The most important must-read document for the MacDOOM level designer is the "Unofficial DOOM Specifications" by Matt Fell. It contains a plethora of detailed information on all aspects of how DOOM works.
Less comprehensive, but more readable information is presented in a Q&A format in the "DOOM Level Design FAQ" (Frequently Asked Questions), edited by Tom Neff. This document can save many hours of hair-pulling when that level you've worked on for days doesn't do what you intended.
Other useful information can be found in "DOOM Metrics" by Scott Amspoker, which contains information on relating 'DOOM size units' to 'real-world' sizes. Also the file "Managing Textures and the Unpegged Attribute", again by Scott Amspoker, gives a good overview on how to use textures effectively.
To obtain these documents and others, try my World-Wide-Web site at
<http://www.ozemail.com.au/~pmd/peps.html>
Alternatively, these files can be obtained from
<ftp://ftp.cdrom.com/pub/idgames/docs/editing>
as the following files:
dmspec16.txt - The Unofficial DOOM Specs, version 1.666
design12.txt - The DOOM Level Design FAQ, version 1.2
metrics.zip - DOOM Metrics
textures.zip - Managing Textures and the Unpegged Attribute
Many other documents are also available on the internet - try using your favourite Web searcher to find more information.
