GLua code to compute the intersection of a line with a plane. Used for determining where a player is looking on a 3D2D Screen

glua-line-plane-intersection.lua

-- l0 is the origin of the line
-- l is the direction of the line expressed as a normal vector (tbd: does it have to be normal? possibly not)
-- p0 is the origin of the plane 
-- n is a vector orthogonal to the surface of the plane expressed as a normal vector (tbd: does it have to be normal? possibly not)
function vectorIntersectPlane(l0, l, p0, n)
    -- we find d by substituting the equation for the line into the equation of the plane and solving for d
    d = (p0 - l0):Dot(n) / l:Dot(n) -- distance along the line at which the line intersects the plane 
    
    -- the point of intersection is found by substituting the distance back into the line equation
    -- p = dl + l0 
    return d * l + l0 
end