Check if Polygon is flat on a Plane

On 28/06/2018 at 14:14, xxxxxxxx wrote:
I want to check if a Polygon is flat and 100% on a Plane that is defined by another Objects XYAxis.
How can I do that? I am stuck here. 
On 28/06/2018 at 23:01, xxxxxxxx wrote:
Not sure if this is the most technically and/or mathematically correct solution, but I would check each polygon's vertex normal (=cross product of the vertex with next and previous vertex). If all normals are equal then I would assume the polygon to be flat.
Additionally, when all these normals are equal to the Z axis (= cross product of X and Y axis) of your reference object, then I would assume the polygon AND flat AND 100% on the XY plane of that object. 
On 29/06/2018 at 03:24, xxxxxxxx wrote:
Hi Holgar, thanks for writing us.
With regard to your question, and following C4DS hints, I recommend, given the four points arranged in such a fashion:
AB
 \ 
 \ 
DC
and that to run the following steps: check that the dot product between vectorAB and vectorZ is 0
 check that the dot product between vectorBC and vectorZ is 0
 check that the dot product between vectorAD and vectorZ is 0
 check that the Zvalue of point A matches the Zvalue of your XYaligned plane
Hope these few hints can help you to sort it out.
Cheers, Riccardo