ShapeFromSilhouette – part1

“Shape from Silhouette” is another reconstruction technique based on photography.
the idea is very simple . I found a nice explanation of the technique here.

thanks to Juliette’s hard work (during her oneweek school internship) I had a sequence of twenty 3K pictures with their mask to work with.The Giraffe toy has been on my desk forever and I thought it would make a good candidate for reconstruction.
3D cameras were extracted from the pictures using 3DEqualizer and lens distortion was removed using WarpDistort.

originales.gif

masks were created with XSI FxTree.

mask2.jpg

I started to experiment with PointClouds and Sops but I quickly became limited by the number of points.

pointcloud1.jpg

the interface was severely crawling over one or two millions points in the UI so I switched to i3d.

Camera Projected UVs were stored in a i3d sequence , so for each voxel a simple lookup of the mask is done and the density is set to the value of the mask. the results are accumulated frame by frame to refine the final object.

you can see the iterative process here . this little piggy guy was a gift I get while working on this project.I started initially my tests with him but he turned out to be more difficult to have nice results than the giraffe. It gave me a good taste of the limitation of the technique …
piggy.gif

back with the giraffe.Masks were blurred a little bit (to much maybe) to get more gradient in the density and to “blur” the final reconstruction.

first results with the giraffe.

tripsmall.gif

I used the isosurface node to extract a 3d mesh from the density i3d file.

isosurf1.jpg

normalessop.jpg

Correct normals were also extracted using the gradient3d vop node for clean rendering.

normalesvop.jpg

normales1.jpg

normales2.jpg

the new volume visu in houdini9

volume1.jpg

next step : Color!

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