Will someone please explain the mesh land impact calculator?

[LichtorWright]

(I'm referring to Land Impact as LI)

I don't understand the LI calculator at all!

I understand how the LI system works.. the 3 tiers. What I don't understand is the stupid calculator when you upload an object or link set.

I'm trying to make a bridge and when I'm uploading this bridge, it would seam to me, that when you upload, there would be some kind of uniform calculation for the triangles. This is NOT so.

I was having issues with the land impact when uploading it as a link set. What I'm trying to understand is, when you upload a mesh that has multiple objects. Why are the land impacts for individual parts of the link set so different. It seems it has nothing to do with the number or size of the triangles.

Below there are 2 images. both images show a separate part of the floor and the LI for that specific part.

First Part

Second Part

 

Why is the download portion of the LI for the second part SO MUCH HIGHER than the first, even though it has less triangles thus making it smaller in size? WHY?... (mumbles profanity incoherently). If someone could please explain this to me, I would appreciate it very much..

 

Thanks ahead of time :),

Lee.

[Drongle McMahon]

You say the second one (2.2 download weight) has fewer triangles. Are you sure? Does it say so in the uploader? What about the vertex counts in the uploader? That's more important ( vertex=16 bytes; triangle=6 bytes). There are various possible causes for higher vertex counts, including sharp vs smooth edges and UV seams. Do they both have UV maps? Most important of all, how are the lower LOD meshes made, and how many triangles/vertices do they have? For something this size, the lower LOD meshes will have more influence over download weight than the high LOD.

[LichtorWright]

I didn't even think about the LOD causing the issue, but that actually makes a lot of sense. Yes, I'm sure it has fewer triangles. and I don't know what the uploader has to say because I'm uploading it as a group of meshes.. which rezzes as a linkset. Either way, it's a 6 sided cube, elongated to look like a board with an array modifier.. I've simply separated it into parts after I've applied the array. 6 sides x 2 tris per side = 12 tris per cube... The first object has 12 more tris than the second object. Which also means the second object has 4 fewer vertices.

 

However, I'm pretty sure it's the LOD differences that's causing the issue, now that you've mentioned it. So, I'll accept that as the correct answer.. Thank you very much.

[Drongle McMahon]

For completeness, here is another possibility...

Vertex counts in Blender (sounds like you are using that) and in the uploader are not the same. In the uploader, every geometric vertex has to be duplicated if it appears with different combinations of normals (sharp edges) or UV coordinates (UV seams ). So in general, the vertex count in the uploader is greater than in Blender. However, that sounds like it's the same for your parts. You didn't mention UV at all. Was the original cube UV unwrapped before applying the array? After?

If there is no UV map data for an object (if it wasn't unwrapped in Blender), the uploader appears to use uninitialised memory instead, which causes effectively random UV maps. This can lead to large variations in download weight because sometimes vertices, at the same place but for different triangles, end up with the same UV coordinates (eg if the memory was full of zeroes) and sometimes they are all diffrerent. So if there's no UV mapping, that can be another source of unexpected differences in download weights (and thus in LI).

[LichtorWright]

The UVs were unwrapped after I applied the array, so all the faces wouldn't take up the same texture space. I needed individual space for shadowing. There was a UV map associated with that specific object when I tried uploading it. There was, however, another object in the link set that didn't have a UV map associated.. I don't know if that could mess with the upload calculations or not..

I'm still pretty sure it had to do with the LOD because, I uploaded that same thing several times on the beta grid and it had varied LI depending on it's place in the linkset.. If it was the root, the LI was lower, if not, higher. Like 2LI (Download) when root compared to 9LI (again Download) when not.. The only thing is, I have no idea how to make that specific mesh in the uploader root.