Land impact? Are meshes just hoax with no use?

[Drongle McMahon]

"What causes the Land Impact to change when setting the object settings from "convexhull" to "prim"?"

It's all explained here. Dowlnload (LOD meshes), physics (physics mesh) an server weights are calculated and then the highest of the three is used as the LI. The "Convex hull" setting causes the object to use the default convex hull of the whole object to be used as the physics shape. When it's set to "Prim", it uses the physics shape specified at upload time. This can be either triangles (no "Analyze"), or a collection of several convex hulls ("Analyze"). Either of these can have a higher physics weight than the default hull, and if it is also higher than the download and server weights, the result will be an increase in LI.

Triangle based shapes have higher weights as they have more smaller triangles, so their weights increase as the object gets smaller. Convex hull weights, default or v"Analyze", do not vary with size, but can still be high when the pjhysics mesh has rough or rounded outside surfaces. There should be very few cases where the physics weight needs to be higher than the download weight. If it is, you can nearly always get adequate collision behaviour with a simpler physics mesh.

[Drongle McMahon]

"Am I able to do the same from mesh, with same or almost same LI, with same metric size?"

As long as you just want to look at them, sculpties will have lower LI in this case. What's more, they won't put any more strain on the gpu than the same tringles in a mesh. As they are too big to switch LOD, the sculpty LOD problems don't apply. This is one of the cases where sculpties are better.

However, as soon as you need an accurate walkable surface and/or correct collision behaviour, you can usually do better with a mesh with a triangle-based physics shape.

[Kwakkelde Kwak]

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Masami Kuramoto wrote:

 

I can see that factor right there in the OP's screenshot. Please explain why that mesh build with 8900 triangles deserves to be 32 times more expensive than a multi-prim build of identical size and triangle count. This is so obviously wrong, I don't even know what there is to argue about.

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Oh there's no denying the calculation system for the sculpts is all messed up, but all I am trying to get across is even WITH these disadvantages for mesh objects, you can still make a better build for less landimpact. That is unless you really absolutely positively need ALL the geometry used in the sculpts for ALL the LoD models. I have a very hard time believing that's the case with the gazebo, or for 99.9% of other sculpt builds for that matter.

[Kwakkelde Kwak]

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Drongle McMahon wrote:

"Am I able to do the same from mesh, with same or almost same LI, with same metric size?

"

As long as you just want to look at them, sculpties will have lower LI in this case. What's more, they won't put any more strain on the gpu than the same tringles in a mesh. As they are too big to switch LOD, the sculpty LOD problems don't apply. This is one of the cases where sculpties are better.

However, as soon as you need an accurate walkable surface and/or correct collision behaviour, you can usually do better with a mesh with a triangle-based physics shape.

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I even have to disagree with you Drongle:)

Depending on the shape even very big meshes can have a lower LI than sculpties. The bigger they get, the less oftenit will happen though I suspect. And the 64+ sculpts ofcourse do not have a mesh counterpart at all, not out of one piece anyway. So in full sim landscaping sculpts will be more forgiving without a doubt.

Now if only we could get the sculpt use reduced to these kind of objects:)

 

[Kwakkelde Kwak]

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Yan Hoxley wrote:

Ive seen your reference'bout it, but everyone could say that... Post some landmark or give us picture + LI of your large model you talking about... I want to see that

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It's a work in progress and progress is slow as it's a free build from my side and I have little time as it is. If you really really want to see it because you really really do not believe me, contact me inworld and I might do some touchups and drop you a landmark.

Going by your next post I figure you are willing to take my word for it though:)

EDIT..I see "your next post" was by Dilbert, anyway he got it figured out and I'm sure you will aswell, I do seriously not understand why you think I am making this up.

[Dilbert Dilweg]

I see now. I was hitting anaylize when I already had my physics shape specified..

Impressive. I got my pergola down to 17 land impact. Built with 14 parts. There is no way I could have made the 6 pillars with 17 prims in world. Thanks for the help

 

 

[Drongle McMahon]

"Depending on the shape even very big meshes can have a lower LI than sculpties"

Well, yes, but only if the mesh is simpler than the sculpty, but I am comparing a 64x64x64 mesh with exactly the same triangles as the sculpty. For landscaping, sculpties will typically be used without any wated vertices. Then they are no more burdensome on the gpu than the mesh with the same vertices, less data to download, and much lower LI. The big difference is that the mesh can have an accurately walkable surface, using a triangle-based physics shapes (as long as all the triangles are big).

