The results are different in Quad mode , is it a bug ?

[finscn]

I know when the quadrangle become a concave polygon , the result will be unexpected.

But I think the results should be under the same rule.
I mean the 4 results in the image , they are should be mirror in X/Y.

( In other lib about projection , the first one is used. )

[finscn]

I know this issue is similar to #4 ,
but the key point in this issue is the four results are different ,
the key point in #4 is the result is unexpected

[ivanpopelyshev]

Order of points is important here.