Source

Renderer

• Version 2.0 (and below) shaders, bump mapping, LOD on models and world
• Author shaders with HLSL
• Cube and environment mapping
• Dynamic lights, vertex lighting and light maps, many light types including flickering, pulsing etc.
• HDR lighting
• Water with refraction and fresnel effects
• Advanced particle system that can emit sprites or models
• Projected shadows allow for a large number of characters per scene
• Occluder entities for visibility blocking
• Indoor/Outdoor environments
  • Deformable terrain
  • 3D skyboxes extend the horizon and add parallax on distant objects
  • Dynamically rendered organics (grass, trees etc)
• Subdivision surfaces, diffuse & specular bump maps
• Real-time radiosity lighting
• Effects include but are not limited to: particles, beams, volumetric smoke, sparks, blood, environmental effects like fog and rain
• Scalability
  • DX6-DX9 hardware supported

Materials System

• Instead of traditional textures, Source defines sets of materials that specify what the object is made from and the texture used for that object. A material specifies how an object will fracture when broken, what it will sound like when broken or dragged across another surface, and what that object's mass and buoyancy are. This system is much more flexible than other texture only based systems.
• Materials can interact with objects or NPCs such as mud or ice for vehicles to slide/lose traction on.

Multiplayer Network Code

• Time and gamer tested by millions of gamers around the world
• Support for both LAN based multiplayer and Internet based multiplayer games
• Prediction analysis for interpolating collision/hit detection
• Optimizations for high-latency, high-packet loss 56k connections

Advanced Characters

• Detailed and believable characters
• Realistic eyes
  • Focus on player/object, not simply parallel views
  • Proper eye bulge for realistic eye reflections
• Simulated musculature provides outstanding emotions, speech and body language
• Language independent speech, characters can naturally speak in many languages
• Skeletal/bone system for animation
• Layered animation system can synthesize complex animations out of several pieces

Physics

• More responsive world with realistic interactions
• Sounds & graphics follow from physics
• AI characters can interact with physically simulated objects
• Ropes/cables, machines, constraint systems, ragdoll physics
• Can be controlled by level design
• Kinematic animated bone followers
• Custom procedural physics controllers
• Vehicles
  • Wheels slip and skid
  • Realistic suspensions with springs on each wheel
  • Realistic leaning during acceleration/deceleration and turning
  • Individually tunable parameters such as horsepower, gearing, max speed, shift speed, tire material, tire friction, spring tension/dampening etc.
  • Multiple players in a vehicle in multiplayer
  • Hovercraft support for cheaper simulation

Advanced AI

• I/O system allowing level designers to control AI
• Sophisticated navigation: characters that run, fly, jump, crouch, climb stairs and ladders, and burrow underground
• AI senses things using sight, sound, smell
• AI relationships determine friend/foe status of other entities
• Battle AI allows squads of AI characters to operate together, know when to advance, retreat, lay cover fire, etc.

Sound System

• 7.1, 5.1 surround sound, 4 speaker surround
• High-quality 3D spatialization
• Custom software DSP
• Automatic DSP based on environmental geometry
• ADPCM decompression
• 16-bit 44KHz, stereo wave data with all features
• MP3 decompression (requires Miles license)
• Support for audio streaming on any wave
• Real-time wave file stitching
• Pre-authored Doppler effect encoded waves
• Pre-authored distance variant encoded waves
• Commentary system

UI

• Server browser - Displays all active game servers and allows a player to choose which one to participate on. Players can filter and sort server lists in order to speed up the display and selection of a server.
• Friends instant messenger - (Undergoing Maintenance) Allows players to message each other both in and out of the game as well as join friends in existing games. No more confusion about what server your friends are on, you can easily join with this feature.
• VGUI - Valve's custom GUI interface mimics most of the Windows controls but is rendered using the Source engine for both in game and out of game uniform UI display. Some features:
  • Dynamic in-game HUD display
  • Many widgets/controls (i.e. buttons, treeview, html control, ...)
  • Themes/custom visualisation allowed
  • Platform independent
  • Localized texts (Unicode compliant)

Programming

• All code written in C/C++ using Visual Studio 6.0. Easily and quickly derive new entities from existing base classes.
• Internal context sensitive performance monitoring system.
• Graphics performance measurement tools built into the engine.
• Modular code design (via DLLs) allows swapping out of core components for easy upgrading or code replacement.
• DX9 shaders all written in HLSL.

Tools

• Face Poser
  • Facial expression tool used to craft speech and emotions
• Valve Hammer Editor
  • WYSIWYG World editor
  • Create world brushes
  • Terrain editor
  • Place detailed world models and AI NPCs
  • Set navigation points/paths for NPCs
  • Place triggers, clip brushes, logic etc.
  • Allows level designer to hook up I/O between entities to control AI within the game
• Half-Life Model Viewer
  • Full model previewer
  • Rotate models in any direction
  • Setup hit boxes
  • View physics hull
  • View normals
  • Wireframe, shaded or textured view modes
• Studiomdl
  • Model compiler
• Vbsp, Vrad, Vvis, VMPI
  • Map compilation tools (bsp, lighting and visibility)
  • VMPI - distributed compilation tool allowing level compiles to be spread across many PCs greatly reducing compile times
• Exporters
  • XSI, Max and Maya .smd exporters for exporting 3D models