[Kwakkelde Kwak]

When all LoD models are the same for sculpt and mesh, the sculpt will have a lower landimpact, true. That's not really fair, I agree. In fact I think we agreed on that months ago.

The thing is, those circumstances are not very likely to occur. Big boulders, blobs and other rounded objects aren't exactly the building stones of our Second Life. Buildings, furniture and even clothing can be built far more efficiently with mesh than with sculpties or prims, to the extent where even with the "LI penalty" the mesh can have not only better looks but also a lower LI.

So I don't have a big problem with the "bonus" for older building tools. I do have a small problem with how LoD works. The way it is now, one object at different sizes needs different LoD models to make it as low in landimpact as possible at those different sizes, unfortunately the LoD models are set on upload. I really don't see a solution for this, let alone a simple one.

[Masami Kuramoto]

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Kwakkelde Kwak wrote:

Big boulders, blobs and other rounded objects aren't exactly the building stones of our Second Life.

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I think you are confusing cause and effect here.

It should be possible, at least for region owners, to use a large 65536m² mesh instead of the default height-mapped land plane. This way we could have regions with fairly realistic terrain, nicely textured cliffs, and proper caves and tunnels. It should be possible to use a shared 2048x2048 texture atlas instead multiple small textures, because this would considerably reduce the number of expensive draw calls.

But then of course, it should be possible to use normal, specular and lightmaps to reduce geometry and (baked) texture sizes. Is anyone working on that yet?

[Kwakkelde Kwak]

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Masami Kuramoto wrote:

 

I think you are confusing cause and effect here.

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I am not, I am not questioning the fact the rules aren't fair, but that discussion is ancient history for me to be honest and certainly not something to discuss on these forums, since no Linden will take notice.

What I am doing, or at least trying to, is explaining how the freedom of mesh will allow lower landimpact for the majority of content and thereby answering the question the OP asked. I am sure that gazebo can have less prims and better LoD bahaviour than the sculpted version.

The waterfalls are a different story, but after playing around a bit I am sure that can be built in mesh with a landimpact of 20. This is all because of the big bloblike thing, all the other parts, including the particle scripts, texture anim scripts, offshore object and plants will be lower in mesh. Even the water can be made with a landimpact of 1 (or 1.1 really, I used a 8x4 plane for the water, using 45 verts and 64 tris on LoD high, reduced the tris to 32 on LoD med and scrapped the lower LoDs altogether).

I built the stone wall out of a bottomless 2x6x16 box, allowing quite a nice shape, on LoD med I used the auto-LoD, just to have a realistic number for it, it will take quite some distance for the shape to deform. This results in a LI of 11.

Offshore object is free, as it can be a single triangle, same for the particle emitters.

Trees are 1 prim per pair the way I made them earlier, with 6 double sides planes on all LoDs, you could even scrap the lowest LoD and get even better results.

The two rocks on the bottom of the waterfalls have a LI of 1 (1.2), using a 2x2x6 box for the base, with 94 verts, LoD med and low at 32 verts and again no LoD lowest.

So 11 (wall) + 2x1.1 (water) + 2x1.2 (rocks) +2x1 (plants) + 3x0 (particles and offshore) = 17.6 for LI,

not as good as the sculpted version, but that wasn't to be expected. The upside of the mesh version of such waterfalls is they won't affect your performance like the sculpties will. I can't judge on this particular set, but I have seen these things crippling my fps by a factor 3, making it nearly impossible to move around. I'm not 100% sure if that was due to th particle emitters or the animated sculpties to be honest, but I do know you can build something like in the picture for less than 1000 tris easily. That's less than half a sculpty.

So again, only for big objects with lots of geometry sculpties seem to be lower in landimpact.

[Masami Kuramoto]

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Kwakkelde Kwak wrote:

I am not questioning the fact the rules aren't fair, but that discussion is ancient history for me to be honest and certainly not something to discuss on these forums, since no Linden will take notice.

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If it's not worth discussing, why are you doing it anyway? Why not just face the facts: SL looks like ancient history, and the OP just figured out why.

[Monti Messmer]

Hello, i think at the end this discussion shows that advertising mesh as the new wonderful way to build in SL has failed.

While some pro´s will be able to do amazing things strangled optimized hit bumped whatever.... the majority either has mesh with higher LI or stuck with old prims for building.

There where always people able to build low-prim but everyone could start optimize their buildings with improve skills.

The steps you need to do for mesh and the knowledge needed for - external software, high low lods .... - will be about impossible to learn for, imo, the majority of fun builders or hobby merchants.

