A dialogue about Vertice Counts and SL

[14:49] Gaia Clary: the vertex count shown by the importer is NOT the vertex count of the pure model.
[14:50] Gaia Clary: no, it is not borked, it is one of these unlucky terminology bendings that LL loves to do 🙂
[14:51] Gaia Clary: the vertex count has to do with the number of vertex normals needed for your mesh.
[14:51] Gaia Clary: i give you one example.
[14:51] Bondmaster: Let me guess… it counts a vertex multiple times for each face it belongs to…
[14:51] Gaia Clary: not exactly
[14:51] Gaia Clary: its more complicated.
[14:52] Gaia Clary: make and example.
[14:52] Gaia Clary: create a default sphere (with 8*8 faces)
[14:53] Gaia Clary: now when ou make an 8*8 uv sphere this has 64 quads.
[14:53] Gaia Clary: now triangulate that in blender.
[14:53] Gaia Clary: just as a show case.
[14:54] Gaia Clary: of course now you get 112 triangles
[14:54] Gaia Clary: and it was not 64 quads (i am still polluted from sculpted prims 🙂
[14:54] Gaia Clary: well.
[14:54] Gaia Clary: 112 triangles.
[14:55] Gaia Clary: now export that to collada and fire up the SL importer
[14:56] Gaia Clary: you see the number of triangles is the same
[14:56] Gaia Clary: but the number of vertices has raised from 58 in blender to 240 in SL…
[14:57] Gaia Clary: now do a trick 🙂
[14:57] Gaia Clary: go back to blender
[14:57] Gaia Clary: go to object mode
[14:57] Gaia Clary: select smooth shading on the object.
[14:57] Gaia Clary: export again and see what changed!
[14:58] Gaia Clary: now you see .. 58 vertices …
[14:58] Gaia Clary: and now you wonder what happens ?
[14:58] Gaia Clary: i am not 100% sure but i believe its like this:
[14:59] Gaia Clary: in the last import you had only face normals and not a single vertex normal.
[14:59] Gaia Clary: face normals can be calculated from the faces.
[15:00] Gaia Clary: so they need no extra information, just the triangles are enough to specify the object.
[15:00] Gaia Clary: good for vertex count.
[15:00] Gaia Clary: now back to the first example.
[15:01] Gaia Clary: here each vertex has been associated to a number of different vertex normals.
[15:01] Gaia Clary: to demonstrate this, go back to blender
[15:01] Bondmaster: So… vertex are doubled  to create a break in a continuous surface and have a sharp edge?
[15:02] Gaia Clary: bondmaster, sort of yes, in fact its even worse.
[15:03] Gaia Clary: first of all the vertex normals have to be recorded.
[15:03] Gaia Clary: then there is one vertex normal for each adjacent face
[15:03] Gaia Clary: that means. each vertex has at least 3 vertex normals.
[15:03] Gaia Clary: the vertices at the poles have even more of them.
[15:04] Gaia Clary: that means:
[15:04] Gaia Clary: he Sl importer counts:
[15:04] Gaia Clary: 58 vertices.
[15:04] Gaia Clary: plus 3 times 58 vertex normals
[15:04] Gaia Clary: plus some more for the poles.
[15:04] Gaia Clary: sums up to 240 in this case.
[15:04] Gaia Clary: and we are not finished here…
[15:05] Gaia Clary: as soon as you add a UV layout to the object, you get even more data.
[15:05] Gaia Clary: and that will also be counted as additional vertices.
[15:05] Gaia Clary: it has to do with seams.
[15:05] Kiara (kiaralynne): Wow…
[15:05] Gaia Clary: in the worst case, when you unwrap your model and mark all edges as seems…
[15:06] Kiara (kiaralynne): no wonder numbers seem odd
[15:06] Gaia Clary: let me see what happens… i never tried that 🙂
[15:06] Darien Caldwell: I’m surprised LL would consider seam data at all
[15:06] Darien Caldwell: it’s irrelevant to the model in-world
[15:06] Gaia Clary: 336 vertices now.
[15:06] Gaia Clary: no, its not irrelevant.
[15:07] Darien Caldwell: well seem so, I could just remove the seam marking off my model after unwrap, and now it’s less vertices?
[15:07] Gaia Clary: a seam actually leads to a duplication of UV information for each UV vertex that is laying on the seam.
[15:07] Darien Caldwell: marking is only used during unwrap
[15:07] Gaia Clary: yes. thats it, Darien.
[15:07] Gaia Clary: the extra information is hidden in the UV Map.
[15:08] Darien Caldwell: interesting
[15:08] Gaia Clary: after unwrap you can remove the seams but that wont help anything