Godot 4 depth fog on unshaded

godot4_depth_fog.gdshader

// depth fog is something like this

shader_type spatial;
render_mode blend_mix,depth_draw_opaque,cull_back,diffuse_burley,specular_schlick_ggx,unshaded;

uniform sampler2D depth_tex:hint_depth_texture;

void vertex() {
	
}

void fragment() {

  ALBEDO = vec3(1.,0.,0.);
  
  const vec3 fog_color = vec3(0.,1.,1.); //replace with sky texture or anything
  const float depth_far = 10.;

  float depth = texture(depth_tex, SCREEN_UV).r;
  depth = depth * 2.0 - 1.0;
  float z = -PROJECTION_MATRIX[3][2] / (depth + PROJECTION_MATRIX[2][2]);
  float x = (SCREEN_UV.x * 2.0 - 1.0) * z / PROJECTION_MATRIX[0][0];
  float y = (SCREEN_UV.y * 2.0 - 1.0) * z / PROJECTION_MATRIX[1][1];
  z*=1./depth_far;
  depth=1.+z;
  depth=clamp(depth,0.,1.);

  ALBEDO = mix(fog_color,ALBEDO,depth);
	
	METALLIC = 0.001;
	ROUGHNESS = 0.001;
	SPECULAR = 0.001;
}