SolidKit3D.Math3D.LinePlaneIntersection
From Solid Graphics Wiki

The LinePlaneIntersection function calculates a line's intersection with a plane.
public static float LinePlaneIntersection ( ref Point rStart, ref Point rEnd, ref Plane plane, out Point ip );
Parameters
lStart  x,y,z coordinates of line's first definition point. 
lEnd  x,y,z coordinates of line's second definition point. 
plane  four float/double values defining the plane. 
ip  if the line intersects the plane then the function will put coordinates of the intersection point to ip. 
Return Value
The function returns float.MinValue if the line does not intersect the plane. If the line intersects the plane then the function returns position of the intersection point on the line. The position can be then translated to point coordinates using the LinePositionToPoint function.
See Also