Tuesday, August 23, 2016

Multi View Stereo - Bust of Hadrian

This is an attempt at reconstructing the bust of Hadrian which is proudly exhibited in the "coin room" at the Museum of Fine Arts in Boston, MA. The input to SfM10 is a sequence of 9 images extracted from a video I took with my iphone using Avidemux and rotated 90 degrees using XnView. The image size is 1080x1920.

This is the sequence of images:

This is the input to MVS10:

nvm file = duh.nvm
Min match number (camera pair selection) = 100
Min average separation angle (camera pair selection) = 0.1
radius (disparity map) = 32
alpha (disparity map) = 0.9
color truncation (disparity map) = 20
gradient truncation (disparity map) = 10
epsilon = 255^2*10^-4 (disparity map)
disparity tolerance (disparity map)= 0
downsampling factor (disparity map)= 2
sampling step (dense reconstruction)= 1
Min separation angle (low-confidence 3D points) = 0.1
Min image point number (low-confidence 3D points) = 3
Max reprojection error (low-confidence image points) = 2
Radius (animated gif frames) = 1
Angle amplitude (animated gif frames) = 5

The nvm file is the output of the structure from motion software SfM10. I use a downsampling factor of 2 for depth map generation. Using a downsampling factor of 1 takes too long and using a downsampling factor of 4 is a little bit too loose w/r to the quality of the depth maps produced. A compromise was reached by using a downsampling factor of 2. I use a max reprojection error of 2.0 pixels, which is quite tight. To get a denser 3D reconstruction albeit less accurate, you may want to use something looser (maybe up to 16.0 pixels) and re-run MVS10 (without deleting any mvs file).

This is the animated gif representing the dense 3d reconstruction obtained by MVS10:

This is the sketchfab viewer which enables you to move around the 3D scene: