[CIM/Infor-Base] Understanding the Constraint Entity(Path)

Question 

Please describe the Constraint Path.

Answer 

Constraint Path serves as a reference target when creating an object that references a path, such as a Curve Library or Path Linked Entity, and serves as a reference target when creating another Constraint Entity.

In CIM, there is an object called Constraint Entity that is responsible for only the constraint of the model apart from modeling that determines the shape.

This structure captures the common constraint information of various objects created during modeling. It is advantageous to control the model because it can be integrated and managed by linking to one Constraint Entity. Therefore, in order for CIM's alignment-based modeling to work as intended by users, an understanding of Constraint Entity is required.

The Constraint Entity of CIM is as follows, and this FAQ deals with the Constraint Path.

<Type of Constraint Entity>

Expression Entity linked to Constraint Path property is only applicable to Path Linked Entity created by
Curve Library Mode   : Expression Entity > Path Linked function or
Assembly Unit Mode : Expression Entity > Path Linked function.

Similarly, Expression Entity linked to Constraint Point properties is a library created as
Single Point or Multi-Points in Point Library Mode,
Curve Library Mode: Expression Entity > Point Linked function, or
Assembly Unit Mode : Applicable only to Point Linked Entity created by Expression Entity > Point Linked function .

The Constraint Path is an essential object in CIM (Common Information Model) layout-based modeling. The role of the Constraint Path is as follows

Role of the Constraint Path

Depending on how a Constraint Path is defined in Curve Library/Assembly Unit Mode, the entire model will determine how to respond when assigned to a layout. The characteristics and uses of Constraint Paths are as follows

Each Constraint Path is related to the following objects.

Main Path

Property of Main Path

Objects affected by Main Path

Figure 1. Constraint Plane > Main Path

The start/end points of the Main Path's Property define each Constraint Plane selected when created.
Therefore, the two objects have a dependent relationship, and the X coordinate value of the start/end point of the Main Path is determined by the location (X coordinate value) of the Constraint Plane. (The two values are the same.)

The Y/Z coordinates of each point, except for the X coordinate, are defined by the Offset value of the Property.

Objects which affect Main Path

Figure 2. Main Path > Constraint Point

Figure 3. Main Path > Constraint Array Point

Figure 4. Main Path > Rigid Path

For Constraint Point and Constraint Array Point, each depends on one Main Path, and the values of Location/Alignment/Arrangement operate.
Therefore, after Layout is assigned, position definition is made for the Geometry of the corresponding Main Path

The Main Path is utilized as the standard Path for tracking two Coincident Points after Layout assignment for the Rigid Path.

Rigid Path

Property of Rigid Path

Objects affected by Rigid Path

Figure 5. Constraint Path & Constraint Point > Rigid Path

The Rigid Path creates a path with a fixed length by connecting two coincident points.
The two coincident points are tracked on the constraint main path defined in the property.

The coincident point references the reference location defined in the property, which can be a constraint point or constraint plane, and follows the location of the corresponding object.

Objects which affect the Rigid Path

Figure 6. Rigid Path > Constraint Point

Points can be created on the Rigid Path.
The constraint point created by referring to the Rigid Path cannot be selected as a reference point for other Rigid Path creations.

Sub Path

Sub Path Property

Objects affected by the Sub Path

Figure 7. Constraint Point > Sub Path

The start and end points of the sub path move based on the Constraint Point defined at creation.
The reference point and each point of the sub path may not necessarily match because of the input X/Y/Z offset value at creation.

This offset value can be set to follow the Path vector coordinate system or the GCS/UCS coordinate system through the Alignment setting.
The Path vector is determined by the vector connecting the two constraint points.
(if the same Constraint Point is selected for Start and End, then the tangent vector of that point).

Object which affect Sub Path

There is no Constraint Entity created by referring to Sub Path information.