Visible tiny gap between tangent edges

[Oct Oyen]

I've broken a large single mesh (a house) into a group of smaller mesh by using Blender's Separate function. The seams between the smaller meshes are tagent edges. But after imported it into SL, there is a tiny visible gaps between all tagent seams.

Is there a workaround or better way to separate the meshes in Blender?



[ChinRey]

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Oct Oyen wrote:

Is there a workaround or better way to separate the meshes in Blender?

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Yes. Blender uses 64 bit decimals for positions and dimensions while SL uses 32 bit. Just make sure the dimensions fit 32 bit decimals and you'll be fine.

No, seriously, you probably want an easier way than that.

Keep the dimensions of all the meshes at an even number of millimeters - like 9.622 m should be fine, 9,621 is risky. I can't guarantee that trick always works but it hasn't failed for me yet.

[Drongle McMahon]

"SL uses 32 bit"

Unfortunately, this isn't the case for uploaded mesh data. For the positions within each mesh, the upload data only uses 16 bits for the position on each axis. These positions are scaled by a factor depending on the size of the mesh in each domension, so that the whole 16 bit range is used for the extent of the mesh. This means the absolute accuracy of the positions depends on the size of the mesh. Because the scaling factors are variable (65536/extent), it isn't necessarily going to help aligning to mm. To be sure poistions won't be subject to rounding, you would have to make sure all your vertices fitted exactly with 1/65536 of the bounding box in each axis. I suppose you could do this if you set the bounding box to, say, 65.536m and then made all vertex positions exact in mm. With a different extent, the mm alignment would not avoid rounding errors. Also, if you have two mesh pieces with different sizes, and therefore different scaling factors, the rounding errors in reduction to 16 bits might well affect two coincident points differently. Perhaps the best advice here is to choose splitting boundaries where these errors will have the least obnoxious effect?

[Oct Oyen]

"Perhaps the best advice here is to choose splitting boundaries where these errors will have the least obnoxious effect?"

 

That would be the best solution for now. Hopefully Sansar won't have this issue. Thanks guys.

[Cyndi Sveiss]

Gaps appear when a mesh is badly built. Imagine you have a straight 3D line with 3 points on it : A-B-C. If you have a triangle having a side A-B, and another having a side A-C, then you will have a gap !   What you must do to fix that is split your second triangle into A-B and B-C.