Watercolour Shader Image

A procedural landscape — low sun, two hill ranges, still water — painted in one fragment shader as layered watercolour washes that bloom in wet, then dry into darker edges with granulating pigment and paper tooth; the pointer re-wets the paper.

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Techniques: signed-distance washes in a fragment shader
multiplicative pigment layering
fbm-warped bleeding edges
edge darkening on drying
granulation and paper-tooth pooling
noise-staggered wet-to-dry reveal
pointer bloom ring buffer
render-on-demand loop
Tags: #watercolour #painting #paper #shader #procedural #illustration #landscape #fragment shader #art
Inspired by: Editorial and cultural sites that render their illustrations as live watercolour — washes that bleed in while the paper is wet and dry into hard, darker edges.
Added: 9 Oct 2026

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Changes re-run the demo and rewrite the prompt so what you copy is exactly what you see.

BleedHow far washes feather and wander while wet0.55Granulation0.6Paper strengthPaper tooth and how much pigment pools in it0.55PaletteDry timeWet-to-dry reveal on load and on palette change4s

The illustration is five washes defined by signed distances (sky above the waterline, the sun disc and its broken reflection, a far ridge, a near headland, the water), multiplied onto a warm paper colour in painting order, so later washes glaze over earlier ones exactly like transparent pigment. Every lookup goes through an fbm warp whose strength grows with wetness, and every boundary is feathered by fw = 0.003 + 0.07 · bleed · wet: while the paper is wet the washes are pale and wander; as uWet falls to 0 the edges tighten and pigment pools along them (edge darkening). Granulation is two octaves of high-frequency value noise plus the paper’s own height field, and the deckle stops the paint short of the sheet with a ragged border. Pointer moves push wet spots into an 8-slot ring buffer that dries exponentially; each spot lifts pigment and leaves a faint darker back-run ring.

Gotchas: multiply the deckle mask into the edge-darkening term too, not just the base density, or pooled edges draw thin lines across the bare paper margin. Don’t give hills a lower boundary at the waterline — a second pooled edge there reads as a ruled pencil line; fade them out with a 0.006 smoothstep instead. Keep the reveal tweens outside the gsap.context() you revert on knob changes, otherwise reverting rewinds the painting to wet paper. The shader is static once dry, so render only while something is wet or animating.

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