CAT Direct Connect Reference

Overview

The Alias CAT Direct Connect product allows the exchange of 3D model data between Alias and CATIA using the CATIA/Alias neutral format CAI. There are two interfaces for the product:

• a graphic interactive interface via the standard file import/export capability within the Alias Studio-based interactive products

• a UNIX command-line interface designed to facilitate batch conversion of data files.

This section contains information on:

• Interactive User Interface on page 112

• Unix Command Line Interface on page 118

• Translation Log File on page 119

• Supported Geometry and Data Mapping on page 130

Interactive User Interface

Importing and exporting a CAI file is as simple as importing and exporting any geometry file into Alias. Please refer to the File Operations section in the Basic Tools in Alias book for information on importing a file into Alias. The following subsections contain information specific to importing and exporting a CAI file.

Importing a CAI File

You can import a CATIA CAI file into Alias by selecting File > Open or File > Import File.

Linear Units and Tolerances

As a first step in the CAI file import process, the linear units and tolerances stored in the CAI file are examined and compared with the current linear units and tolerances in the Alias modeler. The linear units and tolerances stored in the CAI file are those that were used by CATIA in the creation of the geometry in the CAI file.

If the linear units stored in the CAI file are different than those in Alias, a confirm window is displayed indicating both CATIA and Alias linear units.

You are asked if you want to change the current Alias linear units to those stored in the CAI file. If you select YES , the current Alias linear units are changed to the units indicated, and processing continues. If you choose NO , the current Alias linear units do not change and the translation process continues. If you choose CANCEL , then the current Alias linear units do not change and the translation process is aborted.

If the tolerance stored in the CAI file is different from that of the current Alias modeling tolerance, a confirm window is displayed, containing both the CATIA Curve Tolerance from the CAI file and the corresponding current Alias Curve Fit Distance Tolerance.

You are asked if you want to change the current Alias Curve Fit Distance Tolerance to be the same as the CATIA Curve Tolerance stored in the file.

CATIA Import Options

View File Info

When you turn this option ON , any user information contained in the imported file is displayed in a confirm window. After reviewing this information, you can choose to continue with the translation by selecting OK , or abort the translation by selecting CANCEL .

The Comment File is one of the pieces of information included in the File Info . The Comment File is a text file where you can input information pertaining to the development of a project. In addition, if the import of a CAI file is completed with an included comment, then that comment will be added to the existing Comment File.

Browse Log File

This option controls the automatic display of the import translation log file once the transfer has been completed. If you turn this option ON , the log file will be displayed in an editor window after the translation has been completed. (Please see the Translation Log File section on page 112 for more information on the log file name and format).

Extended Log File

This option controls the generation of a verbose log file. The log file is always produced. If you turn this option ON , the log file includes detailed entity mappings, Info , Error and Warning messages, and entity count tables. If you turn this option OFF , then the terse form of the log file is generated. It contains Info , Error and Warning messages, and entity count tables only.

Exporting a CAI File

Export a CAI file from Alias for import into CATIA by selecting File > Save As or File > Export > Save Active and selecting CATIA from the File Format popup window.

The filename extension CAI will be added to the specified filename on export. This file extension is required by CATIA. A log file containing details of the translation process is produced for both import and export.

CATIA Export Options

Browse Log File

See CATIA Import Options on page 114 for more information on controlling the display of the export translation log file.

Extended Log File

See CATIA Import Options on page 114 for more information on controlling the contents of the export translation log file.

Include Comments

This option controls the display of user-supplied comments in the exported CAI file. The CATIA file comment is restricted to 70 characters per line and a maximum of 500 lines.

Because Edit Comment uses a user-defined editor, you are not bound by these limits; however, the file comment that is exported from Alias will change to conform to these restrictions, if necessary. That is, lines over 70 characters in length will be wrapped and the comment will be truncated at 500 lines.

CATIA File Header Information: Edit File Header

When you click on this field, the CAI File Header Information window is displayed. In this window, you can provide a short comment that might include a description of the model, the name of your organization and company, an authorization code, and your name as the author of the exported model. Entering information in this window is optional.

CATIA File Header Information: Edit File Comments

When you click on this field, an editor window appears. In it, you can type more detailed comments about the model. The comments are included in the exported file only if you select the Include Comments option.

The CATIA file comment is restricted to 70 characters per line and a maximum of 500 lines. Since Edit Comment uses a user-defined editor, you are not bound by these limits; however, the file comment that is exported from Alias will be altered to conform to these restrictions, if necessary. That is, lines over 70 characters in length will be wrapped and the comment will be truncated at 500 lines.

Unix Command Line Interface

The utilities CaToAl and AlToCa provide the Alias CAT Direct Connect translation functionality at the UNIX command line level. As in the interactive versions, these utilities produce either a brief or extended log file. The log file can also be displayed on the screen during translation.

