Lumen light guide

Overview

Lumen light shines a light through a haze made from the picture itself, and can use that light to carry one picture into another.

A pale figure before tall spires fills a round window in the middle, with warm white light and traces of a gold-haloed figure towards the edges
The Burn through preset partway through: picture B opens out around the light in the middle, with a warm glow at its edge.

The picture is treated as a haze: its bright parts glow and also block light, its dark parts let light pass. Light scattered by haze becomes visible, the Tyndall effect. See volumetric light and luminance.

For each pixel the tool steps along the line towards a light point and adds up the light it meets, dimmed by the haze on the way. This stepping is a form of raymarching, worked out for each pixel in a fragment shader on the GPU.

The Light mode menu has four ways to use it. Tyndall darkens the picture and draws god rays from the light through it. Aureole spreads a short, streaky glow off the bright parts, a kind of halo. Both light one picture, and a run swings the light once round the middle of the frame. See orbit sweep.

Penumbra and Alabaster are an image transition from picture A to picture B. In Penumbra, B opens out from around the light, and A gives way sooner where it is bright, a burn through. In Alabaster, B shows first where it is light and thin, as if lit from behind. See picture A and picture B, backlight and alabaster. After each of these runs the direction flips.

Eight presets set the mode and every slider at once. You can swap in your own two pictures, and keep a PNG or a video.

Open Lumen light Start here

In this guide

  1. StartWhat you need and your first light in six steps.
  2. Every controlEvery control in the panel, one line each.
  3. Three looksThree presets caught partway through, and how each was made.
  4. Keep your workThe PNG and the video.
  5. HelpWhat to do when something goes wrong.

It runs in your browser with WebGL. Your pictures stay on your device and nothing is uploaded. A mouse, a trackpad, a pen and a finger all work.