Amida: 2D Lighting using Radiance Cascades

This program implements 2d lighting using the Radiance Cascades algorithm by Alexander Sannikov, using the bilinear fix to prevent ringing. It also supports multiple bounces using subsurface scattering and volumetrics.

Usage

Note: This program requires a NVIDIA graphics card due to using CUDA.

Download the latest release, or compile the program yourself by installing Rust, and executing cargo run, then call the program:

> ./amida.exe world/empty256.tiff env/golden.tiff settings/size256.ron

Note that any arguments not provided will be loaded from the default files in the corresponding folder. After opening, the controls are as follows:

• Mouse buttons: Draw walls / light sources. This is configurable in the settings file (which can also add material keybindings). The defaults are:
  • Left: Draw wall
  • Middle: Draw light source
  • Right: Erase
  • Forward: Transparent red wall
  • Backward: Transparent blue wall
• Scroll wheel: Change the radius of the brush.
• Q: Draw using a square brush.
• Enter: Change the merging variant. Options:
  • 0: Stochastic bilinear
  • 1: Nearest
  • 2: Normal bilinear (4x slower)
• B: Change the number of bounces, up to 3.
• S: Save the current scene to a file. Pressing ctrl will overwrite the current file, otherwise a new file with a timestamp will be created.
• L: Reload the scene from the input file.
• Space: Pause the rendering.
• D: Show the difference map.
• E: Change the displayed cascade level.
• R: Show the raw radiance map (because some environments may not have the background be white).
• F: Show the bounce lighting.
• Esc: Close the program.

The .tiff files can be edited using GIMP or Krita - although when exporting, all metadata should be removed. All layers use linear RGB. The layers are:

• emissive: The amount of light emitted by pixels. Can be set greater than 1.
• diffuse: The diffuse color, used for bouncing. Note that diffuse bouncing is completely rotationally-symmetric, so approximately half of the light will be bounced into the object.
• opacity: The opacity of materials during bounces.
• display_emissive: The amount of added color to the final image.
• display_diffuse: The amount of the radiance added to the final image.
• display_opacity: The opacity in the final bounce. This is split from opacity to allow for light bleeding effects.

This program also supports creating a world from an input image with a palette mapping:

> ./amida.exe world/room.png env/default.tiff settings/default.tiff room-palette.ron

Will lookup the colors in the image using the mapping in room-palette.ron

Known Bugs

• The dpi scaling is broken and has to be manually adjusted. Use the settings/dpi2.ron file when having a 2x scaling.

Gallery

Any contributions to the gallery (or to other parts of this project) would be greatly appreciated.

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Join the Radiance Cascades Discord for more information and to discuss the algorithm!