CaToAl

This utility converts a CAI file to an Alias Wire File. To display the usage information, type the following in a UNIX shell window:

CaToAl -h 

The usage information will be printed as follows:

CaToAl - Convert CAI (CATIA/Alias Interoperability) 
files to wire files.

CaToAl [-h] [-b] [-x] 

   -i<InputCAIFile> -o<OutputWireFile>

AlToCa -h 

AlToCa - Convert Alias Wire files to CAI (CATIA/
Alias Interoperability) files.

    Trimmed Target Surface node#13 converted to 
FaceElement <NONE> #341



                                                CrvSrf 
<NONE> #354



    Trimmed Surface node#12 converted to 
FaceElement <NONE> #356



    Trimmed Surface node#11 converted to 
FaceElement <NONE> #371



    Trimmed Target Surface node#10 converted to 
FaceElement <NONE> #386



                                                CrvSrf 
<NONE> #403

The following sections describe the mapping process used for geometry types and non-geometric data that can be transferred between Alias and CATIA via the CAI file.

Supported Alias Geometry Types

The following Alias geometry types can be exported to CATIA. Non-geometry entities such as Lights, Cameras, Textures, Windows, Shaders and Animation are not supported by the translator. The numbers in the table entries refer to Notes For Table 1 below.

Alias Entity	CAI File Entity	CATIA Entity
Construction Plane	Axisbold(1)	8.1 3-axis system
Polyset	Not supported at this time.	N/A
Arc	RationalCurve	46.1 Rational B_spline curve
Circle	RationalCurve	46.1 Rational B_spline curve
Line	Line (partially supported) bold(2)	2.1 space line
Curve	BsplineCurve RationalCurve	3.2 B_spline polynomial space curve 46.1 Rational B_spline curve
Face	FaceElement bold(3)	6.1 face
Surface	BsplineSurface RationalSurface	5.2 B_spline polynomial surface 47.1 Rational B_spline surface
Target Surface	CrvSrf bold(4)	12.1 edge (curve on surface)
Trimmed Surface	FaceElement bold(5)	6.1 face
Trimmed Target Surface	FaceElement and CrvSrf bold(6)	6.1 face and 12.1 edge (curve on surface)
Shell	OpenShell	13.1 skin

Notes For Table 1

1

The scale component of the Alias Construction Plane is not transferred. That is, its orientation and position will remain the same, but its size will not. After a round trip translation (Alias \> CATIA \> Alias), an Alias Construction Plane with original scale values Sx, Sy, and Sz, will return with scale values of 1, 1, 1.

2

An Alias Line created by Curves > Line and related tools is not supported on export to CAI as a CAI Line primitive, but is supported as a CAI BsplineCurve. However, on import to Alias of a CAI Trimmed Curve whose basis curve is a CAI Line (this maps to a CATIA limited Line), an Alias Line is created. Such a Line will be exported as a CAI Line. This ensures the original CATIA limited Line is preserved.

3

An Alias Face element is converted to a Trimmed Surface temporarily and then exported as such (see note bold(5) below).

4

An Alias Target Surface contains one or more Curves-on-Surface. A CrvSrf entity is exported for each curve-on-surface. On import to Alias, multiple CrvSrf entities that reference the same base surface will be converted to one Alias Target Surface containing multiple curves-on-surface that correspond to these CrvSrf entities.

5

An Alias Trimmed Surface is exported as one or more FaceElements (one FaceElement for each region of the trimmed surface). On import to Alias, multiple FaceElement entities that reference the same base surface are converted to an Alias Trimmed Surface, with multiple regions corresponding to these FaceElements.

6

An Alias Trimmed Target Surface also contains curves-on-surface that have not yet been used for trimming. Similar to the descriptions in Notes 2 and 3, it is exported as a combination of CrvSrf and FaceElement entities.

Supported CATIA Geometry Types

The following CATIA geometry types can be imported to Alias. The letters and numbers in parentheses refer to Notes For CATIA Entities in Table 2 and Notes For Alias Entities in Table 2, respectively, below.

