Lite glass

The material without the shader: frost, tint and rim, and nothing to compile.

A lens gets its look from a fragment shader: every pixel measures its distance to the shape, reads the background under it, bends it and lights itself. Lite glass gives up the bending — the half that needs a shader — and keeps everything else: the frost, the tint, and the lens' two lights, evaluated on the Dart side with the shader's own formulas and drawn as triangle meshes from plain canvas geometry. No FragmentProgram, nothing to warm up, no capture on Skia, no slot in the lens budget on Impeller.

Three ways in#

It is one material with three doors. Flip the whole app, flip one lens, or use the widget directly on a surface that was never a lens.

// 1. Every lens in the app — set once, before the first lens builds.
LiquidGlassEngine.liteGlassOnSkia = true;      // Skia and the web
LiquidGlassEngine.liteGlassOnImpeller = true;  // Impeller

// 2. This lens only, on either engine.
LiquidGlassLens(
  style: const LiquidGlassStyle(liteGlass: true),
  child: child,
)

// 3. The widget itself, for a card, a row, a sheet.
LiquidGlassLite(
  shape: const LiquidGlassShape(cornerRadius: 22),
  specular: const LiquidGlassLight.specular(thickness: 8, angle: 90),
  glow: const LiquidGlassLight.glow(angle: 0, intensity: 0.8),
  blur: 3,
  color: const Color(0x33FFFFFF),
  child: child,
)

With an engine switch on, a LiquidGlassView takes no glass capture at all — the adaptive sampler is not a capture and keeps running — and every lens beneath it draws lite glass, the same thing a lens outside any view already draws. That is the way to put the material on a page that has too many lenses for the shader, or on a device that has no time for it, without touching a single lens.

What a lens keeps#

A lens drawn lite keeps its shape, its color, blur and shadow, and its magnification as a flat zoom in the frost's own filter. refractionIndex, refractionWidth and dispersion are gone — there is no edge bend. The rim is the style's specular and glow at the same numbers: thickness, sharpness, angle, spread, intensity and colour mean what they mean on a real lens, and the glow sits under the specular as it does there. The silhouette is the outline a lens clips to, so all three corner styles are reproduced exactly.

What still works, and what does not#

Lite glass changes how a lens is drawn, not what the tree around it does. Everything that never needed the shader keeps working; the two things that are the shader do not.

Where the rim gets its colour#

The shader's rim samples the background under each pixel and tints its highlight with it, so over a photograph the rim is red where it crosses red and blue where it crosses blue. Lite glass does the same thing a cheaper way: the rim is cut out of a brightened copy of the background, so its colour runs along it as the shader's does. The tint sits under it and the child over it, and neither enters the read.

What it costs#

• The frost is one backdrop read. Blur and magnification go through one filter, so adding magnification to a blur adds no read.
• The rim is a second read — two in all, what a blurred lens costs. The specular and the glow share it. With blur: 0 and magnification at 1 the frost's read goes and only the rim's is left.
• Lights that draw nothing read nothing. With the specular at intensity: 0 or thickness: 0 and no glow, there is no rim to read for, so with no blur either the widget is a plain tinted shape — the one to reach for in a long list.