More magical linden math...

[Failed Inventor]

So today I imported a new model... a simple knife with roughly 4k triangles... with manually made lods was 4 prims. however the same knife divided up into 3 prims even with having more polygons/triangles was equiv to only 3 prims

so how does more polygons and more prims... equal less strain and cost, verses a 1 prim slightly lower model, with nearly the same exact  structure and polycount?

 

Also I am having trouble with manual LOD's... when mesh displays anything lower than highest lvl of LOD it breaks the texture. How do I do a single texture which works with all lvls of manually made and optimized LOD?

[Gaia Clary]

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Failed Inventor wrote:

so how does more polygons and more prims... equal less strain and cost, verses a 1 prim slightly lower model, with nearly the same exact  structure and polycount?

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Getting lower Prim Equivalents when you create your mesh with multiple parts is expected behaviour. As far as i understand the main reason is that smaller Objects show their lower LOD's earlier and thus they help to reduce the bandwidth. This is one of the major issues which raise when you try to make big objects (buildings). The only way to keep the Prim Equivalent small is by cutting large pieces into smaller elements.

Indeed my own experiments show that for small objects you get a large discount when you link them into one Linkset. But for larger Objects for some reason linking them increases the Prim Equivalent instead of reducing it. And i hope this is a bug.

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Failed Inventor wrote:

Also I am having trouble with manual LOD's... when mesh displays anything lower than highest lvl of LOD it breaks the texture. How do I do a single texture which works with all lvls of manually made and optimized LOD?

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Two easy ways to get reasonable LOD meshes which preserve the UV-Map:

by construction:

1. You start with the LOW level of detail mesh and model your base object. UV-Unwrap the model now.
2. You subdivide your mesh once to create the MEDIUM level of detail mesh. With Blender-2.4 you can use Multires or subsurf. With Blender-2.5 you can use Subsurf or a combination of Multires plus Subsurf (i am currently working on a tutorial for that) Similar tools should be available for other 3D tools. Subdivision should NOT change the UV-layout, so this ensures that you can use the same texture for both models.
3. You subdivide again to get the HIGH level of detail. Of course you can reshape your model and make use of the extra vertices. Just take care to not change the overall shape, otherwise you can see LOD jumping.
4. Use a retopo tool for creating the LOWEST level of detail. In Blender you can try to remove edge loops fro example, or use the decimate modifier (blender 2.5) or the poly reducer (Blender-2.4). Or simply use the generated LOD from the SL Importer.

By dedcuction:

1. You start with the HIGH level of detail model, do all your work there and create the UV map.
2. Now remove edge loops by hand, or use a retopo tool or poly reducer (as described above) for the other LOD meshes.

In the next few days i hope to release Part 2 of the "Kettle Quest series". There i briefly show the process workflow.

[Poenald Palen]

A large object would change LOD at a distance while an av was flying above and it rotates closer to him, do to the larger extension up and down around it's center?

Unlinked objects can each turn and show their other sides, that might be occluded IF they where linked in a way that they where butted...I mean, they MIGHT do this in typical builds people make. So they see them as possibly moving and ucclusion benifits are not the same?

Size might be linked to LOD and rotation is the sort of gist of what I am saying. But, I dont' know! Hense the ? all over this post (which I sometimes foget to put in)

[Drongle McMahon]

"A large object would change LOD at a distance while an av was flying above and it rotates closer to him, do to the larger extension up and down around it's center?"

The size measure used to determine the LOS distances is the "radius" of the object. This is the distance from the center of the bounding box to a corner (technically, the radius of the circumscribed shpere of the bounding box.) This does not change with changes in the angle of view. Therefore the LOD switch distances don't change either. So a telegraph pole will be the same LOD at a perticular distance from its center whether you are looking at it from the side or from above.

There is an interesting consequence of this with sculpties, which can be made to fill only a small proportion of thier bounding box. So if you make you sculpty chair 1x1x1 m, but in a bounding box that is 4x4x4 m, it will switch LOD four times further away than the same chair in a 1x1x1 bounding box. The trade-off is that you only have 64 vertex positions in each dimension instead of 255. You could do the same thing with mesh, using an invisible flap to extend the bounding box, but it would cause a big increase in cost .... unless it's an attachment!