C4 Engine

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The C4 Engine is a proprietary game engine developed by Terathon Software, led by Eric Lengyel. It lets you create 3D games and interactive simulations for PlayStation 5, PlayStation 4, PlayStation 3, Windows, Mac OS X, Linux, and iOS. The latest stable release is version 7.2, released on September 3, 2024.

How it’s built
The engine uses a layered architecture. Lower layers talk to the hardware and operating system, while higher layers provide platform–independent services to game code. While much of the work is focused on 3D graphics, C4 also handles audio, networking, physics, input, and scripting.

Graphics and rendering
C4 is based on OpenGL on supported platforms and uses a forward rendering approach that processes one light at a time. It supports different light sources and shadow styles, including shadow mapping and a variant of cascaded shadow mapping for large outdoor scenes. Shaders can be created in two ways, both shielding the user from the underlying graphics code. You can describe materials with attributes like diffuse and specular colors and textures, and the engine will generate the shader code automatically. A Shader Editor is available for creating more complex materials, giving advanced users greater control.

Terrain and detail
Terrain uses voxel technology, allowing true 3D sculpting with features like overhangs and vertical cliffs. Voxel data is turned into triangle meshes with the Marching Cubes algorithm, and the Transvoxel technique helps stitch areas of different detail levels smoothly.

Special effects and post-processing
The engine can render a wide range of effects, including particles, procedural fire, electrical effects, volumetric fog, and weather. After the main render pass, it can apply full-scene motion blur, glow, and distortion. It does not include tools for creating custom post-processing effects.

Audio and networking
C4 handles WAV audio (16-bit mono or stereo) from memory or disk. A built-in mixer supports frequency shifting, Doppler effects, reverberation, and atmospheric absorption. Multiplayer uses a two-layer UDP-based messaging system. The engine also includes a native physics engine, with the option to integrate a third-party physics solution.

Tools and workflow
The engine ships with core development tools as plug-in modules. The World Editor is the main content creator for buildings, lights, sounds, triggers, and effects. It can import scenes from OpenGEX and COLLADA, enabling work with content from software like Autodesk Maya and 3ds Max. A graphical script editor lets level designers and programmers build logic with a node-like graph, supporting loops and conditional execution. The World Editor also includes a panel editor for creating interactive 2D UI panels that appear inside the 3D world. Panels are dynamic and can include animation and interaction, with mutators to animate panel items. Scripts can be attached to interactive items to trigger actions when players interact with them.

Licensing and education
C4 Engine is licensed to individuals for $100, with all future updates included. It has seen adoption in universities and research projects, including MIT, Georgia Tech, Worcester Polytechnic Institute (WPI), McMaster University, and the University of Kempten. Students often use it for game projects, and some work has been showcased in festivals and media.