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.
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.
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.
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.
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.