VDS values exploding in certain settings

[ddonatien]

VDS evaluation relies on pycocoeval's evaluate method. This method relies on the ground truth 'area' value used as a denominator (see here).
This value is computed in PointerDataset l 390 and is 0 when the keypoints are aligned with the image's axes (in code x1=x0 or y1=y0).
This results in giving far more influence on the vds measurements for 0, 90, 180° angles rather than 45° angles for instance since in these settings the vds value tends to reach huge numbers.