game: water shader experiments

assets/shaders/water2.gdshader

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+shader_type canvas_item;
+uniform vec4 water_color : source_color = vec4(0.0, 0.0, 1.0, 1.0);
+uniform sampler2D noise_tex;     // noise texture
+uniform vec2 noise_speed = vec2(0.05, 0.01);
+uniform float noise_strength = 0.2; // how much to lighten/darken
+
+void fragment() {
+	vec2 uv = UV;
+	vec4 base_tex = texture(TEXTURE, uv);
+	float is_water = step(0.8, 1.0 - distance(base_tex.rgb, water_color.rgb));
+	
+	// Scroll UVs for noise animation
+    vec2 noise_uv = SCREEN_UV + noise_speed * TIME;
+    vec4 noise_sample = texture(noise_tex, fract(noise_uv));
+	
+	// Use noise (0..1) to brighten/darken the water color
+    float brightness = (noise_sample.r - 0.5) * 2.0 * noise_strength; 
+    vec4 animated_water = water_color + vec4(vec3(brightness), 0.0);
+
+	
+	COLOR = mix(base_tex, animated_water, is_water);
+}
+
+//void light() {
+//	// Called for every pixel for every light affecting the material.
+//	// Uncomment to replace the default light processing function with this one.
+//}