The Theory of LOD – Understanding LOD in Mesh can help reduce land impact #SL

LOD is one of the biggest factors that determines the land impact of your Uploaded mesh Objects, yet many people who are getting into mesh do not fully understand how LOD effects land impact .

Here i will try and explain with little squiggly drawings in order to help new mesh makers reduce their land impacts and make more efficient builds. I am not a professional 3D modeller or a member of Linden Lab Research so what i say might be completely wrong, but it seems to work for me.

What is LOD?

LOD stands for LEVEL OF DETAIL. Every Mesh object has Four Levels of Detail and each level is visible depending on the distance between the object and your avatar. The best way i feel is to imagine every mesh object is surrounded by three rings, each representing a level of detail. The most detailed level at the centre, and the less detailed on the outside ring.

As you step closer to the object you step out of one ring into another, and thats when the LOD changes to a more detailed level.

The LOD Rings, the figure represents and avatar, my Logo represents a Mesh Object

As the avatar moves out into the Medium LOD ring, the Object is replaced with a less detailed one

Avatr has moved back and into the Low LOD ring. Object becomes even less detailed.

Moving out into the Lowest LOD ring causes the object to become very blocky from lack of detail

Eventually the avatar moves out of the LOD rings completely. At this distance the object simply disappears from view

 

Setting the LOD during upload.

So you have finished your object in Blender, Studio Max or that other one thats like putty. You have exported to a Collada format and are about to upload to SL. What you are presented with is a LOD generator showing you the Four levels, Lowest, Low, Medium and High(original file). With this generator you can change the amount of ‘Triangles’ and ‘Vertices’  each layer will have. To learn more about the upload settings visit my previous blog post about uploading mesh.

 

NOTE: When you upload the object to SL you are basically uploading a total of FOUR versions of the same model, each with less detail than the one before. The reason for this is because as SL viewer switches to a lower LOD the amount of power it needs to display the object reduces. The idea being that stuff further away will take up less computing power and in theory help reduce LAG and because its so far away you wont be able to see the detail loss.

Still with me? good, because here comes the bit most don’t know.

 

Size Matters

What i have found is that when you enlarge of shrink the object, the distance before LOD changes also enlarges or shrinks. Understanding this can greatly effect things such as land impact with larger objects, or disappearing detail with smaller objects.

For example if you make a Building out of mesh thats 30×30 metres in size, the LOD rings for this will be MASSIVE. In fact you would probably need to be in the next sim before it even changes to Medium LOD. Not to mention the land impact is through the roof. So you basically have two LOD’s that will never be seen because people are never far enough away for anyone to see them.

So why bother having them? in fact if you reduce the LOD for lowest and Low to 0 Triangles & vertices,  then reduce the medium LOD Triangles & vertices to half what its auto calculated, you will make your Object much more efficient and reduce land impact.

Enlarging the Mesh Object also enlarges the size of the LOD rings meaning a much further distance before the Levels of Detail change.

For smaller objects like jewellery or hats you need to boost the lower LODs because you move through the LOD rings much quicker as they are smaller.

When i first uploaded my new Mesh Hair Cut, i found that if i stepped back with the camera just a bit the hair would virtually disappear. I had to boost the amount of Triangles & Vertices  used in the Medium and Low LODs to stop my hair changing shape and disappearing.

Shrinking a mesh object will also shrink the LOD rings, and make the distance before the object switches levels of detail mush shorter

I hope this has not left you more confused than you were before. As always visit the beta grid and practice with the mesh uploading tools. With practice you can drastically reduce land impact for large builds and also improve lasting detail on very small mesh objects.

Comparing the beach Cabins #Sl #SLmesh

Nothing new to ad to my Mesh building skills other than realising that you can use previous models to help build new ones.

Part of my Meshing up Escapades island is rebuilding the Basic Beach Cabins. There are three types of Cabins available on the island to rent, Beach Cabins, Stilt Cabins and Barrel Cabins.

I decided the Beach Cabins would be the easiest to upgrade because i figured i could reuse elements from my Rock Cabin and the NewClubhouse i recently built. So really there was nothing new to learn meaning it was stress free and fun.

In Blender

In PhotoShop

In Second Life

 

Comparing the Old with the New

The best part was comparing the Cabins weights with the old Prim version. You can check the Objects weight costs by clicking ‘More Info’ in the build edit window.

Prim Count/Land Impact.

