Half of the Polygons disappear after uploaded this mesh to SL. How to fix this?

[Yasojith]

I created a flower arch using 3d max, (as I'm not familiar with Blender). As 3d max made dae files can't upload to SL (perhaps due to it has a lot details), I export it from 3dmax as obj file then import it to Blender then make dae file using Blender then upload to SL. That is the regular way I make mesh and it workes so far.

Today when I make the flower arch, the flower and leaves made using "planes". As "planes" has one side only when uploaded to SL, I made a duplicate of that planes and flip the side and added behind textures for those. So the both sides of flowers and leaves are exactly same position. 

When I import to the Blender, I can exactly see the both sides of the flowers and leaves, even both sides are one over another at same position.

So once I uploaded the mesh into SL, I can see only one side of flowers and leaves. Pls see the attached image.

It seems like SL automatically ignore polygons, if the other polygons exactly over it.

So I can make little gap between two planes and make the flowers and leaves again, but its several hours of hard work.

I just wondering is there any easy way to fix this issue using Blender or 3dmax?

Thank you very much for any kind advices. And English is my second language so please excuse for weird writing.

Edited June 1, 2018 by Yasojith

[OptimoMaximo]

17 minutes ago, Yasojith said:

It seems like SL automatically ignore polygons, if the other polygons exactly over it.

That can happen if you put more than 8 materials, otherwise SL displays both sides when you do the procedure you described. I would make sure that the "behind" parts do have normals pointing the correct direction before you export.

[ChinRey]

50 minutes ago, Yasojith said:

It seems like SL automatically ignore polygons, if the other polygons exactly over it.

It doesn't. That can actually be a problem sometimes.

But did you sue the "Remove doubles" function after you created the flipped planes? Blender will automatically merge polys who have all vertices in common even if their normals are different and you don't necessarily notice that in Blender unless you have switched backface culling on.

[Chic Aeon]

20 minutes ago, ChinRey said:

But did you sue the "Remove doubles" function after you created the flipped planes? Blender will automatically merge polys who have all vertices in common even if their normals are different and you don't necessarily notice that in Blender unless you have switched backface culling on.

So this means you can have a "two sided plane"? I have never tried that. I always leave some distance. Interesting. Any down side?

[arton Rotaru]

2 hours ago, Yasojith said:

I just wondering is there any easy way to fix this issue using Blender or 3dmax?

Did you perhaps used the Blender preset in 3ds Max OBJ export dialog? This will check the optimize Vertex box in the exporter. If so try to uncheck Vertex under the Optimise section to keep the doubles.

3ds Max is pretty much capable to export SL compatible meshes. I use it all the time actually.

[arton Rotaru]

1 hour ago, Chic Aeon said:

So this means you can have a "two sided plane"? I have never tried that. I always leave some distance. Interesting. Any down side?

No we still don't have double sided planes in SL. Keeping a tiny gap is the most safe way to keep the auto LOD generator working correctly.

[ChinRey]

5 hours ago, Chic Aeon said:

So this means you can have a "two sided plane"? I have never tried that. I always leave some distance. Interesting. Any down side?

I don't know about the auto LOD generator Arton mentioned since I would never dream of using it. But apart from that, the only disadvantage is that selecting one of the two planes while working in Blender can be a bit cumbersome.

[OptimoMaximo]

Removing doubles in such a situation would create what is called lamina faces, which is as bad as non-manifold geometry. No wonder that 3DSMax would do an optimization during export by removing the already existing vertices. As Arton noted above, there's no actual reason for bridging your meshes through Blender, I use Maya and i export from there as well, no problem with uploading exactly like Arton does from 3dsmax.

Since i'm at it, quick definition of the two geometry monsters, lamina faces and non-manifold, so you know what to avoid in general:

Lamina faces: faces that share ALL vertices (like the overlapping surface you did with inverted normals)

Non-Manifold geometry: Mesh object that has connected geometry running through the volume of the object.

[ChinRey]

2 hours ago, OptimoMaximo said:

Removing doubles in such a situation would create what is called lamina faces, which is as bad as non-manifold geometry.

