float z_range = occlusion_radius*length(offset)*edge_depth_threshold;
float min_depth = project(vec3(center.xy, center.z+z_range)).z;
float max_depth = project(vec3(center.xy, center.z-z_range)).z;
float z_range = occlusion_radius*length(offset)*edge_depth_threshold;
float min_depth = project(vec3(center.xy, center.z+z_range)).z;
float max_depth = project(vec3(center.xy, center.z-z_range)).z;