Angular Dimensions

DRAW Reference Manual

Dimensions : Angular Dimensions

DRAW functionality contains features that are unique to Angular Dimensions.

The simplest type of Angular Dimension (ADIM) consists of a pair of directions in the 3D model (the dimension directions) that radiate out from the dimension origin. These directions are projected onto the drawing and are represented by projection lines. Between these lines a dimension arc is drawn centred upon the dimension origin. Each dimension arc and projection line can have a piece of text associated with it.

The dimension origin can either be defined explicitly by attributes of the ADIM or implicitly by the intersection of two dimension directions.

The example illustrates an Angular Dimension with its origin defined as a Nozzle in the centre of the vessel. The two dimension directions are both defined as directions from the ADIM's origin to the origins of Nozzles. The Angular Dimension can be created by typing commands, starting at Layer level:


NEW ADIM	- Create new Angular Dimension element.
ON ID @	- Use cursor to nominate the Design item used as the Dimension's origin (a NOZZ here)
FROM @ TO ID @	- Use cursor to nominate Design items defining the first and second Dimension Directions (both NOZZ here).
DPOS @	- Use cursor to nominate a Sheet position through which the Dimension Arc passes.

Having pressed Enter when the confirmation command line displays, the Dimension displays. A pair of Dimension Direction elements are created, with the last direction becoming the current element.

In this example the ID @ commands can all be replaced by IDP @. P-points can then be nominated instead of Design items.

The ON command sets the DDNM attribute of the ADIM to the name of the Design element at the Dimension origin. The NPPT attribute of the ADIM is set to the nominated p-point. If none is defined (as in this example) NPPT is set to a default value that equates to the origin of the element named by the DDNM.

In this example the Dimension Directions are DPPT elements: these also have DDNM and NPPT attributes. In this case DDNM is set to the name of the Design element specified by the FROM or TO keyword, and NPPT to the nominated p-point (or the origin by default).

The DPOS @ command, which allows the position of the Dimension Arc to be defined, sets the DPOS attribute of the Angular Dimension. Alternatively the Arc radius can be defined by setting the Dimension's DOFF attribute. For convenience both these attributes can be set at members of the Angular Dimension. They are mutually exclusive: setting one causes the other to be unset.

For the Angular Dimension in the example, the Q DESCription command typically gives:

On /C1101-N6
Dimension points
1 DPPT From /C1101-N1
2 DPPT To /C1101-N10

The example displays an Angular Dimension with its origin defined implicitly by the intersection of the two Dimension directions, which are plines of SCTNs. The Angular Dimension can be created by typing commands, starting at Layer level:


NEW ADIM	- Create new Angular Dimension element.
FROM DIR IDPL @ TO DIR IDPL @	- Use cursor to nominate plines defining the first and second Dimension Directions.
DPOS @	- Use cursor to nominate a Sheet position through which the Dimension Arc passes.

Having pressed Enter when the confirmation command line displays, the Dimension displays on the display. The position of the Dimension's origin is automatically calculated from the intersection of the two Dimension Directions. A pair of Dimension Direction elements are created, with the last direction becoming the current element.

In this example the DIR IDPL @ commands can be replaced by either of:

•

DIR IDP @ in which case the nominated p-points are used to define directions;

•

DIR ID SCTN @ in which case the NA pline of the nominated SCTN is used.

In this example the DDNM and NPPT attributes of the ADIM are left unset. The Dimension Directions are APPT elements: these have DDNM, PPDI, and PKEY attributes. In this case DDNM is set to the name of the Design element specified by the FROM or TO keyword, and PPDI or PKEY to the nominated p-point or pline as appropriate. PPDI and PKEY are mutually exclusive: setting one causes the other to be unset.

Plines and p-points define specific directions (for example, UP) but in some cases when defining Angular Dimensions it is the 'reversed' direction that is required (for example, DOWN). You can achieve this with the use of the REVDIR attribute of APPTs. By default this is False (or OFF) and the direction of the specified pline or p-point is not reversed when drawing the Angular Dimension. If the reversed direction is required it must be set True (or ON).

When using two intersecting APPTs to define an Angular Dimension there are four possible quadrants in which the Dimension Arc is drawn. All four possibilities can be obtained by setting the two REVDIR attributes appropriately. However the required result can be achieved automatically by setting the DPOS attribute. From the DPOS coordinates DRAW calculates and sets the REVDIR attributes of the two APPTs.

For the Angular Dimension in the example the Q DESCription command typically gives:

Position unset
Dimension points
1 APPT From Direction Ppline NA of /F-2
2 APPT To Direction Ppline MEML of /F2-BRAC-1 Reversed

Note:

The direction of the second APPT has been reversed by the action of the DPOS @ command so that the Dimension Arc is drawn in the required quadrant.

The other types of Dimension Direction that can be owned by an ADIM element are:

•

DPOI allows the direction to be defined by any given 3D position

•

ADIR allows the direction to be defined by any given 3D direction

DPOI elements can be created by a sequence, for example:

NEW ADIM
ON ID @
FR POS @ TO POS @

The FROM and TO commands set the POS attribute of each DPOI to the position defined by the cursor.

ADIR elements can be created by a sequence, for example,:

NEW ADIM
ON ID @
FR DIR N30E TO DIR S20W

The DIR attribute of each ADIR is set to the specified direction.

In each example, the FROM keyword defines the Direction at the start of the Dimension's member list, TO defines a Direction after the last item in the list. The Directions are drawn in the order in which they display in the list, and the rotational direction between the Directions is determined by the minor arc between the first two Directions.

The examples indicate the easiest way of creating ADIM elements, but many other methods are available. The dimension origin can be defined explicitly as a 3D point, as a p-point, as a proportional distance along a pline, as a Branch Head or Tail, or as (the origin of) any Design element.

The example illustrates a multi-valued chained Angular Dimension.

Such a dimension is created in a similar way to a chained Linear Dimension. Notice how the Dimension Arc text is (automatically) oriented and positioned relative to the Dimension Arc so as to make it easiest to read.

In this example the PLTX attribute of the ADIM is set to '#DIMDIR' and as a result the dimension directions display as projection line text. #DIMDIR is an example of an intelligent text codeword. Refer to Intelligent Text for further information. #DIMDIR is valid in the PLTX of ADIM elements and their four potential member types.

For the Angular Dimension in the example the Q DESCription command typically gives:

On P 0 of /C1101-N6
Dimension points
1 DPPT From /C1101-N1
2 DPPT To P 0 of /C1101-N8
3 ADIR To E
4 DPPT To /C1101-N10
5 DPPT To P 0 of /C1101-N12

Additional 'links' can be inserted in or added to a chained Dimension (or a single-valued Dimension can be 'converted' to a chained Dimension) by using the INSERT command in a similar way to Linear Dimensions.

The SORT DIM command can also be used with Angular Dimensions to reorder any incorrectly ordered Directions.

The example illustrates a parallel Angular Dimension.

A parallel Dimension can be produced by setting the LCHA attribute of an ADIM to False (a chained dimension has LCHA True).