improve snow

core/daynight/weather_plain_shader.gdshader

@@ -8,7 +8,9 @@ global uniform float global_snow_melt_time = -1.0;
 global uniform float global_snow_melt_speed = 0.1;
 global uniform float global_snow_amount = 0.0;
 global uniform vec4  global_snow_color;
+const float SNOW_VISUAL_RESPONSE = 0.55;
 uniform float snow_edge_softness : hint_range(0.01, 0.5) = 0.15;
+uniform float snow_noise_scale : hint_range(0.01, 1.0) = 0.15;
 uniform float snow_color_variation : hint_range(0.0, 0.15) = 0.05;
 
 
@@ -50,6 +52,18 @@ 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);
+}
+
 void fragment() {
 	vec3 world_pos = (INV_VIEW_MATRIX * vec4(VERTEX, 1.0)).xyz;
 
@@ -57,14 +71,15 @@ void fragment() {
 	float facing_up = 1.0;
 
 	// Snow accumulation
-	float snow_amount = get_snow_progress();
+	float snow_amount = get_visual_snow_progress(get_snow_progress());
 
-	// Plain surfaces fade in uniformly to avoid patchy strip-like accumulation.
-	float snow_mask = smoothstep(0.0, 1.0, snow_amount);
+	// Plain surfaces accumulate through world-space noise so flat snow is not uniform.
+	float snow_noise_mask = get_snow_noise_mask(world_pos, snow_amount);
+	float snow_mask = mix(snow_amount * 0.35, snow_amount, snow_noise_mask);
 	snow_mask *= step(0.01, snow_amount);
 
 	// Snow color with slight variation
-	float shade = fract(sin(dot(UV, vec2(12.9898, 78.233))) * 43758.5453);
+	float shade = texture(noise_texture, world_pos.xz * snow_noise_scale * 2.0 + vec2(3.7, 11.2)).r;
 	shade = mix(-snow_color_variation, snow_color_variation, shade);
 	vec3 snow_albedo = clamp(global_snow_color.rgb + vec3(shade), 0.0, 1.0);