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Code Issues 157 Wiki Activity

Give the volumetric clouds lumps, sky and ground light and a fog colour by the angle from the sun

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Hirek
2026-10-16 22:25:11 +02:00
parent 2be85410ce
commit 8b929fc1da
5 changed files with 68 additions and 21 deletions
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24
shaders/clouds_common.glsl
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@@ -9,6 +9,11 @@ layout(binding = CLOUD_DETAIL_TEX) uniform sampler3D cloud_detail_noise;
layout(binding = CLOUD_COVERAGE_TEX) uniform sampler2D cloud_coverage_noise;
const float CLOUD_EARTH_RADIUS = 6360000.0;
// how much of the shape noise is left standing at the edge and in the core of a cloud area (cloud_layer_density)
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 = 2.0;
float cloud_remap(float value, float low, float high, float newlow, float newhigh)
{
@@ -134,20 +139,27 @@ float cloud_layer_density(int index, vec3 position, float height, bool detail)
vec2 plane = layer.motion.xy + cloud_noise_plane(layer, position.xz);
vec3 coords = vec3(plane.x, height + layer.extra.y * 4096.0, plane.y) * layer.shape.z;
vec4 shape = textureLod(cloud_shape_noise, coords, 0.0);
float worley = shape.g * 0.625 + shape.b * 0.25 + shape.a * 0.125;
float base = clamp(cloud_remap(shape.r, worley - 1.0, 1.0, 0.0, 1.0), 0.0, 1.0);
// the smaller cells of the worley octaves bite billows into the heaps of the perlin-worley noise; the octaves keep to a narrow
// band (clouds_noise.comp: WORLEY_FBM_LOW, WORLEY_FBM_HIGH), spread over 0-1 first
float worley = clamp((shape.g * 0.625 + shape.b * 0.25 + shape.a * 0.125 - 0.30) / 0.35, 0.0, 1.0);
float base = clamp(cloud_remap(shape.r, (1.0 - worley) * 0.35, 1.0, 0.0, 1.0), 0.0, 1.0);
// the sheets (little erosion) keep few holes, the heaps are made of lumps
base = mix(1.0, base, clamp(layer.shape.w * 2.5, 0.25, 1.0));
float density = clamp(cloud_remap(base * gradient, 1.0 - coverage.x, 1.0, 0.0, 1.0), 0.0, 1.0) * coverage.x;
// inside its area a cloud is not a solid block: the lumps of the shape noise are cut out of it, the more the nearer its edge,
// so it breaks up into single heaps with rounded tops and gaps between them. the sheets keep their base above the cut, and a
// layer closing up (broken to overcast) keeps its lumps whole, so it has no more gaps than its coverage
float fill = coverage.x * mix(mix(CLOUD_FILL_EDGE, CLOUD_FILL_CORE, coverage.y), 1.0, smoothstep(0.5, 1.0, layer.shape.x));
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);
float fbm = small.r * 0.625 + small.g * 0.25 + small.b * 0.125;
// 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);
// 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 * 0.5, 1.0, 0.0, 1.0), 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);
}
return density * layer.shape.y;
return min(density * CLOUD_EDGE_SHARPNESS, 1.0) * layer.shape.y;
}
// the same without the detail, cheaper, for the shadows and the fog