This month we are looking at the DDChprop / Change commands.  This is one of the most basic of the AuoCAD commands, but it is also essential to the CAD operator as an editing tool.

The DDChprop and the Change commands will enable you to change all entities in a drawing, either one at a time or in selection sets.   These are the most frequently used editing commands because they modify the properties of all objects.  DDChprop changes an entities properties, including color, linetype, thickness and layer.  The Change command is capable of the making the same changes but can also move end points and make alterations to circles, text, blocks, attributes and change the elevations of entities.  These property list look very much like those found in the DDlmodes with the exception that DDChprop has the ability to edit the linetype scale and the thickness of a 3D object.  Using the DDChprop and Change is a quick and easy way to edit existing entities.  After typing DDChprop at the command prompt, AutoCAD will ask you to select the entities that you want to edit, then it will display a dialogue box with the entities properties that you can change.  From this dialogue box you can select the color, layer or linetype buttons.  Each of these selections will display a flyout that contain a list of properties from which you can select

ELEVATIONS / THICKNESS

In a 3D drawing you can assign an elevation and a thickness to an entity.  The Change command will allow you to change the position of a 2D objects position in a 3D space by changing the objects elevation above the X-Y plane.  A value that is positive will adjust the object in a positive Z direction.  A negative value will adjust the object in a negative Z direction.   The Thickness of a 3D object is the extruded distance of the object.  Using the Change command, again a positive value applied to an objects thickness will extend the object in a positive Z plane as will a negative input extend the selected object in a negative Z plane.

LAYERS

Changing layers from the Change Properties dialogue box will allow you to select several objects and place them on a single layer.   Invoke the DDChprop from the command line and select several entities on different layers.  When the dialogue box comes up, you can select a new layer from the list of available layers in the current drawing.  When an entity moves to another layer, and if you have linetypes and colors set to bylayer, the selected entities will take on the properties of the current layer.  However, you can over ride this by clicking on the linetype button and changing the lintype of the selected objects.  The same will be for the colors of the selection set, if you change the color of the objects, regardless of the bylayer color; the entities will take on the newly selected color.

LINETYPES / LTSCALE

Just as you can change the layer(s) of selected objects, you can change the linetype of selected objects.  Using the DDChprop command, and selecting objects that you wish to edit then clicking on the linetype button, you can then choose a new linetype.  By doing this, if you are drawing entities bylayer, the objects will loose their bylayer property and accept the newly selected linetypes current properties.  If you change a linetype to a broken type line such as a center or dashed line and you see that the linetypes current scale does not allow you to see line breaks, you can change the line scale.  To do this you simply change the value in the linetype scale field.

COLORS

Using the same DDChprop command will allow you to edit the colors of the selected objects.   You can change the color to be independent of the layer or you can change the color, and linetype for that matter, by changing the entities to a layer that has the color properties that you need.  All principles earlier described apply.

CHANGING END AND INSERTION POINTS TEXT AND CIRCLES

The Change command will have impact on three other types of entities.  Circles, Text and Blocks.  Although there are several other ways you can edit these entities, some of them are even faster, you can call on this as a base command in an AutoLISP routine that will allow a programmer to have many functions available in one routine.  Changing a circle can be done in two different fashions.  After typing Change at the command prompt, hit the enter key twice then you can enter in a new radius, or you can place the cursor in a position outside or inside of the selected circle and the circle will snap to that position.  Changing all aspects of editing text can be achieved using the Change command.  By invoking the Change command then selecting a text object, continue touching the enter key until you reach the property of the text object that need to edit, then edit it.   When selecting a block you can edit only two properties.  The first is the insertion point and the second is the rotation.  If you use the DDChprop editor on a block you can edit the blocks layer, linetype and color.  This will only affect entities in the block that are drawn on layer zero.