Lumen light guide

Help

Short answers to what goes wrong most often.

The frame says the effect needs WebGL

Lumen light draws with WebGL, and this browser has it turned off. Turn on the browser's graphics acceleration, update it, or try another current browser.

Tapping the picture does nothing

A tap during a run is ignored, so a run is never cut in half. Wait for it to finish, or press Replay, which always starts again at once. A run also only starts from a tap with the main mouse button or a finger.

The light does not go where I tap

Tapping only plays a run; it does not place the light. Move Light X and Light Y under Sliders instead.

The light does not swing round

In Tyndall and Aureole a run swings the light round the middle of the frame, at its distance from the middle. With Light X and Light Y both at 0.5 that distance is nothing, so the light stays still. Move either slider away from 0.5.

A slider seems to do nothing

Anisotropy is hidden in Penumbra and Alabaster, which do not use it. Base dim has no effect in the transitions until a run plays. With Intensity at 0 there is no light to change.

The transition goes the wrong way

After each finished Penumbra or Alabaster run the direction flips, so the pictures swap turns: A into B, then B into A. Tap or press Replay once more to go the other way, or press Reset to start again from picture A. Switching to Tyndall or Aureole also sends the next transition back to A into B.

My picture looks stretched

The frame takes the shape of picture A, and picture B is stretched to that shape. Crop both pictures to the same shape first. Replacing A changes the frame's shape; replacing B does not.

My picture did not change

A file the browser cannot open as an image is skipped without a message. Try a JPEG, PNG or WebP copy of it. See JPEG, PNG and WebP.

It is slow, or the page struggles with a big photo

The pictures go to the graphics card at their full size, with no resizing, so a very large photo takes more memory. Use a smaller copy on a phone or an older computer. Tyndall reads the picture up to 52 times for every pixel, so it asks the most of the graphics card, and a bigger frame costs more.

Record video did nothing

The line under the buttons says why: some browsers cannot record a canvas, or offer no video format the page can use. Try a current Chrome, Edge or Firefox.

Where do my pictures go?

Nowhere. They are opened in your browser and drawn on your graphics card. Nothing is uploaded. The pictures you add stay on this device, in this browser, so the other lab tools can open them too; × on a picture removes it.

Are there keyboard shortcuts?

The tool has none of its own. Anywhere in the lab, Ctrl K, or Cmd K on a Mac, opens the list of all tools.

On a phone

It works with a finger: tap the picture to play a run. The controls sit in a bar at the bottom of the screen; tap the bar to open them.