Hi, I am designing an application which uses DXF files and I have to interpret DXF data concerning NURBS ("SPLINE" command in AutoCAD). I have mathematical background of them, but I don't know how to incorporate values of knot, control point and fit tolerances (group codes 42, 43 and 44 in DXF file) into curve equations. I will be very grateful for some references and information explaining this problem. S³awek Kacprzykowski