BASE DIR AND GENERALIST

https://valvearchive.com/archive/Half-Life/Half-Life%202/Other/SOURCE_InfoSheet.pdf
https://www.4gamer.net/shots/hl2/hl2.html
https://www.hlportal.de/?site=image&do=showimage&cat_id=128&image_id=1518
https://www.gamespot.com/articles/the-final-hours-of-half-life-2/1100-6112889/
https://valvearchive.com/archive/Other%20Files/Publications/FPS.pdf
https://valvearchive.com/archive/Other%20Files/Publications/AI in First-Person Shooter Games.pdf
https://www.hl-inside.ru/gallery/shots/?page=1
https://www.valvetime.co.uk/threads/early-half-life-2-screenshots-from-retro-gamers-article.257805/

SPECIFIC SCREENSHOTS -- 

HAMMER EDITOR

canals.png: https://valvearchive.com/archive/Other%20Files/Publications/GDC2004_Half-Life2_Shading.pdf