go-progressive-raytracer

Go Progressive Raytracer

A high-performance progressive raytracer written in Go that renders photorealistic images with support for multiple materials, lighting, and complex geometries.

Built following the excellent Ray Tracing in One Weekend series with additional techniques from Physically Based Rendering: From Theory to Practice.

Features

• Progressive Rendering: Samples are added progressively, so renders improve progressively
• Multiple Integrators: Choose between traditional path tracing or bidirectional path tracing (BDPT) for different lighting scenarios
• Rich Materials: Lambertian, metal, glass, dielectric, and emissive materials
• Complex Geometry: Spheres, planes, triangle meshes, and PLY file support
• Advanced Lighting: Area lights, environment lighting, and physically-based illumination
• BVH Acceleration: Optimized ray-triangle intersection for complex scenes

Progressive Rendering

Watch how the image quality improves with more samples per pixel:

1 Sample	8 Samples	64 Samples	512 Samples	4096 Samples
136ms	911ms	6.1s	51s	7m20s

Progressive rendering allows you to see results immediately and stop when quality is sufficient for your needs.

Multiple Integrators: Path Tracing vs BDPT

The raytracer supports two rendering integrators, each with different strengths:

• Path Tracing is the standard unidirectional approach, with paths traced from the camera to the scene, with both direct and indirect lighting sampled at each point - fast and efficient for most scenes with direct lighting and diffuse materials.

• BDPT traces paths from both the camera and light sources, connecting them to explore more light transport paths. This produces significantly better results for images with more complex lighting (e.g. specular reflections, caustics, complex indirect lighting)

BDPT vs PT Comparison:

Path Tracing	Bidirectional Path Tracing (BDPT)
256 samples • 12.8s	64 samples • 12.8s

The comparison above (cornell-boxes scene) shows equal wall-clock rendering time (~12.8 seconds). Despite using 4x fewer samples, BDPT produces comparable or better quality, especially in the reflected light on the ceiling where path tracing shows more noise.

Sample Renders

Dragon Mesh

Dragon PLY mesh with 1.8 million triangles demonstrating BVH performance
Model by Bernhard Vogl via PBRT scenes
512 samples • 7m22s render time

Default Scene

Spheres with various materials (metal, glass, lambertian) on a ground plane
4096 samples • 1m37s render time

Cornell Box

Cornell box with rotated boxes, area lighting, and realistic materials
4096 samples • 7m20s render time

Sphere Grid

Grid of metallic spheres showcasing BVH acceleration and parallel rendering
1024 samples • 7m27s render time

Triangle Mesh

Complex triangle mesh geometry with procedurally generated shapes
1024 samples • 1m37s render time

Quick Start

Prerequisites

• Go 1.24.3 or later

Command Line Interface

# Clone the repository
git clone https://github.com/df07/go-progressive-raytracer.git
cd go-progressive-raytracer

# Build the executable
go build -o raytracer.exe main.go

# Render a scene
./raytracer.exe --scene=default --mode=progressive --max-passes=5

Web Interface

The web interface provides real-time progressive rendering with live updates:

# Start the web server
cd web
go build -o web-server.exe main.go
./web-server.exe -port 8080

# Open http://localhost:8080 in your browser

Web Features:

• Real-time streaming: Watch renders improve live via Server-Sent Events
• Interactive controls: Adjust scene parameters, resolution, and quality
• Multiple scenes: Switch between all available scenes
• Live statistics: Monitor rendering progress and performance
• Responsive design: Works on desktop and mobile

Real-time progressive rendering in your browser

Available Scenes

• default - Spheres with various materials on a ground plane
• cornell - Classic Cornell box with area lighting
• cornell-boxes - Cornell box with rotated boxes
• spheregrid - Grid of metallic spheres (perfect for BVH testing)
• trianglemesh - Showcase of triangle mesh geometry
• dragon - Dragon PLY mesh from PBRT book (requires downloading PLY separately)

Rendering Modes

• normal - Standard single-pass rendering
• progressive - Multi-pass progressive improvement with parallel processing

Example Commands

# Quick preview (3 passes, 25 samples)
./raytracer.exe --scene=cornell --mode=progressive --max-passes=3 --max-samples=25

# High quality render (10 passes, 200 samples)
./raytracer.exe --scene=default --mode=progressive --max-passes=10 --max-samples=200

# Use specific number of CPU cores
./raytracer.exe --scene=spheregrid --mode=progressive --workers=4

# CPU profiling
./raytracer.exe --scene=default --mode=normal --profile=cpu.prof

Performance

• Progressive Preview: First pass renders in ~25-70ms
• Multi-threaded: ~2x speedup with 4+ CPU cores
• BVH Acceleration: Up to 39x faster for complex triangle meshes
• Memory Efficient: Tile-based rendering with adaptive sampling

Architecture

• pkg/core/ - Foundation types and interfaces
• pkg/geometry/ - Shape primitives and acceleration structures
• pkg/material/ - Material implementations
• pkg/renderer/ - Ray tracing engine and progressive rendering
• pkg/scene/ - Scene management and presets
• web/ - Web interface with real-time streaming

Output

Rendered images are saved to output/<scene_name>/render_<timestamp>.png

Progressive mode saves intermediate passes: render_<timestamp>_pass_<N>.png

License

This project is licensed under the MIT License - see the LICENSE file for details.