Just to clarify, I was not talking about lamina faces but collocated ones - polys with exactly the same shape, size and position in the mesh but each with their own set of vertices. Lamina faces are indeed bad for the 3D modelling software but collocated ones shouldn't cause any special problems - apart from the obvious practical challenge of selecting the right one while editing.

[OptimoMaximo]

7 minutes ago, ChinRey said:

Just to clarify, I was not talking about lamina faces but collocated ones - polys with exactly the same shape, size and position in the mesh but each with their own set of vertices. Lamina faces are indeed bad for the 3D modelling software but collocated ones shouldn't cause any special problems - apart from the obvious practical challenge of selecting the right one while editing.

Oh yes, i was talking about the optimization feature that 3dsmax does on export that Arton explained earlier, and why it would do so instead of just removing doubles while keeping the face in place. However you can easily select the geometry in such a situation by using UVShell/UV Island selection, but i'm not sure whether Blender can do that on the 3D viewport or only on the UV Map.

Edited June 2, 2018 by OptimoMaximo

[ChinRey]

2 hours ago, OptimoMaximo said:

but i'm not sure whether Blender can do that on the 3D viewport or only on the UV Map.

You can do that or similar in Blender too but it's not as easy as simply clicking on the poly you want.

[Yasojith]

20 hours ago, arton Rotaru said:

Did you perhaps used the Blender preset in 3ds Max OBJ export dialog? This will check the optimize Vertex box in the exporter. If so try to uncheck Vertex under the Optimise section to keep the doubles.

That was what exactly Happened. As you said I unchecked the "vertex check box" and uploaded again and it is visible well. 

 

6 hours ago, OptimoMaximo said:

As Arton noted above, there's no actual reason for bridging your meshes through Blender, I use Maya and i export from there as well, no problem with uploading exactly like Arton does from 3dsmax.

All the time I get an error when uploading to SL after making dae using 3d max. Perhaps I should follow this again http://wiki.secondlife.com/wiki/Mesh/Exporting_a_mesh_from_3ds_Max  I'm using 3dmax 2013, as the wiki page mentioned I would look for Autodesk FBX 2013.2 or would remove all the spaces of the contents of the mesh.

 

Here I attached the flower arch I made. It looks having less polys because it (Flowers and frame both together as one mesh) is made for 1.492 land impact aka 1 Prim. Size is 5.71833x1.98643x6.06078 meters. Any suggestions or criticisms are welcome regarding this flower arch.

Thank you very much for all your support OptimoMaximo, ChinRey, Chic Aeon and arton Rotaru. I learned new things from this discussion.

[Chic Aeon]

Certainly looks good for one land impact.  Since we don't know if you know about LODs in Second Life, be sure you test your items when viewed from a distance (preferably with LOD setting at 2 or below)  2 is the Firestorm default, 1.25 is the Linden Viewer default.  Lots of threads on this in the mesh forums. 

The other thing you might think about (and this is a personal choice of course) is that the scale of all the objects in the picture are a bit big -- for my taste and current trends anyway :D).   Your avatar seems pretty lost in the photo.  Oversized furniture and houses were the standard for many years in SL but for the last few years people have tended towards more naturally sized items.  IF you make your trellis smaller, the LODs WILL switch settings at different distances rather than how they do at this size --- so again testing is good. 

Pretty textures.  Glad you got things to work out. 

 

[OptimoMaximo]

23 hours ago, Yasojith said:

All the time I get an error when uploading to SL after making dae using 3d max. Perhaps I should follow this again http://wiki.secondlife.com/wiki/Mesh/Exporting_a_mesh_from_3ds_Max  I'm using 3dmax 2013, as the wiki page mentioned I would look for Autodesk FBX 2013.2 or would remove all the spaces of the contents of the mesh.

Best practice for Autodesk Maya is to export to fbx version 2011 and then run it through the FBXConverter 2013.3, although exporting Collada directly without the converter works as well, even if i get a slightly higher LI or Complexity value if i do so.