Biomedical Engineering Reference
In-Depth Information
Figure 1.8: The spin image generation process can be visualized as a sheet
spinning around the oriented point basis, accumulating points as it sweeps space.
The term “spin-map” comes from the cylindrical symmetry of the oriented
point basis; the basis can spin about its axis with no effect on the coordinates
with respect to the basis. To create a spin image, first an oriented point on the
surface is selected. Then for each other point on the surface, the spin-map pa-
rameters are computed. These parameters are then accumulated in a 2D array.
Once all the points on the surface have been processed, the 2D array is converted
into a gray image. Figure 1.8 shows the spin-image generation process and vi-
sualizes it as a sheet spinning around the oriented point basis, accumulating
points as it sweeps space. Figure 1.9 shows examples of spin images generated
for the surface of a statue. The darker the pixel, the higher the number of points
projected into this location.
They compared spin images using linear correlation coefficients. They used
the magnitude of the correlation coefficients as well as the confidence in the
correlation results which is measured by the variance of the correlation coeffi-
cient. They also modeled the effect of clutter and occlusion to predict a lower
bound on the correlation coefficient.
