improve snow

core/daynight/weather_overlay.gdshader

@@ -16,6 +16,7 @@ global uniform float global_snow_cap_flatness_start = 0.72;
 global uniform float global_snow_cap_flatness_end  = 0.96;
 global uniform float global_snow_cap_noise_scale   = 0.22;
 global uniform float global_snow_cap_noise_strength = 0.18;
+const float SNOW_VISUAL_RESPONSE = 0.55;
 uniform float snow_noise_scale : hint_range(0.01, 1.0) = 0.15;
 uniform float snow_edge_softness : hint_range(0.01, 0.5) = 0.2;
 uniform float snow_roughness_variation : hint_range(0.0, 0.3) = 0.15;
@@ -86,6 +87,18 @@ float get_snow_progress() {
     return snow_progress;
 }
 
+float get_visual_snow_progress(float snow_progress) {
+    return pow(clamp(snow_progress, 0.0, 1.0), SNOW_VISUAL_RESPONSE);
+}
+
+float get_snow_noise_mask(vec3 world_pos, float snow_progress) {
+    float detail_noise = texture(noise_texture, world_pos.xz * snow_noise_scale).r;
+    float broad_noise = texture(noise_texture, world_pos.xz * snow_noise_scale * 0.35 + vec2(19.1, 7.4)).r;
+    float combined_noise = mix(detail_noise, broad_noise, 0.35);
+    float threshold = mix(0.92, 0.08, snow_progress);
+    return smoothstep(threshold - 0.18, threshold + 0.18, combined_noise);
+}
+
 float ripple_ring(vec2 uv, float time_offset) {
     float d = length(uv);
     float ring = sin(d * 30.0 - TIME * ripple_speed + time_offset) * 0.5 + 0.5;
@@ -94,7 +107,7 @@ float ripple_ring(vec2 uv, float time_offset) {
 }
 
 void vertex() {
-    float snow_progress = get_snow_progress();
+    float snow_progress = get_visual_snow_progress(get_snow_progress());
     float snow_accumulation = snow_progress * global_snow_max_accumulation;
     vec3 world_pos = (MODEL_MATRIX * vec4(VERTEX, 1.0)).xyz;
     vec3 world_normal = normalize((MODEL_MATRIX * vec4(NORMAL, 0.0)).xyz);
@@ -104,7 +117,7 @@ void vertex() {
         global_snow_cap_flatness_end,
         world_normal.y
     );
-    float accumulation_growth = smoothstep(0.08, 0.65, snow_progress);
+    float accumulation_growth = smoothstep(0.02, 0.45, snow_progress);
     float cap_noise = fbm(world_pos.xz * global_snow_cap_noise_scale + vec2(11.3, 4.7));
     float cap_variation = mix(1.0 - global_snow_cap_noise_strength, 1.0 + global_snow_cap_noise_strength, cap_noise);
 
@@ -118,6 +131,8 @@ void fragment() {
     vec3 world_pos = (INV_VIEW_MATRIX * vec4(VERTEX, 1.0)).xyz;
     vec3 world_normal = normalize((INV_VIEW_MATRIX * vec4(NORMAL, 0.0)).xyz);
     float facing_up = clamp(world_normal.y, 0.0, 1.0);
+    vec3 geometric_normal = normalize(cross(dFdx(world_pos), dFdy(world_pos)));
+    float snow_facing_up = max(facing_up, abs(geometric_normal.y));
     float noise_val = texture(noise_texture, world_pos.xz * snow_noise_scale).r;
 
     //Snow
@@ -127,14 +142,15 @@ void fragment() {
     float snow_edge = smoothstep(
         global_snow_threshold - snow_edge_softness,
         global_snow_threshold + snow_edge_softness,
-        facing_up
+        snow_facing_up
     );
     float flat_accumulation = smoothstep(0.0, 0.35, v_snow_cap_mask) * snow_accumulation;
+    float snow_noise_mask = get_snow_noise_mask(world_pos, snow_progress);
     float snow_variation = mix(0.75, 1.15, noise_val);
-    float snow_coverage = clamp(snow_progress * snow_variation + flat_accumulation * 0.25, 0.0, 1.0);
+    float snow_coverage = clamp(mix(snow_progress * 0.35, snow_progress * snow_variation, snow_noise_mask) + flat_accumulation * 0.15, 0.0, 1.0);
     float snow_factor = max(snow_edge * snow_coverage, flat_accumulation);
     float snow_opacity = clamp(snow_factor, 0.0, 1.0);
-    snow_opacity = max(snow_opacity, flat_accumulation * 0.9);
+    snow_opacity = max(snow_opacity, flat_accumulation * mix(0.45, 0.9, snow_noise_mask));
 
     float shade = mix(-snow_color_variation, snow_color_variation, noise_val);
     vec3 snow_albedo = clamp(global_snow_color.rgb + vec3(shade), 0.0, 1.0);