## Friday, May 6, 2016

### Multi View Stereo - Whittemore mausoleum

Let's see the effect of the min separation angle (low-confidence 3D points) on the 3D reconstruction produced by Multi View Stereo 10 (MVS10). If the separation angle of a 3D point is too low, it is kind of assumed that its position is not too accurate and it should probably not be in the dense 3D reconstruction.

Set of five 1080x1920 views/images for which we want MVS10 to build a dense 3D reconstruction.

Let's start with min separation angle (low-confidence 3D points) = 0.5. Incidentally, we are using min image point number (low-confidence 3D points) = 3 and max reprojection error (low-confidence image points) = 2. Those are fixed.

Dense 3D reconstruction using min separation angle (low-confidence 3D points) = 0.5.

MVS10 outputs:
Number of 3D points = 1,042,740
Number of 3D points removed because behind ref camera = 23,384
Number of 3D points removed because separation angle too low = 42,701
Number of 3D points removed because too few image points = 663,332
Number of 3D points = 313,323

Let's move on with min separation angle (low-confidence 3D points) = 1.5 and see what happens to the 3D reconstruction.

Dense 3D reconstruction using min separation angle (low-confidence 3D points) = 1.5.

MVS10 outputs:
Number of 3D points = 1,042,740
Number of 3D points removed because behind ref camera = 23,384
Number of 3D points removed because separation angle too low = 261,161
Number of 3D points removed because too few image points = 446,460
Number of 3D points = 311,755

Interestingly enough, when the min separation angle is increased, the number of 3D image points that are removed because the separation angle is too low is increased but the number of 3D points that are removed because there are too few image points (fewer than 3) is decreased by about the same amount and the number of 3D points that remain is about the same. In any case, the two dense 3D reconstructions seem to be quite similar, at least, when viewed as animated gifs.