Games · Pro
Physically-Based Ray Tracer
A from-scratch path tracer that renders photoreal scenes with global illumination, materials, and a BVH acceleration structure on multiple threads
You build a Monte Carlo path tracer from scratch that simulates how light physically bounces through a 3D scene to produce photorealistic images. The renderer handles diffuse, metallic, and dielectric materials, constructs a bounding volume hierarchy for fast ray-triangle intersection, and distributes work across CPU threads for practical render times. This is one of the most direct ways to understand the math that drives every modern game engine and offline renderer.
What you build
- Casts primary rays through a configurable pinhole camera with anti-aliasing via multi-sample averaging
- Recursively traces indirect light bounces using Monte Carlo sampling to produce soft shadows and color bleeding
- Supports Lambertian diffuse, metallic mirror, and dielectric glass material types via a PBR BRDF model
- Builds a bounding volume hierarchy (BVH) over the scene geometry to reduce intersection cost from O(n) to O(log n)
- Renders on multiple threads using data-parallel tile dispatch, cutting wall-clock time proportional to core count
- Outputs a PPM or PNG image file that can be inspected after every test render
- Reports per-render statistics including samples per pixel, ray count, and elapsed time
What it teaches
- Monte Carlo integration and how variance decreases with sample count
- Ray-object intersection mathematics for spheres, planes, and AABB volumes
- BVH construction and traversal as a fundamental scene acceleration structure
- PBR material models including the Cook-Torrance BRDF and Fresnel reflectance
- Data-parallel CPU programming and task decomposition across threads
- Floating-point precision pitfalls like shadow acne and how to handle them with ray offsets
How it works
- 1
Camera
- Generate primary ray
- Per-pixel, multi-sample
- 2
BVH Traversal
- Test ray vs AABB hierarchy
- Descend to leaf geometry
- 3
Intersection
- Sphere / triangle hit test
- Record t, normal, material
- 4
Material Scatter
- Sample BRDF direction
- Attenuate throughput
- 5
Accumulate
- Recurse or return emittance
- Average samples to pixel
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Take it further
- Add a triangle mesh loader (OBJ format) and render a full low-poly model with smooth normals interpolated across faces.
- Implement importance sampling of a physical area light source to reduce noise at equal sample counts compared to uniform hemisphere sampling.
- Add a thin-lens camera model with configurable aperture and focal distance to produce depth-of-field blur.
