Render.js: A Raytracing Renderer

A Node.js raytracing renderer with RenderMan RIB format support, implemented in pure JavaScript.

Sample Output

Example render showing multi-colored spheres with reflections, realistic lighting, and antialiasing

Features

• Pure JavaScript Implementation: No external dependencies, runs entirely in Node.js
• Multi-Threaded Rendering: Automatic CPU detection and parallel processing using worker threads
• RenderMan RIB Support: Parse and render RenderMan RIB format files
• Advanced Antialiasing: Stratified sampling with quality presets
• Core Raytracing: Full raytracing pipeline with reflection support
• Lighting Models: Phong/Blinn-Phong shading with multiple light sources
• Geometry Primitives: Spheres, planes, triangles, and NURBS surfaces
• Material System: Support for different surface materials (plastic, metal, matte)
• Gamma Correction: Proper color space handling
• PPM Image Output: Generates standard PPM image files

Installation

git clone https://github.com/anders94/render.js.git
cd render.js

Note: there are no dependancies so npm install is not necessary.

Quick Start

# Run the raytracer with example scene
npm start

# Run tests to verify everything works
npm test

# Render a high-quality example
npm run render:example

# Try the NURBS examples
node src/renderer.js --rib examples/nurbs_center.rib --aa medium
node src/renderer.js --rib examples/nurbs_complex.rib --width 800 --height 600 --aa high

Usage

Basic Usage (Default Scene)

node src/renderer.js

Render from RIB File

# Basic sphere scene
node src/renderer.js --rib examples/simple.rib

# NURBS surface examples  
node src/renderer.js --rib examples/nurbs_center.rib
node src/renderer.js --rib examples/nurbs_simple.rib

Custom Resolution and Quality

# Using manual sample count
node src/renderer.js --width 800 --height 600 --samples 4 --output my_render.ppm

# Using quality presets (recommended)
node src/renderer.js --width 800 --height 600 --aa high --output my_render.ppm

# With custom gamma correction
node src/renderer.js --aa medium --gamma 1.8 --output linear.ppm

# Multi-threaded high quality rendering
node src/renderer.js --width 800 --height 600 --aa high --threads 8

Command Line Options

• --rib <file>: Render from RIB file
• --width <number>: Image width (default: 400)
• --height <number>: Image height (default: 300)
• --samples <number>: Samples per pixel for anti-aliasing (default: 1)
• --aa <quality>: Antialiasing quality preset: none, low, medium, high, ultra
• --gamma <number>: Gamma correction value (default: 2.2)
• --no-stratified: Disable stratified sampling (use random sampling)
• --single-threaded: Disable multi-threading (use single thread)
• --threads <number>: Number of threads to use (default: auto-detect)
• --output <file>: Output filename (default: output.ppm)
• --help: Show help message

Antialiasing Quality Levels

• none: No antialiasing (1 sample per pixel) - fastest
• low: Light antialiasing (4 samples per pixel) - good performance
• medium: Good quality (9 samples per pixel) - balanced quality/speed
• high: High quality (16 samples per pixel) - better quality
• ultra: Maximum quality (25 samples per pixel) - best quality

RIB Format Support

The renderer supports a subset of RenderMan RIB commands:

Supported Commands

• WorldBegin / WorldEnd
• AttributeBegin / AttributeEnd
• TransformBegin / TransformEnd
• Translate x y z
• Rotate angle x y z
• Scale sx sy sz
• Color [r g b]
• Surface "material"
• Sphere radius zmin zmax thetamax
• Polygon (converted to triangles)
• NuPatch (NURBS surfaces with full B-spline evaluation)
• LightSource "type"

Supported Surface Materials

• plastic: Standard plastic material with moderate reflection
• metal: Highly reflective metallic material
• matte: Non-reflective diffuse material

NURBS Surface Support

The renderer includes full support for Non-Uniform Rational B-Spline (NURBS) surfaces via the NuPatch command:

• Complete B-spline evaluation using Cox-de Boor recursion algorithm
• Arbitrary degree surfaces with custom knot vectors
• Tessellation-based ray intersection for reliable rendering
• Multi-threaded NURBS rendering with proper serialization
• Standard RenderMan syntax compatibility

Example NURBS syntax:

NuPatch 3 3 "0 0 0 1 1 1" 0 1 3 3 "0 0 0 1 1 1" 0 1 "P" [
    -1.0 -1.0 -3.0    0.0 -1.0 -3.0    1.0 -1.0 -3.0
    -1.0  0.0 -3.0    0.0  0.0 -3.0    1.0  0.0 -3.0
    -1.0  1.0 -3.0    0.0  1.0 -3.0    1.0  1.0 -3.0
]

Testing

The raytracer includes a comprehensive testing framework that validates output using deterministic seeding:

# Run all tests
npm test

# Generate reference images for tests
npm run test:references

# Clean test output files
npm run test:clean

# Compare two images manually
npm run image:diff image1.ppm image2.ppm

Test Features

• Bit-for-bit comparison of rendered images with reference images
• Multi-threading validation ensures single and multi-threaded renders are identical
• Deterministic seeding for reproducible test results
• Automatic reference generation when references don't exist
• Comprehensive reporting with detailed failure analysis

Architecture

The renderer is built with a modular architecture:

• math.js: Vector math, matrices, rays, and color utilities
• geometry.js: Geometric primitives and scene management
• rib-parser.js: RenderMan RIB file parser
• raytracer.js: Core raytracing engine and camera system
• multi-threaded-raytracer.js: Multi-threading implementation with worker threads
• random.js: Deterministic random number generator for reproducible results
• image-output.js: Image file generation (PPM format)
• renderer.js: Main application and command-line interface

Example RIB File

##RenderMan RIB-Structure 1.1
version 3.03

Format 400 300 1
Projection "perspective" "fov" [45]

WorldBegin

LightSource "distantlight" 1 "from" [1 1 1] "to" [0 0 0]

AttributeBegin
Color [0.8 0.2 0.2]
Surface "plastic"
Sphere 0.5 -0.5 0.5 360
AttributeEnd

WorldEnd

Performance Notes

• Rendering time increases significantly with resolution and sample count
• Multi-Threading:
  • Multi-threaded rendering is enabled by default and automatically uses all available CPU cores
  • Performance improvement scales with CPU core count (typically 2-8x faster)
  • Use --threads N and --seed to seed the random number generation for debugging or comparison
• Antialiasing Options:
  • --aa none: Fastest, aliased edges
  • --aa low: 4x slower than none, removes most aliasing
  • --aa medium: 9x slower, good quality for most scenes
  • --aa high: 16x slower, high quality for final renders
  • --aa ultra: 25x slower, maximum quality
• Stratified vs Random Sampling:
  • Stratified sampling (default) provides better quality and more even noise distribution
  • Random sampling (--no-stratified) may be faster but with more noise

Performance Tips

• Use multi-threading for production renders (enabled by default)
• Start with --aa medium for quality/speed balance
• Use lower resolutions for testing and development
• Consider --threads N where N is slightly less than your CPU cores for better system responsiveness

Viewing Output

PPM files can be viewed with most image viewers or converted to other formats:

# Convert to PNG using ImageMagick
convert output.ppm output.png

# View directly (on macOS)
open output.ppm