Shape Threshold
The following ellipse overlap diagrams give some intuition for the meaning of
the shape threshold used in the affine-adaptation experiments. The diagrams
are created by drawing the ellipse for a point in one image and then drawing
the ellipse projected from the matched point in the other image. The second
ellipse is projected thru a known homography between the two images, so if
the affine-adaption found the shape perfectly in both images, the ellipses
should be exactly the same. We measure the error using the union and
intersection of the areas of the two ellipses: error = 1 - (intersection /
union).
The inersection of the two ellipses is painted yellow, while area that
is not in the intersection is painted white. The
perimeters of the ellipses are penned in red and green respectively.
less than 1%
| 
1%
| 
2%
| 
3%
| 
4%
|
5%
| 
6%
| 
7%
| 
8%
| 
9%
|
10%
| 
11%
| 
12%
| 
13%
| 
14%
|
15%
| 
16%
| 
17%
| 
18%
| 
19%
|
20%
| 
21%
| 
25%
| 
28%
| 
29%
|
36%
| 
42%
| 
46%
| 
52%
| 
58%
|
70%
| 
79%
|