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Code Issues 156 Wiki Activity

Fray the edges of the volumetric clouds with a finer noise and let their billows shade one another

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Hirek
2026-10-17 17:57:25 +02:00
parent 22bf015939
commit dd89aa5396
5 changed files with 48 additions and 15 deletions
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23
shaders/clouds_common.glsl
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@@ -14,6 +14,14 @@ const float CLOUD_FILL_EDGE = 0.45;
const float CLOUD_FILL_CORE = 0.85;
// how fast the density rises inside the edge of a cloud: above 1 the edges are crisper, the inside keeps its density
const float CLOUD_EDGE_SHARPNESS = 3.0;
// the detail noise: its tile against the tile of the shape noise and how deep it eats into the edges (times the erosion of the
// genus and the tuning of the debug window, cloud_wind.w); the finer octave of the thin edges: its tile against the detail tile,
// how far the coarser octave pushes its lookup about (in its tiles), and the density below which it is used
const float CLOUD_DETAIL_SCALE = 6.0;
const float CLOUD_EROSION = 2.0;
const float CLOUD_FINE_SCALE = 3.7;
const float CLOUD_FINE_PUSH = 0.6;
const float CLOUD_FINE_BELOW = 0.6;
float cloud_remap(float value, float low, float high, float newlow, float newhigh)
{
@@ -152,12 +160,23 @@ float cloud_layer_density(int index, vec3 position, float height, bool detail)
float density = clamp(cloud_remap(base * gradient, 1.0 - fill, 1.0, 0.0, 1.0), 0.0, 1.0) * coverage.x;
if (detail && density > 0.0 && layer.shape.w > 0.0)
{
vec4 small = textureLod(cloud_detail_noise, coords * 6.0, 0.0);
vec3 detailcoords = coords * CLOUD_DETAIL_SCALE;
vec4 small = textureLod(cloud_detail_noise, detailcoords, 0.0);
// spread over 0-1 as the worley octaves of the shape; left in their narrow band they would only thin the cloud evenly
float fbm = clamp((small.r * 0.625 + small.g * 0.25 + small.b * 0.125 - 0.30) / 0.35, 0.0, 1.0);
// the thin outer part of a cloud gets a finer octave too, its lookup pushed about by the coarser one, so the edges are frayed
// into small billows and torn bits rather than evenly rounded. the dense inside is never eaten into, so it is skipped there
float fineshare = 1.0 - smoothstep(CLOUD_FINE_BELOW * 0.5, CLOUD_FINE_BELOW, density);
if (fineshare > 0.0)
{
vec3 push = (small.gbr - 0.5) * CLOUD_FINE_PUSH;
vec4 fine = textureLod(cloud_detail_noise, detailcoords * CLOUD_FINE_SCALE + push, 0.0);
float finefbm = clamp((fine.r * 0.625 + fine.g * 0.25 + fine.b * 0.125 - 0.30) / 0.35, 0.0, 1.0);
fbm = clamp(mix(fbm, fbm * 0.65 + finefbm * 0.35, fineshare), 0.0, 1.0);
}
// wispy at the base, billowing at the top
float erosion = mix(fbm, 1.0 - fbm, clamp(h * 4.0, 0.0, 1.0));
density = clamp(cloud_remap(density, erosion * layer.shape.w * 0.7, 1.0, 0.0, 1.0), 0.0, 1.0);
density = clamp(cloud_remap(density, erosion * layer.shape.w * CLOUD_EROSION * cloud_wind.w, 1.0, 0.0, 1.0), 0.0, 1.0);
}
return min(density * CLOUD_EDGE_SHARPNESS, 1.0) * layer.shape.y;
}