The old prim Beach Cabin was built with a REALLY low prim count of 8 because i used to live on a Homestead and prim allowance was tiny. The new mesh Beach cabin comes in at 13 Land Impact count but is far more detailed with gaps between planks, rickety roof top and supports. Creating something of similar detail in prims would come in above 13 prims.

 

Download Count.

This apparently represents how quick the object is to download. The old Prim cabin had a download count of 37, the new cabin just 13.4 and you do notice it pop up much quicker than the old Cabins when you log in. – Spiffing!

 

Physics Count.

The more complex the Physical shape of the object the higher the count, except i thought i had made the Physics shape in the new cabin a lot more complicated. The count shows old Cabin at Physics 11.7 while the new Cabin comes in at just 4. The old cabin was built using sculpt tool to create more detail with just one sculpt prim, then id set the sculpt to Phantom so the only the walls and the floor was physical. The New Mesh Cabin has more complex roof and even the supports are physical, yet it comes in less than half the physics count of the old Prim Cabin. KO!

 

Server Count.

This is supposed to be a measurement of the impact the object has on Second Life server resources. It is here where my New Mesh Cabin is actually a higher cost at 8.5 compared to the old Cabins 4.0. Which is slightly concerning since the Server count is probably most important in fighting lag? … isn’t it?  …..we’ll have to weight and see.

 

Display Count.

In the end the display count of the new Cabin came in at 5694 which is marginally less than the old prim Cabin that was 5994 and is only just below my much bigger more detailed Rock Cabin of 5879.

 

To be fair the Old Prim Cabin was really really basic to start with so getting performance gains from changing to Mesh was going to be hard to see. Where the new Mesh Cabin improves things are detail and appearance while also downloading and appearing quicker in the viewer. Hopefully the raise in server weight costs are not so great to effect things.

It’s all blinking coming together

I Have huge plans for Escapades island, HUGE, proper cutting edge SL stuff, so cutting edge that the tools needed to do it are not yet available on the main grid. My approach to all this would make Douglas Adams possibly proud in the way i just bumble along until everything connects on its own :-p

I was asked to join the Experience tools program (also known as the gaming tools) but i declined mostly because i don’t have the scripting knowledge they required for participation but also because i wouldn’t be able to keep my mouth shut about it lol. It’s not a problem, i hear snippets from various places and look forward to finally playing with the tools to see what is and what isn’t possible and how they will shape the experience i’m aiming for by end of this year.

Along with this is the Pathfinding tools which i loved playing with on the beta grid enhancing monsters and pets. Alongside the experience tools the pathfinder tools should make visiting locations a lot more exciting.

Now Linden Lab have come up with ‘Wilderness’ which i can’t visit because I’m not a premium resident (i know shocking) but i’ve never seen a benefit to being premium and the wilderness does not change that.

I don’t think wilderness is necessarily an attempt to ad value to premium anyways. The more LL get stuck in and try out content creation the better the understanding they’ll have to offer good tools for us. And if LL build areas to test out tools, performance and research how users interact then they might as well offer it to premium users as a little perk for being premium.

The Making of the New Mesh Clubhouse #SL #SLmesh

Slowly over the course of this year i shall be converting the vast majority of Builds from Prims & Sculpties to Mesh. The reduction in performance costs on the island should reduce as the more stuff is converted to Mesh.

By  far the biggest Mesh project i have done to date has been the rebuilding of the Goonies Club house and Loki Shop.

The Club house was first built in 2006 and has been upgraded twice before this new Mesh Version. It may no longer look anything like it did back in 2006 but I’m hoping people who were around back then will get the same sense.

So first thing i did was sketch out what i might want to do. Mesh gives a sense of freedom you don’t get with prims. I would sketch out the cubes of prims that could make up the building then realise that I’m free to do more crazy ideas such as hugging tree roots and rooftops that partially fall down..

A very quick scribble to get down the basic ideas

 Moving into Blender

Again the most daunting part ids the start, as this you have to work out sizes etc. Im not very good with numbers so working out accuracy of scale is not one of my skills.

In Blender i find that creating a build with multiple parts can result in lower land impact. It also makes it easier to work on parts of the build using the Blender Layers system.

One issue that gave me head aches was ‘Normals’ facing wrong direction. This causes object to look inside out. Blender suggests ‘flipping’ or ‘re-calculate’ normal outside, but if your object has a cut edge then it can’t figure out which side in inside or outside. Took me AGES to fix and i ended up simply rebuilding fences and steps to get it all right.

