Second attempt scanning. Mesh density questions.

Questions, problems, comments and tips regarding the 3d scanning process.

Second attempt scanning. Mesh density questions.

Postby Datto » Mon Apr 11, 2011 5:34 pm

Hello, everyone.

I made my first attempts at scanning this weekend, and initial results are encouraging , but I do have questions. I have a screen-grab I'll attempt to upload. The bust is put together from about 6 (i think) scans, and shapefusion filled in some holes where the sculpture didn't allow the laser to scan those parts of the surface. I see that those are the parts of the mesh with the largest polys, but why is there such a variety of densities on the mesh otherwise? Is there something I can do at the scanning stage to get more consistent densities? Thanks :)
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Re: Second attempt scanning. Mesh density questions.

Postby MagWeb » Mon Apr 11, 2011 7:06 pm

Hi,

think there´s little to do in the scanning step. The only thing you can try is to get the object always at almost the same distance. But the either problem remains: There are always areas that are hard to get while others are captured several times....

The key to get a more equal density is to choose a right-balanced fusion resolution - think in your case you could minish it quite a bit: keeping details but throwing away unnecessary vertices.
Or:
reduce the high-res-fused mesh.

To get a equal density you can reduce and subdivide the mesh several times in a third party app. This soft viewtopic.php?f=8&p=16879#p16879 can do a mesh density egalization.

Gunter
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Re: Second attempt scanning. Mesh density questions.

Postby Datto » Tue Apr 12, 2011 3:02 am

Thanks, Gunter! I turned down the fusion resolution, and immediately saw improvement. I will continue to experiment.

AS far as getting the laser to scan the shadowed parts, is there any reasin I can't move the laser to below camera level to capture those hidden parts? The bust is raw plasticene clay, so it can't be laid on its top without damage. Thanks again :D
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Re: Second attempt scanning. Mesh density questions.

Postby MagWeb » Tue Apr 12, 2011 6:51 am

Hi,

maybe you could put the object on a narrow, higher stand and a use a higher corner (where the patterns are fixed with an offset to its bottom edges)? This should make it possible to put the laser below the cam.

Or:

....Don´t know if that might work with a planeless scan (for this is´nt a regular motion. Using RememberedPlanePoses might work - Anybody tried that?)
... but for a "normal" scan (or a window setup) you could try johnrpm's idea of putting the object and the corner above a horizontal mirror.
Now, sweeping the laser down onto the mirror, it reflects as if it would come from below:
Image

Gunter

EDIT:
Forgot to mention above:
To deal with different mesh densities in further virtual sculpting you could give SCULPTRIS a try:
Setting e.g the Draw brush's strength-value to zero and its detail-value (which is the mesh density value) to the wished value, brushing over the mesh its automatic tesselation (subdivision) only adds polys where the mesh owns a smaller density. (but to do that, the mesh´s size is limited (here about 500000 tris) depending on your machines muscles)
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Re: Second attempt scanning. Mesh density questions.

Postby Datto » Tue Apr 12, 2011 2:15 pm

Thanks again, Gunter. It's funny there has been a mirror on the table where I've been doing my scanning. I guess i should move it over a bit.

I've been curious about sculptris, I'll give it a try. It's still free, right?
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Re: Second attempt scanning. Mesh density questions.

Postby MagWeb » Tue Apr 12, 2011 2:58 pm

Hi again

Sculptris is still free
But since its new owner put it in some dusty drawer for a year:

:!: :!: :!: I just found Meshmixer added automatic tesselation and sculpting tools :!: :!: :!:

Download for free:
http://www.meshmixer.com/

:lol: :lol: :lol: - I found this visiting the old Sculptris forum

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Re: Second attempt scanning. Mesh density questions.

Postby Datto » Tue Apr 12, 2011 5:26 pm

Thanks again, Gunter :)
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Re: Second attempt scanning. Mesh density questions.

Postby Datto » Mon Apr 18, 2011 10:42 pm

I tried using a mirror for scanning the underside of the sculpture. Great in theory, but I got a ghosted laser line due to the two reflections, one off the silvered backing of the mirror, and one off the surface of the glass. The result was the strange striations you can see in the green portion of the mesh. Of course I was using a medicine cabinet mirror, not an optical mirror. I thought the results would be of interest.
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