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Author Topic: Masking and texture overspill  (Read 2997 times)

cbnewham

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Masking and texture overspill
« on: January 19, 2014, 11:24:00 PM »
I have noticed on several occassions I get overspill in the texturing, even though the dense point cloud clearly shows that the model is correct, and the points in the cloud have the correct colour. By overspill I mean where the edge of one surface is being projected on another which lies on top or underneath.

What is the solution to this? I can't mask the edge because it is part of what I am modelling. In one case I noticed it was happening because I had several photos taken at a different lens focal length (the cameras were in the correct positions in the 3D view). When I removed these cameras from the texturing it seemed to produce the correct result. Odd.

Andrew

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Re: Masking and texture overspill
« Reply #1 on: January 20, 2014, 12:17:16 PM »
This is something I have been experiencing a lot as well - texturing algorithm seems to be taking shortcuts with projection, ignoring some of occlusion. You may have a flat surface with a pole in front of it, and while dense point cloud will represent surface behind a pole perfectly (thanks to photos taken at angles), texture algorithm will often project that pole onto a wall, using the front camera instead of those at angles that dense cloud algorithm used.

Agisoft, any suggestions? Perhaps some future work is planned to improve texture projection in these circumstances?

-Andrew

Alexey Pasumansky

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Re: Masking and texture overspill
« Reply #2 on: January 20, 2014, 01:43:09 PM »
Hello cbnewham and Andrew,

Can you please post some screenshots (solid and texture view) and confirm that you are using latest build?
Best regards,
Alexey Pasumansky,
AgiSoft LLC

cbnewham

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Re: Masking and texture overspill
« Reply #3 on: January 20, 2014, 03:56:18 PM »
1.0 Build 1795

I also see it has invented some extra surfaces (left hand edge) where there is no dense cloud. I've captured the screens shots straight from each view in PS, so I'm not sure how that has happened. I generated this model yesterday and was messing around trying to remove the spill on the texture, so the extra edges may be something I've done, although all I did was masking (I didn't edit the mesh outside PS)... but the overspill has always been there (except when I remove the last few photos you can see in the thumbnails at the bottom when I generate the texture).

vfxman222

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Re: Masking and texture overspill
« Reply #4 on: January 20, 2014, 10:48:57 PM »
I've actually noticed something similar on a face capture I'm toying with. It reminds me of the "Smooth" option from 0.9, but choked tightly to the primary mesh. Here's some screen caps:

--
David Torno

cbnewham

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Re: Masking and texture overspill
« Reply #5 on: January 22, 2014, 12:13:35 PM »
I've done some more investigation.

The example I gave is not actually an example of the overspill - which I have seen on another example (I'll dig that out at some point and post it).

However, what I do notice with this (above) example is that the mesh surface generation with "interpolate" (the default) generates surfaces that just don't exist in the dense cloud. In the example shown, the mesh is being extended past the bottom of the skirt and also past the edge on the left hand side where there are no dense cloud points. These mythical surfaces then get other parts of the photographs projected on them when texturing is done. When I generate the mesh with no extrapolation or interpolation the result is correct (albeit with all the holes not filled in).

One aspect of these examples is that the photos are mostly taken from above, with very foreshortened views of the vertical sides of objects. My intention is to generate overhead views, so I'm not too interested in missing detail from the sides of objects. This all works fine except for those non-existant surfaces that are being generated.

A work-around for my case is to use height field generation. This does produce a "correct" result, but I would have thought surface generation in the normal, arbitrary, way would produce a correct result too. I don't know much about how meshes are generated from point clouds, but I find it surprising that the algorithm would construct surfaces that have no points to be constructed from!

Alexey Pasumansky

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Re: Masking and texture overspill
« Reply #6 on: January 24, 2014, 02:06:27 PM »
Hello cbnewham,

Extrapolation and Interpolation methods create some interpolated geometry to fill up holes, also some additional faces may be reconstructed next to object edges like on your sample. I can suggest to use Bounding Box so cut off unwanted area.
Best regards,
Alexey Pasumansky,
AgiSoft LLC