Golden Hour on Demand

The time of day does more for the mood of a scene than almost anything else. The same valley is cheerful at noon, striking at sunset and quiet at night. So the sky is fully procedural — there’s no skybox photo — and it’s driven by a single sun direction, which also drives the actual sunlight and shadows so they always agree.

The sky is a shader

The sky is computed per pixel in a shader, based on the direction you’re looking and where the sun is. A few layers stack up:

• A vertical gradient from a light horizon to a deeper blue overhead. When the sun is low, the horizon colour shifts warm — the orange of sunrise and sunset.
• A glow around the sun, warm and broad when the sun is near the horizon.
• A fade to night. As the sun drops below the horizon, the whole sky is blended toward a near-black night colour.
• The sun disk itself, a bright spot with a halo.

float day = smoothstep(-0.08, 0.22, sun_height);  // 0 night .. 1 day
vec3 horizon = mix(sunset_color, day_color, ...);  // warm when the sun is low
col = mix(night_color, col, day);                  // fade out after sundown

Because it’s all derived from the sun height, moving the sun smoothly carries the sky from midday through golden hour to dark.

Night: stars, a moon, and sometimes an aurora

When it’s dark, more of the shader switches on. A sparse, faintly twinkling starfield appears overhead. A moon disk with a soft halo sits where its direction points. And occasionally — when a world rolls it — ribbons of aurora hug the horizon, built from drifting noise and coloured green shading to blue. These only appear at night, so they’re a treat you get in the worlds that have them.

Clouds

Drifting clouds are layered on using fractal noise — the same kind of many-scaled noise the terrain uses, but in 2D and slowly moving — projected onto the sky above the camera. Cloud coverage is a parameter, so some worlds are clear and others overcast.

The consistent look

Two more things make every world feel art-directed rather than raw.

Fog, including volumetric fog — fog that fills space rather than just tinting the distance. Light passing through it becomes visible as shafts (god-rays) from the sun, or from the lamp posts at night. Storms thicken it for a moodier feel.

Post-processing. After the scene is rendered, it’s run through a filmic tonemap — the same kind of curve film and cinema cameras use to handle bright and dark areas gracefully — plus a slight bump to contrast and saturation, gentle ambient shadowing in the creases, and reflections on the water. This grade is applied to every world, which is what gives them a common, slightly cinematic character no matter how different the terrain.

The nights are deliberately very dark — which is exactly why the next post exists: the warm lights that make a dark world cosy instead of bleak.