Don´t get me wrong i like mesh but my RL work don´t give me hours of time to learn and then hours to build, and you have to agree building a "perfect" mesh takes alot more time than build with normal prims (even they look worse and have a bigger LI)

Monti

[Kwakkelde Kwak]

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Masami Kuramoto wrote:

If it's not worth discussing, why are you doing it anyway? Why not just face the facts: SL looks like ancient history, and the OP just figured out why.

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I am not discussing it, you keep bringing it up.

The only thing the OP figured out is he still has some things to learn between his 3d skills and the implementation of them in SL. Nothing more, nothing less.

Making sculpts more expensive in LI won't improve the looks of SL, lowering the LI of mesh will bring us to a point where we can look at nice things but aren't able to move around between them. The reason why SL doesn't look that good is partly because of the streaming it has to do, lowering the possibilities and mainly because anyone who wants to, can build anything they like, however they like. That is a great concept, but comes at a cost.

The alternative would be all professional built content, only available in some store. If that's what you want, I think the sims or blue mars or whatever lame platform is the place for you.

The question was: "Are meshes just a hoax with no use?"

The answer is a loud and clear "No"

[Dilbert Dilweg]

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Kwakkelde Kwak wrote:

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The question was: "Are meshes just a hoax with no use?"

The answer is a loud and clear "No"

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I have to agree that they are useful now. I was struggling big time on how to make the mesh lower on land impact. I was really lost  so of course I got majorly discouraged. Once i figured it out I am really amazed at what I can make and keep them low land impcat. I am making very intricate pillars/collumns now and making them 1LI.

Very excitihng to me because now I can see I can really get into some detail and keep it low land impact. 

 

[Kwakkelde Kwak]

I'm happy to hear that

Now if everyone could try and figure it out with the offered help, instead of screaming mesh is worthless without accepting the fact there's a solution in just about all cases. Even more so, when some people are told there's a solution or when they are asked for more information, they act deaf, dumb and blind (and stubborn). That's very discouraging for people who are only trying to help.

[Dilbert Dilweg]

Hehe I can fully understand where you are coming from.  I really appreciate you all who come in here and take the time to help us no matter how noobish or stubborn we can be lol. You, Drongle, Gaia,  Ashasekayi, do an awesome job thanks

[Luc Starsider]

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Dilbert Dilweg wrote:

Hehe I can fully understand where you are coming from. 

I really appreciate you all who come in here and take the time to help us no matter how noobish or stubborn we can be lol. You, Drongle, Gaia,  Ashasekayi, do an awesome job thanks

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If you don't mind, Dil, I'll join you in this. Absolutely awsome! I learn, improve my skills and get better at creating mesh every time because of you guys!

- Luc -

[Masami Kuramoto]

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Kwakkelde Kwak wrote:

The question was: "Are meshes just a hoax with no use?"

The answer is a loud and clear "No"

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The answer is an ambiguous: "It depends on the size."

For large builds, meshes are just a hoax with no use.*

 

*) except in OpenSim.

[Kwakkelde Kwak]

Let me be a smartass and say your answer is the answer to this question:

"Is mesh always preferred over sculpties in every possible way?"

Even if you answer that question your answer isn't correct, as I showed ealier. It is only true if you use a good part or all the geometry in your sculpt AND if you do not care a single bit about being able to move around in your sim. If the LI rises by 50% or even 100% but the geometry and therefor graphical load drops by 90%, I see justification for using meshes.

That however was certainly not the question asked by the OP and therefor not the question I was answering.

 

[Masami Kuramoto]

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Kwakkelde Kwak wrote:

Let me be a smartass and say your answer is the answer to this question:

"Is mesh always preferred over sculpties in every possible way?"

That however was certainly not the question asked by the OP and therefor not the question I was answering.

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The OP provided evidence: a particular build that is 32 times more expensive as a mesh, despite identical triangle counts.

You did not debunk the OP's observation. Instead, you started talking about something else.

The OP basically figured out that mesh sucks when used for "X".

And you said he is wrong, because mesh works fine for "Y".

Bottom line? Mesh sucks for "X". The OP is right. Drongle agreed. Why are you still arguing? The numbers are right there in your face.

[Fluffy Sharkfin]

If you're finding that larger mesh objects are too heavily penalized under the new land impact system, have you considered using mesh to make smaller building components instead, then using those to build larger structures?

I recently made some mesh building components and found that the amount of detail that can be achieved using mesh goes far beyond anything possible with sculpted prims, and with significantly lower land impact.

