File - Import CAD

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Import CAD

Page Contents

Description

•NURB order and raytrace speed

•IGES object type list

•NURB surface origin

•Set compact / expanded view

Related Topics

Description

FRED imports CAD geometry in IGES or STEP file formats. The import routine constructs objects exactly as they are defined in the CAD file (as NURBs) instead of approximating with a FRED native entity. NURB order can be reduced during import under a tolerancing condition which ensures no more than a maximum given surface height deviation. Reduction of NURB order, when appropriate, can produce a dramatic increase in raytrace speed.

Navigation

This command can be accessed in the following ways:

•Menu > File > Import > Import CAD

•Ctrl + Shift + J

Controls

Control	Inputs / Description	Defaults
Browse...	Select the CAD file to be imported.
Comments	Text comments from imported file.
Summary	Summary of imported file contents.
Destination	Import into a new or existing document.	Current if one is open or new if no document is open.
Import Status	Reports import status.
Import Options
Unassigned Colors	Randomizes colors for imported surfaces and curves.	Unchecked
Independent Curves	Makes and draws independent curves on import.	Checked
Surface Drawing Mode	Draws imported model as "Shaded surface" or "Wire frame (fast)".	Wire frame (Fast)
Default Raytrace Control	Sets the selected Raytrace Control on imported surfaces.	Halt All
Reduce NURB order per tolerance	Reduces the order of imported NURBs to the lowest value for which the maximum deviation between original and approximate surface is less than the given tolerance.	Unchecked
Simplify curves	Attempts to replace NURB curves with native FRED curves.
Move Coordinate System Origin to Surface	Converts the default global coordinate system of NURBs to a local coordinate system on the surface. Location of that local origin is at a position where the parametric coordinates u and v are minimum or the surface average. The following options are available: •Do not move origin to surface •Move origin to surface minimum (U,V) •Move origin to surface average (U,V) NOTE: In the case of some trimmed surfaces, this local origin may not lie directly on the surface.	Do not move origin to surface

Create	Accept settings and keep dialog box open.
Dismiss	Discard settings and close dialog box.
Help	Access this Help page.

Application Notes

Large CAD models

Large models may result in slow response of the 3D view. For convenience, select Wire frame mode to increase video responsiveness and eliminate tesselation delays.

NURB order and raytrace speed

As the order of NURB surfaces increase, so does the required trace time. Photon Engineering recommends reducing the order of NURBs to the lowest possible value consistent with the particular application to enhance raytrace speed.

IGES object type list

FRED internally models objects exactly as they are defined in the CAD file (as NURBs) instead of approximating with a FRED native entity. A list of IGES objects supported by FRED can be used to understand the Summary report.

NURB surface origins

By default, NURBs are imported in the global coordinate system, and as a result NURBs do not have a local coordinate system affixed to their surface as all other FRED surfaces do. By selecting the "Move Coordinate System Origin to Surface" options, FRED endows each NURB with a local coordinate system. This local coordinate system origin is located at a point where the parametric coordinates U and V are minimum or at the surface average. In the case of some trimmed surfaces, the local coordinate origin may not lie directly on the surface but will be in the near vicinity.

Shown in the following image is a FRED surface (top) which has been exported into a CAD format and re-imported into FRED using each of the three different coordinate system origin specifications (bottom). In these images the arrow object's position/orientation specification is set to be located at the origin of the NURB surface (B-Spline Surface 2). Unless otherwise specified, the default origin of the imported NURB surface will be at the Global origin (bottom left). If the option "Move origin to surface minimum (U,V)" is selected on import then the surface origin will be located where the NURB surface parameterization is a minimum value (bottom middle). If the option "Move origin to surface average (U,V)" is selected on import then the surface origin will be located where the NURB surface parameterization has the average value (bottom right).

Note that in the Geometry folder of the object tree, the imported surface is of type 'TrimSurf". The actual base surface of the TrimSurf can only be seen by right mouse clicking on the TrimSurf and selecting the option, "Trimmed Parametric Surface Set Expanded View (recursive)". The B-Spline (untraceable) surface is the base surface to which the analysis surface should be attached.

Set compact / expanded view

Geometry imported from a CAD file (IGES or STEP) can be displayed in a Compact State in the Tree Folder. This option streamlines the folder by hiding base surfaces and trimming curves. Set this option by right-clicking at any level of the Tree. Note that this option is recursive, acting on all entities in the heirarchy below the level at which the Compact/Expanded State is set.

Expanded View

Compact View