Reddit Post Silhouette Code

shader_type spatial;

render_mode depth_test_disable, skip_vertex_transform, unshaded;

void vertex() {

    VERTEX = (MODELVIEW_MATRIX * vec4(VERTEX, 1.0)).xyz;

}

void fragment() {

    float zdepth = texture(DEPTH_TEXTURE, SCREEN_UV).r;
    float zpos = FRAGCOORD.z;

    if (zdepth < zpos) {

        ALBEDO = vec3(0,0,0);
        ALPHA = 0.5;

    } else {
        discard;
    }
}

// credit:  https://github.com/effectivearm7/occludedhighlight