test other scenes and fix

core/daynight/weather_plain_shader.gdshader

@@ -0,0 +1,61 @@
+shader_type spatial;
+render_mode blend_mix, depth_draw_never, cull_disabled;
+
+// Snow globals
+global uniform float global_snow_start_time;
+global uniform float global_snow_accumulation_speed;
+global uniform float global_snow_melt_time;
+global uniform float global_snow_melt_speed;
+global uniform vec4  global_snow_color;
+
+// Rain globals
+global uniform float global_rain_intensity;
+
+// Snow parameters
+uniform float snow_edge_softness : hint_range(0.01, 0.5) = 0.15;
+uniform float snow_color_variation : hint_range(0.0, 0.15) = 0.05;
+
+// Rain wetness parameters
+uniform float wetness_darkening : hint_range(0.0, 0.5) = 0.25;
+uniform float wet_roughness : hint_range(0.0, 0.3) = 0.05;
+
+void fragment() {
+    // Snow accumulation
+    float snow_amount = 0.0;
+    if (global_snow_start_time >= 0.0) {
+        snow_amount = clamp((TIME - global_snow_start_time) * global_snow_accumulation_speed, 0.0, 1.0);
+    }
+    if (global_snow_melt_time >= 0.0) {
+        float melt = clamp((TIME - global_snow_melt_time) * global_snow_melt_speed, 0.0, 1.0);
+        snow_amount *= (1.0 - melt);
+    }
+
+    // UV-based snow mask: accumulates from the top of the quad
+    float top_mask = 1.0 - UV.y;
+    float snow_mask = smoothstep(1.0 - snow_amount, 1.0 - snow_amount + snow_edge_softness, top_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);
+    shade = mix(-snow_color_variation, snow_color_variation, shade);
+    vec3 snow_albedo = clamp(global_snow_color.rgb + vec3(shade), 0.0, 1.0);
+
+    // Rain wetness
+    float rain_int = clamp(global_rain_intensity, 0.0, 1.0);
+    float rain_factor = wetness_darkening * rain_int;
+
+    // Combine: snow takes priority over rain
+    if (snow_mask > rain_factor) {
+        ALBEDO = snow_albedo;
+        ROUGHNESS = 0.15;
+        METALLIC = 0.0;
+        ALPHA = snow_mask;
+    } else if (rain_int > 0.01) {
+        ALBEDO = vec3(0.0);
+        ROUGHNESS = wet_roughness;
+        METALLIC = 0.0;
+        ALPHA = rain_factor;
+    } else {
+        ALPHA = 0.0;
+    }
+}