By Dennis Collin
When training AutoCAD, creating hatch infill objects is a bane for both new and existing users alike. Reasons for hatching not working can be down to many factors, including non watertight boundaries, incorrect scales, corrupted drawings and also entities drawn with differing ‘Z’ values.
Using the viewcube (in full AutoCAD) or the DDVPOINT command in AutoCAD LT reveals the problems some drawings have when examined in elevation. A good 2D drawing should appear flat. Whereas in the example below, it is more akin to the Highlands of Scotland!
The full version of AutoCAD has a Flatten routine in its Express tools package which changes all z values to zero. However LT doesn’t have any express tools, but by utilising Lisp routines from popular sources. LT’s functionality can be extended and these problem files fixed, without having to locate a colleague who has the full AutoCAD application.
A Lisp file is just a text file of a few kilobytes and once loaded via the Appload function, can be added to the startup suite. AutoCAD can flatten drawings to a flat zero ‘z’ value which will make the creation of hatch, measurement of distances and functions like trim and extend more reliable.
This flatten tool, referred to as Superflatten is an improvement of the flatten tool, supplied with AutoCAD’s Express Tools suite. Similar examples can be found in the links below.
To see how you can load Lisp routines in AutoCAD LT and add them to a start-up suite go here:
To see a selection of popular online Lisp resources, go here:
I will say now whilst most routines are great, there are a few ‘buggy’ examples which may not perform as expected. Therefore, the use of external routines is ‘at your own risk’. As a precaution I will always backup files prior to running a routine. Also run the routine on a testbed setup just in case problems result. Better to be safe than sorry!