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Code Issues 151 Wiki Activity

Space the steps towards the sun of the clouds geometrically and follow more orders of scattering

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Hirek
2026-10-17 19:01:39 +02:00
parent e1900a9cd3
commit 1152791e8c
1 changed files with 12 additions and 3 deletions
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15
shaders/clouds_march.comp
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@@ -45,6 +45,12 @@ const float CLOUD_SKY_FLOOR = 0.15;
const float CLOUD_POWDER = 6.0;
// how many of the nearest steps towards the sun see the detail noise
const int CLOUD_LIGHT_DETAIL_STEPS = 1;
// orders of the scattering the sunlight is followed through (cloud_sunlight): the higher ones reach deep into a thick cloud, so its
// shaded sides and its inside are lit through the cloud too, not only by the sky, and a big cloud close by is not a flat grey
const int CLOUD_SCATTER_OCTAVES = 6;
// how much longer every next step towards the sun is than the one before: 1 + this / steps², so the first step is short where the
// light falls off fastest (about a 30th of the reach at 4 steps) and the steps get close to even when there are many of them
const float CLOUD_LIGHT_GROWTH = 24.0;
float henyey_greenstein(float cosangle, float g)
{
@@ -77,20 +83,23 @@ float cloud_sunlight(int index, vec3 position, float cosangle, int steps, float
float reach = min(thickness, 1500.0);
float depth = 0.0;
float travelled = 0.0;
// steps growing geometrically: near the point the shape matters, far only the bulk. with steps growing evenly the first one was a
// tenth of the reach at 4 steps, and the light fell off the smooth sides of the clouds in visible bands
float growth = 1.0 + CLOUD_LIGHT_GROWTH / float(steps * steps);
float step = reach * (growth - 1.0) / (pow(growth, float(steps)) - 1.0);
for (int s = 0; s < steps; s++)
{
// growing steps: near the point the shape matters, far only the bulk
float step = reach * (float(s) + 1.0) / float(steps * (steps + 1) / 2);
vec3 point = position + sun * (travelled + 0.5 * step);
travelled += step;
// the nearest steps with the detail noise: the small billows shade one another, lit on top and grey beneath
depth += cloud_layer_density(index, point, cloud_height(point), detail && (s < CLOUD_LIGHT_DETAIL_STEPS)) * step;
step *= growth;
}
float light = 0.0;
float amount = 1.0;
float fade = 1.0;
float spread = 1.0;
for (int octave = 0; octave < 3; octave++)
for (int octave = 0; octave < CLOUD_SCATTER_OCTAVES; octave++)
{
light += amount * exp(-depth * fade) * cloud_phase(cosangle, spread) * (octave == 0 ? powder : 1.0);
amount *= 0.5;