"Heidi" is the graphics engine used for video and hardcopy output from AutoCAD. It is Autodesk’s high-speed graphics solution - an "immediate mode" interface designed for the drawing portion of graphics software construction activity. It is the critical core component that coordinates many aspects of 3D graphics application development.
The Heidi Device Interface, HDI, provides a complete environment for creating drivers for hardcopy output from graphics software. It is the same interface first introduced with the AutoCAD 2000 plotting enhancements and it remains the enabling technology graphics in the latest AutoCAD 2008 release."
Windows system printer drives are
generic. They must work with many applications, broadly speaking from "Notepad" via spreadsheets to graphics software. But when it comes to large format CAD files, there are a lot of common and well known problems. Sometimes they do not report the actual printable page size correctly and often they have
problems in interaction with the CAD software.
There are a number of reasons/advantages from going with an optimized plotter driver for AutoCAD over the system printer drivers - one is
quality but there is also performance considerations:
 | SCP-HDI-drivers produce less data compared to plain system drivers, resulting in higher speed
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| SCP-HDI-drivers don't run out of device memory like most plain system drivers
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| SCP-HDI-drivers do a better job of handling drawings with large amounts of raster
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| SCP-HDI-drivers offer better plot quality and speed for CAD drawings than plain system drivers |