Here are a couple of example images of build components with corresponding land impact values shown.

(single girder 1060 tris, 0.5 LI)

 

As you can see from the image above the LI stays below 1 per linked mesh object, based purely on polygon for polygon (each girder being 1060 tris and the connector in the center having 2182 tris, which makes a total of 8542 tris for 4 LI) mesh wins out over sculpted prims (4 sculpted prims @2048 tris per prim =   8192 tris).

Here are a few more example images of other build components.

 

When you also take into consideration the fact that most of the components have multiple materials to allow selective application of effects like tint, shiny, glow, transparency and texture animation, and UV mapping designed to accomodate the use of multiple seamless textures with varying repeats and offsets from each other all on a single mesh (not to mention that all 28 build components use only 6 shared textures), it becomes clear that mesh gives you the ability to create things far beyond the scope that sculpted prims can offer.

As for giant sim sized builds, back when we had a 10 meter limit on prim size, it was common to take several of these small blocks and link them together to make larger structures.  So if there's an apparent limit on the efficiency of mesh based on its size, perhaps you should try taking lots of small mesh objects and linking them together to build bigger things, like this...

If you'd rather take a look at it in person feel free, the build is currently located on my homestead sim.  I'm currently taking a break from adding to it, not because I ran into problems with LI (I've only used around 60% so far) but because the amount of geometry being displayed per frame is getting to the point where older hardware may seriously suffer if the user has their graphics turned up too high, and I'd like to keep the build efficient performance-wise as well as land impact friendly.

So, to answer your question, no meshes really aren't "just a hoax with no use", you simply need to experiment a little more and find the optimal way to use them.

[Kwakkelde Kwak]

Sigh...

WHY would someone use mesh if it behaved exactly the same as a sculpt? There would be no point, would there?

Mesh has advantages over sculpties and the other way around. Avoiding some and making good use of some others will allow people to make an object that looks the same or better for a lower landimpact and a fraction of the rendering load on your hardware. This is not the case for ALL objects, but it is certainly the case for that gazebo and for the vast majority of SL content. Building a mesh like it is a sculpty, then uploading it with the default settings will NOT give you the best results to say the least.

The OP built "X" using method "1". Nowhere did I or anyone else say "Build Y", I said "Build X using method 2". Drongle agreeing or not doesn't change my opinion, but for what it's worth, he aswell said "Build X using method 2". Build flat planes for the lower LoDs, it will not at all be noticable inworld. If the gazebo was 9k verts and the OP used the auto-LoD without changes, LoD med should be something like 4.5k, low 2.3k and lowest 1.1k. you can replace the auto-LoD for med and low with planes, you can scrap LoD lowest completely. It would cost around 50 triangles for double sided ones and 25 for single sided ones. "Well boohoo, now it is nothing like a sculpt anymore". Erm, yes exactly.

I am wondering what purpose you think these forums have Masami. I personally think it's a good place for people to ask questions if they do not understand things, can't figure things out, have problems with certain things or procedures. People can then respond with a possible solution plus some extra information. That is what I and a lot of other people try to do here and fortunately it's appreciated by at least some people.

Comments like "show me, I don't believe you" or "you can say that, but anyone can" do not encourage me to explain in more detail. This is not a "Kwak Egotrip". I try to help, people can take it or leave it. If people can't reproduce what i am saying after some trying of their own, I am always willing to help them further, but I am not going to do other peoples work. If you expect me to do that, you should hire me and I can consider it.

[Drongle McMahon]

"Bottom line? Mesh sucks for "X". The OP is right. Drongle agreed"

The scope of that agreement was rather limited. Here, X is rather a small specialised subset of things you can build with mesh - big rugged lanscape that you don't want to walk on (it also applies to some other large rounded things)*. The OPs question was whether meshes are "just a hoax with no use". To which the answer remains a resounding "No" because of the many other things, large and small, for which mesh is better and provides lower LI.

*and it isn't because mesh sucks, it's because sculpties are given unfair advantage.

[Coby Foden]

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Fluffy Sharkfin wrote:

If you'd rather take a look at it in person feel free, the build is currently located on

my homestead sim

.

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I went to have a look.  The whole thing rezzed almost instantly.  Amazing and impressive showcase of effective mesh build!

[Alisha Matova]

Interesting thread, with some good examples. =)

I only have a few words to add: Low Poly Modeling. Google it for your modeler, it is the magic key to low LI stuffs. (along with all the lod and other tricks mentioned here)