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.

6 thoughts on “The Theory of LOD – Understanding LOD in Mesh can help reduce land impact #SL

  1. Thanks so much Loki, your explanation of LOD has help me immensely, I didn’t actually know what it stood for, so thank you for that.

    I wonder if you would mind confirming for me. In the ‘source section’ of the upload window where you have the 4 levels the bottom 2 levels (low and lowest) are the areas we should change in order to get the best LOD inworld?

    Also I wanted to say thanks for your previous post regarding physics, I was wonder how I was going to tackle that one with the loft I’m building. You have a wonderfully simple way of explaining complex details, much appreciated

    • Yes the two lowest LOD levels, ‘lowest’ and ‘LOw’ can be reduced a lot when importing a big object. In opposite you might need to increase the lowest and low LOD layers when importing a really small object. Definitely practice on the beta grid to get a feel of ‘distance’ V ‘size’ V ‘LOD’ 🙂

      Another factor to consider is the debug setting ‘rendervolumeLOD’. If yur a regular SL user like me, you might have set it above the default setting of 1.2. I’ve started to import mesh while set to 1.2 as this directly effect how every newb to SL will see my imported objects.

  2. Thanks Loki, I did notice that when I reduced the size of smallish books I imported that the smaller I shrunk them, the worse they looked, so I’ll have a play around with those levels. Now I know I was also reducing those tricky little rings 🙂

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