Hi

I'm a newbie to all this, so I hoping someone can point in the right

direction. I have a rectangular region (R) that lies in a 3D

coordinate system.

I have the location of the upper left hand corner of R, point

P(a,b,c).

I also have six directional cosines. One set of three (dcx1,dcy1,dcy1)

pertain to one vector V1, that originates from P. The other set of

three (dcx2, dcy2, dcz2) pertain to the vector V2, that orignates from

P and is perpendicular to V1. V1 and V2 from the boundaries of one

corner of the region R.

V1

P-----------------|

| X |

V2 | |

|-----------------|

Given a 2D point X (x1,x2) in the local space of the region R, I want

to determine its location in the 3D global space.

I came up with the following

M = |dcx1, dcx2,0,a |

|dcy1, dcy2,0,b |

|dcz1, dcz2,0,c |

3DPoint = M * [x1,x2,0,1]

Is this correct?

Also how what would I have to do to go the other way? That is, given

a 3D point that I know is on R, I have to determine a 2D point in the

space of the region.

Thanks!