IAppSystem Derived Systems
- IVGui - Interface to core vgui components
- IStudioRender - Studio Render interface
- IStudioDataCache - Responsible for caching studio render data (models, etc.)
- IMaterialSystem - Responsible for managing and rendering materials and their components including shaders and textures. Can be thought of as essentially a DirectX wrapper that also handles texture and shader loading.
- ISoundEmmiterSystemBase - Base class for sound emitter system handling
- ICVar - DLL interface for ConVars and ConCommands.
- IFileSystem - Provides file loading and parsing functions
- ISurface - Wraps contextless windows system functions