Real light and shadow on flat artwork

The film is the editor’s own export, cut down for the web. The Agent set the seven pictures in depth, added a warm point light and a cool ambient fill, and animated the point light across the scene; each step came as a Draft⁠ (opens in a new tab) that was previewed, then applied. Nothing was painted afterwards: every shadow is computed from the shapes of the layers in front of it.

The pictures were made with an image generator outside Keyframe, as flat coloured paper with no light, shading or shadows painted in, then imported as seven layers. In Keyframe each became a 3D layer⁠ (opens in a new tab) at its own distance, like sheets in a shadow box: the sky at the back, the ferns at the front. The windows of the cabin and the round holes in one cloud are transparent, and the light goes through them.

• Point, spot and parallel lights cast shadows; an ambient light lifts the dark sides without a direction. Each light has its colour, brightness and falloff, and all of them can be keyframed.
• A layer casts the shape of its opaque pixels on the layers behind it, and light passes through its transparent parts, so cut-outs throw patches of light. Shadow darkness and softness are settings of the light.
• The Viewer and an export draw the same frames with the same renderer, so the shadows you watch while you work are the shadows in the file.
• Which layers cast shadows, receive them or take light at all is set per layer, under Material Options⁠ (opens in a new tab).

• Rounded outline curls the edges of a layer’s shape away from the light, like thick paper.
• A normal map says which way each pixel faces. Use your own, or make one from the picture: a depth model runs on your device, free, and the picture is not uploaded.
• Self Shadow lets the raised parts of a picture shade its own lower parts, as a nose shades a cheek in low light.
• Fine Detail reads small relief, such as the grain of paper or the weave of cloth, from the picture’s light and dark, where the depth model sees none.
• Everything is described under Lit surfaces⁠ (opens in a new tab) in the manual.

The Agent⁠ (opens in a new tab) can make layers 3D and set them in depth, add and aim lights, choose the surfaces, make a normal map from depth on your device, and animate the light. Each step is a Draft: you watch it in the Viewer, then apply it or ask for changes. The light it sets is ordinary layers and keyframes, which you can change by hand afterwards. Having the Agent do it belongs to the Agent subscription, which opens soon; lighting a scene yourself is free.

In most 2D animation, light is the artist’s work: shading is painted into each picture, and a shadow is a blurred, darkened copy of a layer moved by hand. Game engines compute light, but for models and materials, not for layered artwork on a timeline. Keyframe puts a computed light into an After Effects-style layer editor, so the shadows follow the shapes you drew and move when the light moves.

It is optional. Layers stay 2D and unlit until you make them 3D and add a light, and a composition without lights looks as it always did. Painted light still works alongside: keep the shading in your pictures, add a light only where it helps, and turn off Accepts Lights for a layer that should stay exactly as painted.

• No ray tracing or global illumination: light does not bounce from one layer onto another, and there is no volumetric light.
• Self Shadow reaches only so far, a quarter of the picture’s longer side towards the light; longer shadows are cut short.
• In grazing light, Self Shadow can leave a hard edge, because the heights it works from are added up from the picture’s slopes.
• Fine Detail reads printed patterns, freckles and painted shading as relief too, since it sees only light and dark.
• A photo already has light in it: its painted-in highlights and shadows fight a new light. Flat artwork drawn without light takes it best.
• Shadow maps are limited in number; lights past the limit cast no shadows. Lighting needs a browser with WebGPU.