Details of annotation elements

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This page belongs to the Recommended Practices for the Presentation of GD&T.

Styling annotations

A subtype of annotation_occurrence defines styled annotations. Within the scope of this effort all annotation_occurrence entity data types will be instantiated as complex instances, since annotation_occurrence entity data types are subtypes of both a draughting_annotation_occurrence and a styled_item.

The subtypes of annotation_occurrence that are within the scope of this effort are annotation_text_occurrence, annotation_curve_occurrence, and annotation_symbol_occurrence. Each has an .item attribute that references the item that is to be styled. In the case of the annotation_text_occurrence, the item is a text_literal_with_extent; in the case of the annotation_curve_occurrence, the item is a polyline; and in the case of the annotation_symbol_occurrence, the item is a defined_symbol.

Additionally, each annotation_occurrence has a .styles attribute that is used to assign that occurrence’s particular style by referencing the presentation_style_assignment entity data type. The presentation_style_assignment lists the required style for that instance of an annotation_occurrence (i.e., text_style for annotation_text_occurrence, curve_style for annotation_curve_occurrence, and symbol_style for annotation_symbol_occurrence).

Figure 1. Styling annotation text

#160=DRAUGHTING_PRE_DEFINED_TEXT_FONT('ISO 3098');
#165=TEXT_LITERAL_WITH_EXTENT(' ','Look at this edge!',#164,'baseline right',.RIGHT.,#160,#600);
#170=TEXT_STYLE_FOR_DEFINED_FONT(#169);
#171=TEXT_STYLE_WITH_BOX_CHARACTERISTICS('a text style',#170,(
 BOX_HEIGHT(1.),BOX_WIDTH(1.),BOX_SLANT_ANGLE(0.),BOX_ROTATE_ANGLE(0.)));
#172=PRESENTATION_STYLE_ASSIGNMENT((#171));
#173=(ANNOTATION_OCCURRENCE()ANNOTATION_TEXT_OCCURRENCE()DRAUGHTING_ANNOTATION_OCCURRENCE()
 GEOMETRIC_REPRESENTATION_ITEM()REPRESENTATION_ITEM(' ')STYLED_ITEM((#172),#165));
#600=PLANAR_EXTENT('extent of text string',60,10);

Complete Part21 example can be found here callouts.stp.

Visual depiction of associativity with leader curve

The associativity between an annotation text and elements of the shape representation can be visually depicted via a leader_curve. A leader_curve is a complex instance with annotation_curve_occurrence, annotation_occurrence, draughting_annotation_occurrence, leader_curve, representation_item, geometric_representation_item and styled_item. The styled_item.item points to the underlying geometry of the leader_curve. At the target end a leader line is terminated by a leader_terminator symbol. Leader_terminator has again a complex instantiation corresponding to the instantiation of leader_curve. The name attribute inherited from styled_item points to a defined_symbol. In the scope of this effort defined_symbol represents an implicit definition of a symbol. Defined_symbol points to a pre_defined_terminator_symbol that gives a description of the symbol and a symbol_target that represents location and orientation of the symbol instance. Pre_defined_terminator_symbol can be instantiated with the names ’blanked arrow’,’blanked box’,’blanked dot’, ’dimension origin’, ’filled arrow’, ’filled box’, ’filled dot’, ’integral symbol’,’open arrow’,’slash’ or ’unfilled arrow’.

Figure 2. Representation of leader curve

#205=(ANNOTATION_CURVE_OCCURRENCE()ANNOTATION_OCCURRENCE()DRAUGHTING_ANNOTATION_OCCURRENCE()
 GEOMETRIC_REPRESENTATION_ITEM()LEADER_CURVE()REPRESENTATION_ITEM(' ')STYLED_ITEM((#300),#250));
#250=POLYLINE('leader curve',(#251,#252,#253));
#300=PRESENTATION_STYLE_ASSIGNMENT((#301));
#400=(ANNOTATION_OCCURRENCE()ANNOTATION_SYMBOL_OCCURRENCE()DRAUGHTING_ANNOTATION_OCCURRENCE()
 GEOMETRIC_REPRESENTATION_ITEM()LEADER_TERMINATOR()REPRESENTATION_ITEM(' ')STYLED_ITEM((#410),#500)TERMINATOR_SYMBOL(#205));
#500=DEFINED_SYMBOL(' ',#510,#514);
#510=PRE_DEFINED_TERMINATOR_SYMBOL('filled arrow');
#514=SYMBOL_TARGET(' ',#511,7.5,2.5);

Complete Part21 example can be found here callouts.stp.

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