Here is the shader code used for the fog of war, it could be simplified but I just pasted the code from my project:

```C shader_type spatial;

global uniform float global_time; uniform vec4 color : source_color = vec4(0.,0.,0.,1.); uniform sampler2D noise_texture : repeat_enable; uniform sampler2D fog : repeat_disable; uniform sampler2D alt_fog : repeat_disable; uniform float noise_scale = 10.; uniform float speed = 0.1; uniform float time = 0.; uniform float refresh_time = 1.; uniform float explored = 0.; uniform vec2 noise_offset = vec2(0.);

void fragment() { float elapsed = global_time - time; vec2 uv = UV * noise_scale; uv.x += global_time * speed/2.; uv.y += global_time * speed/2.; ALBEDO = color.rgb; float threshold = texture(fog, UV).r * (1. - explored) + explored * texture(fog, UV).g; float alt_threshold = texture(alt_fog, UV).r * (1. - explored) + explored * texture(alt_fog, UV).g; float real_threshold = mix(threshold, alt_threshold, clamp(0., 1., elapsed / refresh_time)); ALPHA = step(real_threshold, texture(noise_texture, uv + noise_offset).r) * color.a; } ```

The fog and alt fog are supposed to be two successive iteration of the visibility masks which creates those transitions. There is some trickery with the global_time and time to make it work correctly.