creator Valve Software has released a major update to its Source SDK, which allows hobbyists and other interested parties to create content in the company's Source engine.
The updated SDK, which is available now over Valve's Steam content delivery system, includes several major new features and fixes for the tools in the Source SDK.
In particular, High Dynamic Range lighting, which was used for the first time in Valve's Half-Life 2: Lost Coast
add-on, is now supported in the tools, as is game Day of Defeat: Source
In addition, new Hammer Editor features for Valve's map editor include a VGUI Model browser with real-time 3D view, map autosave/backup, and model and displacement rendering in 2D views.
More information on both the SDK and the updates to it are available at Valve's Source SDK release notes
on the company's Developer Wiki.