Datasheet

3
■ WORKING WITH AUTOCAD 2011 DRAWINGS
Preparing Drawings in CAD or BIM
CAD and BIM programs are primarily vector tools. Software engineers have pro-
grammed intelligence in these programs in the form of numerous parameters that con-
trol the appearance of building components for most conceivable real-world situations.
Modern CAD and BIM programs include a few raster features, such as the ability to
do the following:
A• ssign pixel-based textures to objects and bounded spaces
P• rint or export images directly
A• ccess 3D rendering features that calculate pixels based on geometry, lighting,
and materiality
Photoshop, on the other hand, is primarily a pixel-manipulation tool, with a few
notable exceptions (such as the Pen tool and 3D toolset). When it comes to enhanc-
ing drawings, what we are really talking about is rasterizing, or softening, hard-edged
objects and bounded spaces with pixel-manipulation techniques, which is where
Photoshop truly excels.
Although it’s possible to enhance a single-layer line drawing exported from
CAD or BIM, my preference is to import multilayered drawings so that line thickness
and anti-aliasing can be managed in Photoshop. The ability to transfer multilayered
drawings from CAD or BIM into Photoshop is complicated by fundamental differences
between vector and raster data.
On this book’s accompanying DVD I’ve included a LISP program I wrote to
automate the transfer of drawings from AutoCAD to Photoshop. (LISP is the LISt
Processing interpreted programming language that has been part of AutoCAD for
decades.) Such automation is theoretically possible in other CAD programs, but not
provided in this book.
There is no way to transfer multilayer drawings from Revit Architecture directly
into Photoshop without using AutoCAD as an intermediate step. We therefore need to
enhance single-layer drawings coming directly from Revit (see “Working with Revit
Architecture 2011 Models” later in this chapter).
Working with AutoCAD 2011 Drawings
I’m working with AutoCAD 2011 in this book, but the LISP program and techniques
presented will work in versions of AutoCAD going back more than a decade, to
AutoCAD 2000. There are various steps to working with AutoCAD drawings, which I
cover in detail in this section.
The game plan for transferring any CAD drawing into Photoshop is to first
clean up the CAD drawing you’re interested in enhancing. Cleanup will be necessary
for every drawing you transfer from AutoCAD into Photoshop.
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