Z persiname 3] 9.5 Perpire s [2] perpframe [1]] -0. 5 y Here's a look at the same plane a point not on the plane: | 0.5 perpframe [1] - 0.5 perpframe [2] {0 . 694101, -0. 121499, 0. 0588317} point = (0. 694, - 0.125, 1.225); pointplot = Graphics3D [{Firebrick, PointSize [0. 03], Point [point] } ]; Show [planeplot, pointplot, PlotRange -> All] ; X 1 Z perparame [3] 0 .5 0 perpiranA [2] perpframe [1] -0 . 5 Y 1 Use perpendicular components to come up with the point on the plane closest to the plotted point