CvKNearest Circular(angle) nearest neighbor

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In the CvKNearest class,there is the find_neighbors_direct method to find circular nearest neighbor is used and receives two parameters start and end(for example start =0 & end=360 they are neighbors). there is also the find_nearest method to find regular nearest neighbors.

My Features :

I have 3 features x , y ,theta .the x & y features are regular & theta feature is circular(direct).

My Question:

How can find 3 features together & Simultaneously.