CAD Hatch Defaults

Hatches are a collection of lines which fill an area in a pattern.  This is unlike fill styles where the area is filled with different coloured pixels.  When selecting hatch styles, the dialog box shown to the right will be displayed.

The Patterns list shows which patterns are available.  The first pattern is called <User Defined> and allows you to define a simple pattern of angled lines with one or more spacings.  The remaining patterns are predefined and allow for the representation of such things as concrete or earth.  These patterns have been imported from AutoCAD.  As you highlight a pattern, the preview window will show you what the pattern looks like when applied to a sample of graphical elements.

Hatch Defaults

The user defined hatch is a series of lines at any given angle which is specified in the Angle field.  The angle follows the polar convention.  An angle of 45° would create lines going from southwest to northeast whilst an angle of -45° would create lines from northwest to southeast.  The Spacings list defines the spacings of the lines and the Add and Remove buttons allow you to add and remove spacings from this list.

If you select a hatch pattern other than the user defined, the Spacings list and Angle field will disappear and a Scale field will become visible.  The value in this field is used to scale the predefined hatch pattern.

It is often the case that the complete polygon to be hatched is not available.  This happens when a building face is on the edge of a survey and the full building footprint has not been surveyed.  In these cases, there are options to hatch to one side of an element.  The value in the Offset field is used for such hatches and defines the depth of hatch that you wish to create.

There are also options to “burn” text into a hatch object.  The Surround field allows you to specify the depth of the required space around the text.

The Hatch Mode

The Hatch Mode field defines how the elements to be hatched are interpreted.  There are three options and for each option, the intersections of each line in the hatch pattern with the elements to be hatched are calculated.  They are then used as follows.

• Normal: The hatch lines will be turned on at the first intersection, off at the second, on at the third and so on.

•  Outer: The hatch lines will be turned on at the first intersection and off at the second.  If there are four points or more, the hatch lines will be turned on at the penultimate point and off at the last.

•  Ignore: The hatch lines will be turned on at the first intersection and off at the last.

Normal Hatch Mode

Outer Hatch Mode

Ignore Hatch Mode