Depth based fade (Fog of war)

This shader blends the environment with a selected color based on how deep the environment penetrates the mesh. Similar to Fog of War.

Shader code

shader_type spatial;

render_mode unshaded;

uniform sampler2D screen_texture : hint_screen_texture, repeat_disable, filter_nearest;
uniform sampler2D depth_texture : hint_depth_texture, repeat_disable, filter_nearest;
uniform float max_visible_depth = 3.0;
uniform vec4 fog_color: source_color = vec4(0.0, 0.0, 0.0, 1.0);

float get_linear_depth(float log_depth, vec2 screen_uv, mat4 inv_proj_mat) {
	vec4 ndc = vec4(screen_uv * 2.0 - 1.0, log_depth, 1.0);
    vec4 upos = inv_proj_mat * ndc;
	vec3 pixel_pos = upos.xyz / upos.w;
	return -pixel_pos.z;
}

void fragment() {
	vec3 frag_world_pos = (INV_VIEW_MATRIX * vec4(VERTEX, 1.0)).xyz;
	vec3 camera_world_pos = (INV_VIEW_MATRIX * vec4(0.0, 0.0, 0.0, 1.0)).xyz;
	vec3 camera_dir = normalize(frag_world_pos - camera_world_pos);
	vec3 world_normal = normalize((INV_VIEW_MATRIX * vec4(NORMAL, 0.0)).xyz);
	
    float log_depth = textureLod(depth_texture, SCREEN_UV, 0.0).r;
	vec4 screen_albedo = textureLod(screen_texture, SCREEN_UV, 0.0);
	float linear_depth = get_linear_depth(log_depth, SCREEN_UV, INV_PROJECTION_MATRIX);
	float surface_depth = get_linear_depth(FRAGCOORD.z, SCREEN_UV, INV_PROJECTION_MATRIX);
	float penetration_depth = linear_depth - surface_depth;
	float effective_depth = -max_visible_depth / dot(world_normal, camera_dir);
	float mix_percent = clamp(penetration_depth / effective_depth, 0.0, 1.0);
	ALBEDO = mix(screen_albedo, fog_color, mix_percent).rgb;
}

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