Mar 13
AutoCAD Entity Database Revealed Absolutely the most powerful use of AutoLSIP is the ability to access and manipulate the entity drawing database. Database is the term that represents the contents (entities or objects) of the AutoCAD drawing file. An AutoCAD drawing is made up of “Entities,” or as they are also referred to as...
Read MoreMar 16
When a drawing is opened for editing, a unique “name” is given to each object in the entire drawing. This “Entity Name” is actually a pointer into a file which holds the information necessary to draw the entity on the screen or on a plotter. As an example of this, draw a line from 0,0 to 2,2 on the AutoCAD layer “0″: Command:...
Read MoreMar 26
The (entget) function returns an association list containing the database record which defines the object in detail. This applies to graphical and non-graphical entities. Items from within the association list can be extracted using the ASSOC function. Items within the list are assigned AutoCAD DXF group codes for each part of the entity data. The DXF group codes...
Read MoreMar 26
First, add a Line into the drawing, then to see the database record for the line object that was just added, type the following at the AutoCAD Command prompt: Command: (setq ELIST (entget (entlast)) <Enter> ((-1 . <Entity name: 7ef031a8>) (0 . “LINE”) (330 . <Entity name: 7ef01cf8>) (5 . “E5″) (100 ....
Read MoreJun 09
During an AutoCAD session each editing command issues a “Select objects:” prompt. At this point the user selects the drawing objects and a selection set is created. A selection set is a group of objects which are stored in an indexed list by their entity name. Each entity name is accessed by pointing to its relative index number in the selection set. The...
Read MoreJun 10
AutoLISP SSGET Function-Relational Tests The FILTER-LIST argument provides access to specific entity properties, such as text height values or block scaling factors. For other numerical relationships (integers, reals, points, and vectors) the -4 group code specifies a relational operator for these numerical conditions. The value of a -4 group is a string indicating...
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