Basing world coloring works.

materials/shader/WorldColoring.gdshader

@@ -0,0 +1,22 @@
+shader_type spatial;
+
+uniform sampler2D screen_texture : hint_screen_texture, repeat_disable, filter_nearest;
+uniform sampler2D world_color_texture : hint_default_black, repeat_disable;
+
+void vertex() {
+	// Called for every vertex the material is visible on.
+}
+
+void fragment() {
+  vec4 projected_coords = INV_VIEW_MATRIX * vec4(VERTEX, 1.0);
+	
+  vec4 currentColor = textureLod(screen_texture, SCREEN_UV, 0.0);
+  vec4 worldColor = textureLod(world_color_texture, projected_coords.xz * 0.01 + vec2(0.5), 0.0);
+  vec3 colorToLuminance = vec3(0.2126, 0.7152, 0.0722);
+  ALBEDO = vec3(dot(currentColor.rgb, colorToLuminance) * 0.4) + 0.2 * currentColor.rgb + 0.4 * worldColor.rgb;
+}
+
+//void light() {
+	// Called for every pixel for every light affecting the material.
+	// Uncomment to replace the default light processing function with this one.
+//}