CAD Surface Position and Orientation

When FRED imports a CAD model, all of its surfaces are defined by NURBs, or trimmed versions of those NURBs called Trimmed Parametrics. These parametric surfaces are always defined in the global coordinate system. One of the major difficulties with this definition is that the X, Y, Z location of a surface is not easily determined from the parametric definitions, which makes the alignment of these structures with native FRED objects difficult. For more information about CAD coordinate systems, search the knowledge base for the article, “Attaching entities to CAD surfaces”.

The script that accompanies this document identifies the position of a surface in global coordinates by using numerical sampling with rays. A source is created on the selected surface and the ray statistics are retrieved to give average position and surface normal direction in the global coordinate system. Knowing the position and direction of the surface normal is usually enough information to properly align the NURB objects in a FRED model.

Download the PDF: Create-Source-to-Detemine-CAD-Surface-Position.pdf

Download the FRED Script: calculateSurfacePositionOrientation.frs

Download the FRED file: Surface-Source-Emitter.frd