Source 2006
The 
Source 2006 engine branch, also known as the Episode One engine branch, and the last Old Engine branch, was first released in 2006 with 
Half-Life 2: Episode One and 
Half-Life Deathmatch: Source, with previous multiplayer games (
, 
, and 
) also upgraded to the Source 2006 engine. It was distributed in "base source engine 2.gcf." It was obsoleted by the Source 2007 (also known as Orange Box) branch. It requires Half-Life 2 content to operate.
The SDK and SDK Base game for this branch are free to all Steam users.
Features
New since 
Source 2004:
- High Dynamic Range rendering
- A simulation of brightness values outside computer monitors' actual range, and of aperture adjustment.
- Phong materials
- Diffuse reflections for skin and other roughened surfaces on models.
- Facial animation upgrades
- More detail and intenser shapes for close-up performances.
- Dynamic interactions
- Dynamic interactions between NPCs using special animations.
- Lightwarp textures
- 1D textures that tint a material per-texel depending on their brightness.
- DirectX 9 Shader Model 3 (dxlevel 95)
- Unlocks greatly improved shader performance.
- Detail prop shapes
- Improved detail sprites that sway in the breeze and bend away from nearby players.
Availability and Games that uses the Source 2006 branch
Gamecode for the 2006 branch is included in the now-deprecated Source SDK app. Most Valve games introduced with Source 2006 and previous titles that are upgraded from Source 2004 to Source 2006 are now currently using Source 2013 Singleplayer or Source 2013 Multiplayer.
Here are the games that currently runs on Source 2006, or previously runs on prior to it being upgraded to newer branches:
Valve
- 2004 Counter-Strike: Source (Upgraded from Source 2004, Formerly) - Now uses Source 2013 Multiplayer.
- 2004 Half-Life 2: Deathmatch (Upgraded from Source 2004, Formerly) - Now uses Source 2013 Multiplayer.
- 2004 Day of Defeat: Source (Upgraded from Source 2004, Formerly) - Now uses Source 2013 Multiplayer.
- 2006 Source SDK Base 2006
- 2006 Half-Life 2: Episode One (Formerly) - Now uses Source 2013 Singleplayer.
- 2006 Half-Life Deathmatch: Source (Formerly) - Now uses Source 2013 Multiplayer.
Third-Party
- 2006
The Ship: Murder Party and The Ship: Single Player - 2006
Dark Messiah of Might and Magic - 2006
Garry's Mod (Formerly) - Now uses custom version of Source 2013. - 2007
Eternal Silence - 2007
Fortress Forever - 2007
INSURGENCY: Modern Infantry Combat - 2007 Iron Grip: The Oppression[confirm]
- 2009
NEOTOKYO°