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Upload window showing more vertices? (3ds max)


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I never noticed this before until today. My friend gave me a .dae file exported from blender to optimize for him, I managed to get it from 5454 polys to 3774 using 3ds max 2011. but it costs more to upload.

 

Notice the vertex counts...

 

Blender dae:

Blender dae file

 

3DS with 2011.3.1 dae exporter:

3ds_dae.png

You can see the vertex count is completely wrong, and the generated LOD's are wrong too. It makes the prim count and upload cost go up A LOT. this 3000 poly one costs more to upload than the old 5000 poly one

 

I tried to upload some of my old meshes and noticed they are also showing too mny vertices..

 

the sl uploader says a simple cube has 24 vertexes, when 3ds says 8:

3ds_cube_dae.png

 

the meshes look fine in sl, and all the material ids and smoothing groups import fine. its just the prim cost is a lot more than it should be.

 

I have tried sl v3, second life development viewer, phoenix and firestorm, they all do the same.

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This is expected behaviour. All vertices on the edge of a smoothing group or on a UV seam are counted for every "surface".

So a box is not a box, but due to its smoothing groups (hard edges) it is really 6 square planes. 6x4 = 24 vertices.

Edit..talking about planes... you could use a plane for the lower LoDs with a picture on it instead of reduced geometry and see a dramatic drop in both landimpact and render weight. It will look better aswell I suspect.

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Jarmade Spires wrote:

the blender dae has smoothing groups too. and its vertex count is normal? I simply tried to import the .dae into 3ds and export it back out as .dae, it shows 11k vertices with no changes.

 

Well what I said should be the case, it's what I hear and see all over. Maybe the UV maps were changed between blender and 3ds, or the smoothing groups were ignored. Or there are disconnected faces.

What I am curious about though is why the 3ds model has more verts with LESS faces.

Make sure all the vertices are welded together and check your smoothing groups. I would be very surprised if you could get a box from blender to upload for 8 vertices.

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hmm i just noticed the .dae file my friend was giving me is 1.4.1, and its not importing to 3ds max properly (it lost its smoothing groups) In blender it shows as all smoothed. and also i did do a quick default unwrap on it.. so taht probably added more vertices too!

 

I think i understand now. thanks a lot!!

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the smoothing groups will have a far bigger impact, since all your triangles now have 3 verts where the ratio of triangle/vert is usually 2:1, not 1:2 (something like this anyway, depending on the shape) With no smoothing groups, the UV can't have any impact, it's as bad as it can get right now...  Also try that imposter/billboard thing and get the triangle count under 10 in your lower LoDs..now that is optimizing and will let the LI drop tremendously. Just guessing, but I think you should be able to get the LI under 5, depending on the size.

Oh and yw ofcourse!

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Jarmade Spires wrote:

Thats so strange! I set all as smoothing group 1, and it shows normal vertices. Set it with no smoothing at all. and it shows 11k vertex.

 

So.. smooth stuff costs less to render? (less prims at least) O_______O

Yes that's what I said, if you have no smoothing groups, the object is treated as seperate faces. It has got to do with the normals. a smoothed vertice has one normal, so SL can calculate the lighting/reflection between all verts making up a face. If you have a hard edge there are more normals, one for each smoothing group. i understand your surprise..better looks cost less? welcome to mesh! :) This is often the case.

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To expand a little; the upload/download data is stored as a list of triangles and a list of vertices. Each triangle has three indexes that point at the three vertices at its corners. Each vertex has position (3 numbers), normal direction (3 numbers) and UV map cooprdinates (2 numbers). If the vertex is "smooth", then all the triangles using it point to the same entry in the vertex list. B ut if it is "sharp", then the normal direction may be different for each triangle and there have to be as many entries in the vertex list as there are different normals.

Similarly, if the same vertex appears at multiple places on the UV map, because it is on one opr more UV seams, then it has to have multiple entries in the vertex list. The vertex count displayed in the uploader is the number of entries in the vertex list, and is generally more than the number of unique vertex positions for these reasons. On the other hand, most 3D programs give a vertex count that ia just the number of unique positions. Sp does the Collada file because it uses a completely different indexing structure.

To keep the LI down (if it is limited by download weight), you should only have sharp edges where they are needed, and you should have as few UV seaqms/islands as is cinsistent with good texturing. Also bear in mind that if a UV seam lies along a sharp edge it does not incur any further extra entries in the vertex list because the vertex is already duplicated.

When you optimise a mesh by removing adge loops etc., it is important to weld any newly separated UV islands back together to avoid vertex entry duplication that is otherwise caused (UV fragmentation). The extent to which this is necessary may depend on which program you are using, as some operations may maintain a joined up UV map for you. Blender is very bad in this respect. I don't know about other programs.

If a mesh has multiple materials, each material has its own triangle and vertex lists. So vertices that lie along the border between materials also have to be duplicated. Materials applied to many non-contiguous faces will therefore also increase the download weight. Of course materials will often each have their own UV maps. In that case there is no extra duplication because the UV seams have aleady duplicated the separated vertices.

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I don't understand it fully, but I don't think Collada includes the concept of smoothing groups. It has separate geometry tables, of positions, normals and UV coordinates. Then, for each meterial, it has a triangle list (or polygon list). Each triangle has nine indexes, three corners, each of which has an index into each of the three geometry tables. If the three normals are the same, the triangle will be (part of) a flat facet. If it is part of a smoothed surface, the normals will be the same for all the triangles meeting at each corner.

It is possible for the triangles meeting at a point to have the same values for all three tables at the shared point. In that case, an import function could use that information to imply that the triangles belong to the same smoothing group, although I doubt that most importers would. However some exporters (at least Blender 2.49) don't reuse normal or UV table entries this way. They replicate these values for each ocurrence, leading to tables with many redundant identical entries. In these cases, an importer would have to explicitly compare all these values to decide things like smoothing groups. In fact the Blender 2.49 importer doesn't seem to use the normal information at all. If you export a smoothed sphere (which SL recognises as smooth), then import it, you get a faceted sphere with all sharp edges!

 

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well thanks a lot, you two. Really helped me understand things a lot more.

 

The other day on my mesh avatar, i did a quick default unwrap to set all the faces (quads) on my mesh to fit the uv space, so that i could apply a bordered texture and see the wireframe.. now that really explains why the upload cost went up tonnes! hehe

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