Let’s start with some terminology:
- DRAWING FUNCTION – Intended use of the drawing e.g. Roof Plan.
- DATABASE – The source of the information is a DATABASE (file).
- OBJECTS – Drawings consist of graphical OBJECTS represented on a computer screen or printed on paper.
- OBJECT TYPE – 1. PRODUCT-TYPE e.g. Brick Wall 2. GRAPHICAL-TYPE e.g. Line, Arc, Circle.
- RECORD – Each object has a RECORD in the DATABASE.
- PROPERTY – Each RECORD has a list of the PROPERTIES.
- PROPERTY LIST – Names and values of an object’s properties vary according to the type of object.
- PROPERTY TYPE – May be a singular ID (e.g. its layer-name), a switch (e.g. ON/OFF) or a selection LIST (e.g. Color Red, Yellow, Green).
- PROPERTY NAMES – e.g. Color, linetype, layername.
- PROPERTY VALUE – e.g. Red, dashed, WAL37-200P02
- Property VALUES are assigned to an object in one of three ways: 1. by the the system as the object is drawn, 2. by individual change, 3. from a PROPERTY LIST.
- LAYERNAME – Name of the object’s a PROPERTY LIST.
- LAYER – A group of objects with same LAYERNAME,
- LAYER-STATE – A named record of the display and edit condition of a group of layers. e.g. “Roof-Plan”.
Key aspects of a drawing database:
- Drawing OBJECTS
- Object PROPERTIES
- Symbol Tables
- LAYERS
- BLOCK Definitions and References
- Layout and Paper Space Information
- Named Object Dictionaries
- Dimension and Annotation Systems
- Display and Visibility Controls
- External References (Xrefs)
- System Variables and Drawing Settings
- Relationships Between Database Elements
OBJECT types:
- Lines
- Polylines
- Arcs
- Circles
- Splines
- Ellipses
- Hatches
- Text and MText
- Dimensions
- Leaders
- Tables
- Blocks (inserted references)
- 3D solids
- Surfaces
- Meshes
- Point objects
Entries in an object record:
- A unique object ID (handle)
- A type definition
- Geometric data
- Object properties
- Relationships to other database objects
A record of a line consists of:
- Drawing space (paper or model)
- Layer name
- Start point coordinates
- End point coordinates
- Colour
- Linetype
- Line-type scale
- Lineweight
- Transparency
- Plot style information?
First let’s get the terminology right.
Alias. An AutoCAD short version of a command name e.g. ML= Make Line has same effect as typing the full command name LINE on the Commandline.
Shortcut. (keyboard) A combination of keys such as Ctrl+chr when pressed together either at the command prompt or mid-command inputs a command string to the commandline e.g. Ctrl+E might issue the command “END <enter>” .
Function Key. Such as F8 that switches the drawing environment between orthographic or non-orthographic drawing.
Generic Autocad command. A standard command supplied by the program.
Custom command. An add-on custom command supplied by third-party software add-on such as MycadHELPER may have a long name or Alias.
Lisp function. A command or sub-function that can only be executed by entering a lisp expression at the command prompt. MycadKEYS provides 900 of these.