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I have a .ply file which is 6mb in size. It has about 140000 faces. This is an output of a 3d scan. When I import it into blender and export it again as a .ply or a .obj, the file size is increasing to 60mb, even without making a single change (No modifiers, no change in scale, no change in mesh, nothing!). Can someone help me in figuring out why this is happening? Thanks

What is that blender is adding to the imported file to make it 10 times bigger in file size?

Also, i tried decimating the object to a ratio of 0.1 and still the exported file is 9mb, while the original 3D scanned file is just 6mb.

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    $\begingroup$ perhaps your 3d scanner is exporting as .ply binary (compact storage), and blender exports as .ply ascii (less compact, but human readable). en.wikipedia.org/wiki/PLY_(file_format) $\endgroup$ – zeffii Dec 27 '15 at 16:14
  • $\begingroup$ Ohh, may be. Is there a way I can check that? $\endgroup$ – Sum-Al Dec 27 '15 at 16:22
  • $\begingroup$ try look at the .ply in a text editor $\endgroup$ – zeffii Dec 27 '15 at 16:23
  • $\begingroup$ This is how it looks like (3d scan output ply): à²r˜ÓjC2—£Dà²rÂ.¶€CTœ¢D.à²rÂ.û€C ”¢D2à²r°ßsCjU£D(à²rÂüdvCÌ8£D(à²rÂð·mC"‰£Dà²rÂHœpC8t£Dà²r¤€sC $\endgroup$ – Sum-Al Dec 27 '15 at 16:26
  • $\begingroup$ yep, that's binary (not human readable) $\endgroup$ – zeffii Dec 27 '15 at 19:07
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Blender's .ply importer can handle two kinds of .ply file.

  • ascii (plain text -human readable, but large file sizes)
  • binary (data is stored in a compact way, and must be decoded before it becomes human readable)

Blender exports neither .ply or .obj as binary, so expect larger file sizes as exports.

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  • $\begingroup$ Just curious, do you know if there's a converter tool to strip a non-binary .ply down to binary? Because it seems that would address OP's concern with file size, while keeping the essential data intact. $\endgroup$ – Mentalist Dec 27 '15 at 18:47
  • $\begingroup$ Nope. I don't know of any Blender exporter for .ply or .obj that saves as binary. The question seems to really be why there's a difference in size. $\endgroup$ – zeffii Dec 27 '15 at 19:07
  • $\begingroup$ Right, but what I mean is: maybe there is a separate script or app outside of Blender that can take an ASCII .ply and reduce it to a binary .ply. Wait, actually I'll just search online... Hey! Turns out there is a way to convert them :-) I'll post an answer. $\endgroup$ – Mentalist Dec 28 '15 at 0:27
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When you export a .ply file from Blender it will be in ASCII format. However, you can then open it in MeshLab and re-export it as a binary .ply, which is much smaller.

This page lists instructions for doing this:

  1. Open the original (say binary) PLY file by using File → Import Mesh.

  2. Export this file to the (say ASCII) PLY file format by using File → Export Mesh As. Choose PLY file format in the Save dialog.

  3. MeshLab shows a dialog specific to PLY. Here depending on which (ASCII or binary) PLY format you want, choose the Binary encoding radio button. Your PLY file is converted! :-)

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