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Half-Life 2 and Source. Presented by Jay Stelly. Tech lead decisions. Design a better structure for code development Investments in scripting Improve iterative creative processes Investments in distributed computing Investments in optimization. Code development. Larger group of engineers - PowerPoint PPT Presentation
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Half-Life 2 and SourcePresented by Jay Stelly
Tech lead decisions
Design a better structure for code development
Investments in scripting Improve iterative creative processes Investments in distributed computing Investments in optimization
Code development
Larger group of engineers Larger code base Lots of dependency System coding vs. leaf coding Lots of new technology, new interactions
Code development solutions
Reduce scope of programming decisions Dynamic linking
• Binary compatibility through interfaces• Similar to COM in theory, lighter weight in practice• Versioning system• Lots of changes behind layers• Build & deploy only changed components
One file leaf coding• Auto-registration systems• Systematic approaches to behavior, serialization,
networking, hooks
Code development solutions
Faster compiles• DLLs are smaller• Reduced dependencies• Use incredibuild distributed to 12 machines
• 4:1 - 8:1 improvement in most cases• Use VMPI• Many leaf coders use edit & continue• Console variables
Example: Shaders
Graphics API isolated in a component (Shaderapi.dll)• Reduced dependency on dx9• Moved from dx8 to dx9 with almost no code changes outside this
layer Materials system isolated in a component
• Allows mod authors to plug-in HLSL code• Leaf code uses material abstraction
Lots of custom shaders needed for speed• Unrolled into light/bone/state combinations• Used perl scripts to automate this metaprogramming• Write one, generate thousands• Use VMPI to distribute compilation of shaders• Incremental loading system
• fast iteration by a single developer
Investments in scripting
General scripting languages failed for us• Shader language• AI behavior language• Animation description language (shipped)
Simple hierarchical text blocks• Simple• Easy to parse• Extensible• No conditionals, no state• Tools that operate on all scripts• Maps, soundscapes, materials, surfaceproperties, scenes,
ragdolls, game_sounds, etc.
Improve iterative creative processes
Reduce scope of creative work• Decrease cost of iterations• Improve quality of iterations• Dynamic linking• Symbolic linking
Add layers of abstraction• Architect around workflow
Re-examined core production processes• Level design• Animation• Localization• Audio
Allow creative people to iterate in isolation• Also in parallel
Example: Level design
Symbolic links to audio, scenes, animations, code Some embedded structures remain
• Prefabs• templates
Entity I/O• Visual scripting language• Connect named inputs to outputs• Symbolic link to code• Extensible and backwards compatible• Create specialized inputs & outputs as needed
Example: Level design (continued)
Response system• Contextual symbolic links• Entity I/O can trigger concept• Set of contextual choices results in symbolic link
• Example: male/female speech• Chooses an appropriate thing to say given the character and
the current game context Shaders instead of textures
• Symbolic link to rendering code• Symbolic link to proxy code
• Procedurally modify shader variables• Symbolic link to actual textures
Example: Animation
Symbolic link to animation• Can also be a blended set• Serialization uses symbols• Named blend parameters• Models share animation, can override by name
Symbolic links to bones• Add new bones to specific animations & characters• Share animation among models• Named attachments for code & levels• Named skeleton merges for models• Dynamically linked
Example: Animation (continued)
A composite model for animation• N-way blend matrix• Partial skeleton animations
• Gestures• Facial animation + procedural eye movement• Lip sync• IK
All are independent layers Author characteristic gestures & postures for characters
• Build tons of higher-level animations out of these building blocks
Shipped ~3 hours of scenes in HL2 vs. ~10 minutes in HL1
Example: Scenes
Symbolic link to marks, objects, characters• Independently editable in the level
Link to AI commands• MoveTo, FaceTo, LookAt
Interactive with player Link to animations, gestures, speech
• Change gesture timing per-instance Animation system builds composite from all of
the above
Example: Audio
Game_sounds.txt• Simple config file for each sound effect
• Allows single wave or set of random waves• Edit parameters (volume, attenuation, voice stealing, pitch shift, etc) per
wave file Soundscapes.txt
• Position-based environmental sound• Also controls mixing
Soundmixers.txt• Classifies sound effects into groups across entire game• Named mixes of sound groups that can be linked into soundscapes
Dsp_presets.txt• DSP effect parameters, parametric algorithms• Automatic DSP tuning parameters
Example: Audio (continued)
Surfaceproperties.txt• Primarily for physics properties • Physically based sounds
• Impacts• scrapes• footsteps
• Audio reflectance properties• Audio hardness/softness for modifying physically
based sounds• Symbolic links to actual sounds
Distributed computing
Half-Life used SMP/threaded systems for offline pre-processing Source uses distributed systems instead (VMPI)
• Scales higher• Cheaper• Better long-term (keep old machines)• Good for high latency jobs
Incredibuild VMPI
• Radiosity, hours in Half-Life, minutes in HL2• Visibilty• Shader re-compile• Scales to 32 machines
Upgraded to 1Gb/s network Use idle workstations as slaves
Optimization
Lots of future work Memory bound more often than instruction
bound• Much easier for leaf coders to get memory bound
Otherwise fill bound, or I/O bound usually
Summary
Isolate creative tasks, remove dependencies Some architecture should be based on workflow
& personnel Programming in C++, scripting with simple text
configuration files Faster, higher quality iteration through focus,
isolation, dynamic linking, reduced dependency, reduced compilation steps
Can use a larger team in a more parallel fashion