How to derive BB-related virtual properties¶
BB-related virtual properties are essentially a group of virtual columns derived from either
BBS or BBSpredicted or both. These virtual properties can be used the same way as
the collected BB metrics. All available virtual properties are listed under Derive virtual column in the popup menu
when RightClick’ing a selected bounding box column.
Some commonly used virtual properties of BBS or BBSpredicted include:
Rectangles(absolute): An array of four absolute values in form of [min_x, min_y, max_x, max_y] for each BB
Rectangles(relative): An array of four relative values in form of [min_x, min_y, max_x, max_y] for each BB
Area: Area for each BB
Aspect: Aspect ratio for each BB
Height: Height of each BB
Width: Width of each BB
Overlap ratio: Sum of overlapped areas of a given BB with all other BBs divided by area of this BB; value can be greater than 1
Unique overlap ratio: Sum of unique overlapped areas of a given BB with all other BBs divided by area of this BB; value is equal to or less than 1
Some commonly used virtual properties derived from selecting both BBS and BBSpredicted include:
IoU: Intersection over union between ground truth and predicted BBs. This is an order-dependent virtual column, which means that it will be computed on the basis of and assigned to the first selected column.
FN: False negatives with default 0.5 of IoU threshold, which is adjustable; FNs are assigned to ground truth BBs regardless of the selection order of the two columns.
FP: False positives with default 0.5 of IoU threshold, which is adjustable; FPs are assigned to predicted BBs regardless of the selection order of the two columns.
TP: True positives with default 0.5 of IoU threshold, which is adjustable; TPs are assigned to predicted BBs regardless of the selection order of the two columns.
Sum: a chained property under FN/FP/TP; it can be used to calculate the total FNs/FPs/TPs for each sample.
To adjust the IoU threshold for FN/FP/TP, select the derived FN/FP/TP column, RightClick and hover
over Tweak virtual column, and then adjust the value either by typing in the box or dragging the slider.
FN/FP/TP/IoU: virtual properties vs collected metrics
Like all virtual columns created in the Dashboard, FN/FP/TP/IoU virtual properties are dynamic and re-computed e.g. as ground truth BBs are edited or IoU thresholds are adjusted. On the other hand, you may have collected FN/FP/TP/IoU metrics during metrics collection that you are also able to display in the Dashboard. Keep in mind that such metrics are static (e.g. they will have the fixed IoU threshold used when collected) and they cannot be changed in the Dashboard. The dynamic character of the Dashboard virtual properties makes their use especially versatile and flexible.