tinyusdz/tools/hdrgen/CHANGELOG.md

HDRGen Changelog

Version 1.1.0 (2025-11-06)

✨ New Features

Image Transformations

• Rotation Support - Rotate environment maps around Y axis

  • Use --rotation <degrees> (positive = counterclockwise)
  • Bilinear filtering for smooth results
  • Useful for adjusting lighting direction

• Intensity Scaling - Global intensity multiplier

  • Use --intensity-scale <factor> or --scale <factor>
  • Quickly adjust overall brightness
  • Apply after preset generation

LDR Output Formats

• PNG Output - 8-bit RGB PNG format

  • Automatic tone mapping from HDR
  • Simplified implementation (no compression)
  • Use --format png or -f png

• BMP Output - 24-bit RGB BMP format

  • Uncompressed bitmap format
  • Widely compatible
  • Use --format bmp or -f bmp

• JPEG Placeholder - JPEG support noted

  • Currently converts to BMP
  • Requires jpeg-js library for true JPEG encoding
  • Use --format jpg or --format jpeg

Tone Mapping

• Multiple Tone Mapping Methods

  • simple - Exposure + clamp
  • reinhard - Reinhard operator (default)
  • aces - ACES filmic tone curve
  • Use --tonemap-method <method>

• Exposure Control

  • --exposure <ev> - Exposure adjustment in EV stops
  • Default: 0.0
  • Positive values brighten, negative darken

• Gamma Correction

  • --gamma <value> - Gamma correction for display
  • Default: 2.2 (standard for sRGB displays)
  • Adjustable for different display profiles

🔧 API Changes

HDRGenerator.generate() new options:

{
  rotation: 0,              // Rotation in degrees
  intensityScale: 1.0,      // Intensity multiplier
  format: 'hdr',            // Now supports: hdr, exr, png, bmp, jpg
  tonemapOptions: {         // For LDR output
    exposure: 0.0,
    gamma: 2.2,
    method: 'reinhard'
  }
}

New Classes Exported:

• ImageTransform - Image rotation and scaling utilities
• ToneMapper - HDR to LDR tone mapping
• LDRWriter - LDR format writers (PNG, BMP, JPEG)

📝 Examples

Generate LDR preview:

hdrgen -p sun-sky -f png --exposure 1.0 -o output/sky_preview.png

Rotate environment 90 degrees:

hdrgen -p studio --rotation 90 -o output/studio_rotated.hdr

Scale intensity 2x and output as BMP:

hdrgen -p studio --intensity-scale 2.0 -f bmp -o output/studio_bright.bmp

ACES tone mapping:

hdrgen -p sun-sky -f png --tonemap-method aces --exposure -0.5 -o output/sky_aces.png

🐛 Bug Fixes

• Fixed CRC32 calculation in PNG writer (was producing negative values)
• Added unsigned 32-bit coercion for correct CRC generation

📊 Code Statistics

• New Code: ~400 lines
• Total Code: ~1,500 lines
• New Classes: 3 (ImageTransform, ToneMapper, LDRWriter)
• New Formats: 3 (PNG, BMP, JPEG placeholder)

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Version 1.0.0 (2025-11-06)

Initial Release

• HDR/EXR environment map generation
• Three presets: white-furnace, sun-sky, studio
• Lat-long and cubemap projections
• Pure Node.js implementation (zero dependencies)
• Comprehensive documentation

Features

• Presets:

  • White Furnace - Energy conservation testing
  • Sun & Sky - Procedural outdoor environment
  • Studio Lighting - 3-point lighting setup

• Formats:

  • HDR (Radiance RGBE) - Fully implemented
  • EXR (OpenEXR) - Stub implementation

• Projections:

  • Lat-long (equirectangular)
  • Cubemap (6 faces)

• CLI:

  • Comprehensive command-line interface
  • Preset-specific options
  • Resolution control

• Documentation:

  • Complete README (15KB)
  • Quick start guide
  • API documentation
  • DCC integration guides

Code Statistics

• Total Code: ~1,100 lines
• Test Coverage: 8 unit tests
• Examples: 7+ preset variations