them later) I can cut the triangle count down to 22 and download weight to 0.6. That's more like it! Thre triangle counts for the three other LoD models are 236, 110 and 56 (yes, I've reduced the highest model too, keeping the 24 curve resolution but eliminating all hidden tris).

I'm not sure which LoD models I captured in these zoom out pictures, because the swaps between them aren't noticeable:

It goes all the way down to a single little dot with no visible distortions or jumps between LoD models. That's how I like my 1 LI meshes

I mentioned two other tricks. This is how the lowest LoD model looks:

I removed the caps from all the cylinders and applied its texture to one not very obvious triangle in one of the sides (the one selected in the right picture). This is a very useful trick. Sometimes we don't really need all faces for all LoD models but SL still require us to keep them.

The other trick is to exted the top cylinder all the way to the bottom of the mesh, of course also extending its UV map accordingly:

The reason is that curve resolutions as low as three or four creates visible gaps between the bottom cylinders. This extension closes them.

There is no decimation algorithm that can do retopo tricks like these two and that's why I'm a bit sceptical to @animats' various proposals of replacing GLOD. I'm sure a more suitable algorithm would be a big improvement but it can also become an excuse for laziness and if you really want to optimize, you have to do it manually. Humans are still smarter than computers and for that we should be grateful.

Here's another retopo solution I tried for the lwoest LoD btw:

It reduced the triangle count to 15 and the download weight to 0.1 and on its own, it looks just as good as the 22 tri option. It creates a noticeable shift in texture alignment between low and lowest though. That wouldn't be a problem with a plain metal (or wood or whatever) texture but it won't do for something as busy as a tin can label. And yes, I could have cut it down to 13 too but there was no point since this solution wasn't useable for this mesh anyway.

Finally, here's the max size those cans can be scaled up to:

I wanted to be able to get them up to oil drum size but I may have overdone it.

Edited February 16, 2020 by ChinRey

[Wulfie Reanimator]

I've been watching a ton of crafts videos lately and I had Blender open while watching this:

It's 602 tris total, not totally cleaned up and definitely fits in 1 LI but I just wanted to show / bump.

Edited April 15, 2020 by Wulfie Reanimator