Originally started as a two floor shop, but cut the second floor back to allow a platform

Adding the giant tree and rickety steps, i love rickety steps XD

 

Final model rendered using Blender Cycles renderer

 

 

An important part of making mesh people tend not to know.

It can soon become quite easy to model a 3D object in blender once you get used to its basics. Then it’s on to texturing the object right? WRONG!

Between making a model and texturing is a really important category called ‘UV Mapping’. Think of it as putting a special coating on the object in order for the texture paint to stick to it.

UV mapping is important. It defines how your texture will be placed on the object and when fully understood you can create an object that uses one texture across multiple areas saving rendering performance.

During this project i was forced to fully work out and understand how UVmapping works, how to map them and how to create and use ‘materials’ in order to apply multiple textures to one object. UV mapping the Club house took almost as long as texturing.

This shows in Photoshop the list of UV maps i created to allow me to add textures to the model

 

Texturing.

Finally my favourite bit. If you master UV mapping, then texturing becomes even more easy and fun.

I do four stages when Texturing.

1. Base texture. This is basically just adding the desired texture for wood or or metal ore sand. Everything will look pretty much like they would if you slapped a texture on an SL prim.

2. Highlights.  I work out where the edges of objects will be and create a light line to help define the edges. This gives a sort of cartoon effect which i like.

3.Shadows. I use photoshop to texture right onto the 3D model. i Mark out where shadows should be and add them to the textures. I consider which direction a light source is coming from and make back facing dextures darker than the from facing. Shadows ad a lot more realism for those who can’t handle having SL Viewer Shadows switched on.

4. Details. Once highlights and shadows have been added to lift the build from being a flat shaded object you can then take a look and see what else you can add. Little details can be fun and can add to the experience of exploring the build. I decided to add moss on the tree roots and plan to add some more details in future such as posters, secret messages, barnacles. Sometimes you have to wait until you have it all razzed in world before you can see whats possible.

 

Building up textures is like building a puzzle. Everything looks better in photoshop as it uses a different renderer to SL

 

An example of how highlighting around the planks and shadowing on the roof can make objects stand out more

 

Uploading & Placing inworld.

So I’ve modelled the new Clubhouse, UV mapped & Textured it. The next part is to upload it and rez in world. The original clubhouse

was about 117 Land impact and i knew i had gone way over that since the new clubhouse has an extra floor, a giant tree, proper railings, rope bridge, giant anchor and is wider.

Initial upload tests on the beta grid Aditi suggested i was looking at around 260 land impact, way over the original. Comparing the two is somewhat impossible though, since they are both very different builds. The Cabin i built a few weeks ago was pretty much identical in size and shape and so a comparison could be made.

 

The LOD effect

Because the size of the new Club house was so huge, LOD (Level Of Detail) responds differently. I have yet to fully work this out but from what i can understand, the distance from a large object is longer before the LOD changes to a lower LOD. If you have a small object then the distance before the LOD changes is far shorter.

With this in mind when you upload your mesh, you can set LOD detail a lot lower for the Lowest & Low LOD because people will have to be on the other side of the island for those two lowest LOD’s to be seen. Reducing the detail on LOD layers can greatly reduce the land Impact.

Considering also where your build is situated can also allow for lower LOD. If you have a big build inside a cave, you can set the lower LOD’s really low because no one will see it until they go in the gave and are right up close to it.

I hope this makse sense to those who know what LOD is 🙂

 

The New Clubhouse has better LOD degradation than my old Sculpty Beach Cabins

The Physics

I know a lot of people painstakingly build the physics shape in blender to import and use with the Mesh. I’m lazy and can’t be arced. I tried making Physics shape once and got really poor response. What i know tend to do is build the physics shape using old fashions prims. I clear them of any texture and set them to 100% transparency. I have one major prim set as the floor and link the entire build to that physical prim. Then i turn the mesh build to have a physics setting of ‘none’. Finally i use prims to create all the floors and walk ways.

I find this is a much easier and flexible way to create the physics for mesh builds and also it hardly adds to Land Impact.

 

Result.

Im pleased with it,. It came out pretty much as i wanted. It might be a few more land Impact than perhaps necessary but it was a huge project and the smaller projects coming up should seem a lot easier 🙂 The style of modelling and texturing seems to almost be a signature style showing through which is interesting. Will my style been recognised in future?

With the Mesh Clubhouse complete I’m already eyeing up the Basic Beach Cabins and also the lighthouse which is as old as the clubhouse.