CATIA Entity	CAI File Entity	Alias Entity
8.1 3-axis system (fixed)	Axis	Construction Plane
1.1 space point	Point	Curve and Locator bold(1)
2.1 space line bold(1)	Line	Line
3.1 polynomial space curve bold(1) 3.2 B_spline polynomial space curve bold(1) 20.1 space circle bold(1) 21.1 space ellipse bold(1) 22.1 space parabola bold(1) 23.1 space hyperbola bold(1)	BsplineCurve	Curve
46.1 Rational B_spline curve bold(1)	RationalCurve	Curve
4.1 plane 4.24 plane bold(2)	Plane	Surface bold(2)
5.1 polynomial surface 0 unspecified 1 sphere 2 cylinder 3 cone 4 torus 5 unspecified surface of revolution 6 tabulated cylinder 7 ruled surface	BsplineSurface	Surface
5.2 B_spline polynomial surface	BsplineSurface	Surface
47.1 Rational B_spline surface	RationalSurface	Surface
12.1 edge (face boundary) bold(3)	OrientedEdge	Trim Curve bold(3)
12.1 edge (curve on surface)	CrvSrf	Target Surface bold(4)
6.1 face	FaceElement	Trimmed Surface bold(5)
13.1 skin	OpenShell	Shell
7.1 volume bold(4)	OpenShell(s)	Shell(s)
17.2 exact solid bold(5)	OpenShell(s)	Shell(s)
28.1 space ditto	Ditto	Instance bold(6)

Notes For CATIA Entities in Table 2

1

For all CATIA curves whose limits have been modified, a CAI Trimmed Curve instance may be created when exporting.

2

For CATIA planar faces, some 4.24 planes may be transferred as they are used as the base face surface.

3

The curve associated with the edge in CATIA is converted into a B-spline Curve, used by the Oriented Edge. The parametric definition of the CATIA edge is converted to a B-spline Pcurve used by the Oriented Edge.

4

The domains of the CATIA volume are converted to open shells.

5

The Boundary representation of the solid is extracted and converted to CAI elements (open shells, curves, etc.). Prior to exporting the exact solid, make sure that this solid is up-to-date.

Notes For Alias Entities in Table 2

1

A CAI Point is converted to a degree 1 curve composed of two coincident points and a Locator that identifies the location of this curve. On export to CAI, this construction is converted back to a CAI point.

2

A CAI Plane describes an infinite plane and is converted to a unit Alias Surface. This Surface will be re-exported as a CAI Plane.

3

The CAI Oriented Edge maps to a trim curve of a trimmed region of an Alias Trimmed surface.

4

A CAI CrvSrf entity maps to one Alias curve-on-surface for a particular surface. Multiple CAI CrvSrf entities in the CAI file referencing the same surface will cause multiple Alias curves-on-surface to be added to one Alias Target Surface.

5

A CAI FaceElement maps to one region of an Alias Trimmed Surface. If multiple CAI FaceElements in the CAI file reference the same surface, then an Alias Trimmed Surface will be created with multiple regions.

6

A CAI Ditto is imported as an Alias instance node, with the CAI Ditto transformation, of the Alias group representing the CAI Detail (see Supported Non-Geometric Data, Groups/Instances below).

However, if at least two CAI Dittos of the same CAI Detail each belong to different parent CAI details, then those dittos are "exploded". That is, each geometric entity of the detail is copied and transferred by the transformation of the CAI Ditto.

Supported Non-Geometric Data

The following non-geometric data can be imported and exported between Alias and CATIA.

Groups/Instances

How an Alias Group is exported depends on whether it is instanced or not. An Alias Group that is not instanced has its component geometry exported to the appropriate independent CAI geometric entities. An Alias Group node that is instanced is exported as a CAI Detail entity (that is, the grouped Alias geometric entities become members of the CAI Detail); an Alias Instance node is exported as a CAI Ditto entity. CAI Dittos and Details are subsequently imported into CATIA as CATIA Dittos and Workspaces, respectively.

An Alias Instance that contains a non-proportional (non-p) scaling factor in its transformation is "exploded" on export (that is, each geometric entity that belongs to the Alias Group being instanced is copied and transformed to independent CAI geometric entities). Only instances that contain a non-p scale component are exploded. Other instances of the same group that do not have a non-p scale component will export as CAI Dittos of a CAI Detail (as noted above).

CATIA Workspaces and Dittos can feature a situation that is not supported by the Alias dag structure and instancing mechanism. This situation arises when Dittos of the same Workspace belong to different parent Workspaces (see note bold(6) in Notes For Alias Entities in Table 2 above). The CATIA Ditto/Workspace structure is preserved as best as possible on CAI export from CATIA and subsequent import back to CATIA.

Names

Alias DAG node names are exported as an attribute of the CAI entity to which the node's geometry maps. Alias Instance node names are exported as an attribute of the CAI Ditto; the corresponding CAI Detail will have the name of the instanced Alias Group node. The name attribute of a CAI entity is mapped to the CATIA User Identifier for that entity in CATIA.

On CAI import to Alias, it is possible for multiple CAI entities to map to a single Alias object (see notes bold(4) and bold(5) in Notes For Alias Entities in Table 2 above). Each of these CAI entities may have a unique name (CATIA User Identifier), but the Alias object can only have one name available for viewing and editing. The CATIA User Identifiers that are not mapped to an Alias object with a modifiable name are maintained by Alias for subsequent export to CATIA via CAI, assuming the objects to which the names are assigned still exist.

