clouds: fix terrain clipping with curved occlusion

vendor/clouds3d.js

@@ -180,17 +180,18 @@ var FRAG_SRC = [
         'return dot(d, d) / (2.0 * max(1.0, uEarthRadius));',
     '}',
     'float cloudDensity(vec3 p, float baseThresh, float soft) {',
-        'float n = fbm3(p * 0.35 + vec3(0.0, 0.0, uTime * 0.06));',
+        'float py = p.y + earthDrop(p.xz);',
+        'vec3 cp = vec3(p.x, py, p.z);',
+        'float n = fbm3(cp * 0.35 + vec3(0.0, 0.0, uTime * 0.06));',
         // The detail octave weighs at most 0.20 and fades to zero with
         // distance; past soft = 0.95 it contributes under 1 %, so the whole
         // 4-octave lookup is skipped for the (numerous) far samples.
         'if (soft < 0.95) {',
-            'float d = fbm3(p * 1.4 + vec3(uTime * 0.04, 7.3, uTime * 0.03));',
+            'float d = fbm3(cp * 1.4 + vec3(uTime * 0.04, 7.3, uTime * 0.03));',
             'n = n + d * mix(0.20, 0.0, soft);',
         '}',
         // Cloud layer between uCloudBot and uCloudTop, densest in the
         // middle (bell curve). The layer follows the Earth curvature.
-        'float py = p.y + earthDrop(p.xz);',
         'float h = clamp((py - uCloudBot) / (uCloudTop - uCloudBot), 0.0, 1.0);',
         'float profile = 4.0 * h * (1.0 - h); // bell curve',
         'profile = max(profile, 0.0);',
@@ -429,11 +430,15 @@ var FRAG_SRC = [
         // ---- CLOUDS pass ----
         // Ray-terrain intersection (used to discard clouds that are
         // entirely behind the terrain mesh).
-        'float tTerrain = (ro.y > 0.0 && rd.y < -0.001) ? -ro.y / rd.y : -1.0;',
+        'vec2 terrRoots = curvedLayerRoots(0.0, ro, rd);',
+        'float tTerrain = -1.0;',
+        'if (terrRoots.x > 0.0) tTerrain = terrRoots.x;',
+        'else if (terrRoots.y > 0.0) tTerrain = terrRoots.y;',
         'if (tTerrain > 0.0 && uElevOn > 0.5 && rd.y < -0.01) {',
             'for (int ti = 0; ti < 4; ti++) {',
                 'vec3 hp = ro + rd * tTerrain;',
-                'float dh = terrElev(hp.xz) * uElevScale - hp.y;',
+                'float terrainY = terrElev(hp.xz) * uElevScale - earthDrop(hp.xz);',
+                'float dh = terrainY - hp.y;',
                 'if (abs(dh) < 0.02) break;',
                 'tTerrain += dh / -rd.y;',
                 'if (tTerrain < 0.1 || tTerrain > 90.0) { tTerrain = -1.0; break; }',
@@ -484,6 +489,7 @@ var FRAG_SRC = [
             'p.y += (ign(gl_FragCoord.xy + vec2(float(i) * 7.13, float(i) * 3.71)) - 0.5) * stepSize;',
             'float py = p.y + earthDrop(p.xz);',
             'if (py > uCloudTop || py < uCloudBot - 0.1) break;',
+            'if (uElevOn > 0.5 && py < terrElev(p.xz) * uElevScale) break;',
             'if (tTerrain > 0.0 && t >= tTerrain) break;',
             'float cSoft = smoothstep(7.0, 20.0, t);',
             'float d = cloudDensity(p, baseThresh, cSoft);',
@@ -679,15 +685,16 @@ var CLOUD_SAMPLER_GLSL = [
         'return vec2((-b - sq) / (2.0 * a), (-b + sq) / (2.0 * a));',
     '}',
     'float cloudDensity(vec3 p, float baseThresh, float soft) {',
-        'float n = fbm3(p * 0.35 + vec3(0.0, 0.0, uTime * 0.06));',
+        'float py = p.y + earthDrop(p.xz);',
+        'vec3 cp = vec3(p.x, py, p.z);',
+        'float n = fbm3(cp * 0.35 + vec3(0.0, 0.0, uTime * 0.06));',
         // The detail octave weighs at most 0.20 and fades to zero with
         // distance; past soft = 0.95 it contributes under 1 %, so the whole
         // 4-octave lookup is skipped for the (numerous) far samples.
         'if (soft < 0.95) {',
-            'float d = fbm3(p * 1.4 + vec3(uTime * 0.04, 7.3, uTime * 0.03));',
+            'float d = fbm3(cp * 1.4 + vec3(uTime * 0.04, 7.3, uTime * 0.03));',
             'n = n + d * mix(0.20, 0.0, soft);',
         '}',
-        'float py = p.y + earthDrop(p.xz);',
         'float h = clamp((py - uCloudBot) / (uCloudTop - uCloudBot), 0.0, 1.0);',
         'float profile = 4.0 * h * (1.0 - h);',
         'profile = max(profile, 0.0);',