CPUEngine

A real-time 3D graphics engine that runs entirely on the CPU — no GPU required.

Built to learn computer graphics at the lowest possible level, then push performance as far as it can go using modern SIMD vectorization (AVX2/FMA on x86, NEON on ARM).

Features

Rendering

• Software rasterizer with perspective-correct interpolation
• Z-buffer depth testing
• Frustum culling (bounding sphere)
• Wireframe and solid rendering modes
• Runtime render resolution scaling (270–1080) with nearest-neighbor upscale
• Thread pool for parallel triangle rasterization

Shading

• Flat shading
• Gouraud shading with per-vertex lighting
• Specular highlights (Blinn-Phong)
• Procedural shaders (stone, wood, plane/checkerboard)
• Dynamic point lights

Post-Processing

• SSAO (screen-space ambient occlusion) — multi-radius sampling, single-pass fused compute+apply
• Depth fog (distance-based atmospheric fog)
• Light fog (volumetric light scattering)
• Edge-detect anti-aliasing (FXAA-style)

Engine

• OBJ model loading with TGA textures
• Scene file format for placing models
• First-person camera with configurable FOV and clip distances
• In-engine settings menu (render, camera, fog controls)
• HUD overlay with FPS and position readout
• SIMD and scalar code paths (build with -DSIMD=ON or -DSIMD=OFF)

Building

Requires SDL2 and CMake.

mkdir build && cd build

# SIMD enabled (recommended)
cmake -DSIMD=ON .. && make -j$(nproc)

# Scalar fallback
cmake -DSIMD=OFF .. && make -j$(nproc)

On macOS, use sysctl -n hw.ncpu instead of nproc.

References

• 3D Math Primer for Graphics and Game Development, 2nd Edition
• Mathematics for 3D Game Programming and Computer Graphics, 3rd Edition
• Eric Zhang — Graphics Blog
• ssloy — tinyrenderer
• Fabian Giesen — Software Occlusion Culling
• Karl Techno — Software Rasterizer

TODO

Rendering

• Shadow mapping
• Normal mapping
• Texture filtering (bilinear / mipmaps)
• Occlusion culling
• LOD (level of detail) mesh switching

Physics Engine

• Rigid body dynamics (position, velocity, acceleration integration)
• Collision detection — broad phase (spatial hashing or BVH)
• Collision detection — narrow phase (GJK / SAT)
• Collision response (impulse-based resolution, restitution, friction)
• AABB and OBB bounding volumes
• Gravity and constant force fields
• Constraint solver (contact constraints, joint constraints)
• Spatial partitioning for scalable object counts
• Raycasting (for picking, line-of-sight, projectiles)
• Static vs. dynamic body types (infinite mass statics)
• Sleep / deactivation for resting bodies

Engine

• Scene graph / transform hierarchy
• Entity-component system
• Audio
• Scripting / hot-reload