For example, a CATIA user can name individual Faces that all reference the same surface. These Faces map to CAI FaceElements which in turn map to trim regions of a single Alias Trimmed Surface. Only the trimmed surface node can have a name, and this is given the name of the underlying CATIA surface being trimmed. The CATIA User Identifiers of each of the faces that mapped to trim regions are maintained within Alias so they can be transferred back to CATIA. A similar situation exists for multiple CAI CrvSrf entities that map to one Alias Target Surface. The CAI CrvSrf name attribute is preserved for export back to CATIA.

Alias generated names of the form node#<n> (for example, node#5) are not exported to CAI. CATIA generated names of the form *<OBJ><N> (for example, *FAC5) are not exported to CAI. CAI entities that do not have names are given a system generated name on import to Alias or CATIA.

Layers

The Alias Layer assignment is preserved when exporting to CAI. As with names, the layer number becomes an attribute of CAI geometric entities and Dittos. The layer name and other Alias Layer attributes are not exported.

On CAI import to Alias, geometric entities are placed on the layer defined by the CAI layer number attribute. If the layer is created by the import process, it is given the name CATIA_<N> where <N> is the layer number. All layers created by the CAI import process are sorted in the layer bar by ascending number.

As with the name attribute, the layer number assignment for CAI FaceElement and CAI CrvSrf entities is preserved on CAI import so that this information can be returned to CATIA through CAI even though it cannot be modified in Alias.

In Alias, a geometric object and all of its ancestors in the dag hierarchy must be in the same layer. In CATIA, this is not necessarily the case, as a Ditto may be in a different layer than the components of the instanced Workspace. On CAI import to Alias, this feature of CATIA layers is maintained for subsequent export back to CATIA. If you change the layer assignment of an Alias Instance that was created from a CAI Ditto, you will change the layer assignment of all the geometric entities being instanced to this new layer number within Alias. However, on CAI export, the original CATIA layer number assignments for the component geometric entities and Ditto will be used.

CATIA Dittos that are not assigned to a layer will be preserved through a bi-directional CAI translation with Alias. While in Alias, these Dittos will be imported as Alias instances that reside in the Default Layer.

Object Colors

The wireframe display color of CATIA objects is preserved in a bi-directional CAI translation with Alias, providing the CATIA model uses the CATIA Standard Color Table. If the model references a user-defined color table, then on CAI import to CATIA, the CAI color of each element is chosen from the standard color table as the closest match to the original color.

As with names and layers, the CATIA wireframe color index of an object is an attribute of the CAI geometric entity. On CAI import to Alias, the CAI geometric entity's color index is converted to an RGB color based on the CATIA Standard Color Table. This RGB color is used to create a simple shader that is assigned to the associated Alias object that is created, unless the object is a curve. Only for curves is the CATIA wireframe color index preserved. CAI surface geometry that has no CAI color attribute is assigned the Alias default shader.

On Alias export to CAI, the color index of a CAI geometric surface is determined by finding the index in the CATIA Standard Color table that represents the closest match to the RGB color of the associated Alias shader. For non-surface CAI entities, the preserved CATIA color index is exported if it exists. For original Alias curve geometry, the layer color is used to find a close match to a CATIA Standard Color index.

Layer Colors

Layer colors are not transferred explicitly via the CAI format. However, layer colors are assigned to layers created as a result of CAI import by one of two possible methods.

In the first method (the default) a created layer is assigned one of the 15 available colors based on the remainder of the layer number divided by 15. This cycles through the available Alias layer colors as the layer number increases.

The second method uses the CATIA Standard Layer Color Table which is defined in the CATIA environment's startup initialization file CATINSTD.dcls. If this file exists in the /usr/aw/alias/.Alias/ directory of the Alias installation, or in the .Alias/Prefs.1/Color/ directory of the Alias user account, then the CATIA Standard Layer Color Table will be extracted from this file by the Alias CAI import process and used in the layer color assignment process.

The CATIA Standard Layer Color Table assigns to each of the 256 CATIA layers a default CATIA color index whose RGB color is defined in the CATIA Standard Color Table (see Object Colors above). When the Alias CAI import process has access to this default layer color assignment, it assigns a color to a newly created Alias layer that closely matches the color for that layer number in the table.

To activate this second method copy the CATINSTD.dcls file from the CATIA installation to /usr/aw/alias/.Alias/ or to the .Alias/Prefs.1/Color directory of your user account. Alternatively, create a symbolic link, in either of these Alias directories, to the CATINSD.dcls file in the CATIA installation.

For example, if Alias is installed in /usr/aw and CATIA is installed in /usr/catia, then the following command will create the necessary symbolic link:

ln -s /usr/catia/cfg/dec/CATINSTD.dcls /usr/aw/alias/.Alias/CATINSTD.dcls