+namespace {
+
+struct QueueCompare {
+ explicit QueueCompare(const glm::ivec3 &base)
+ : base(base) { }
+ bool operator ()(const glm::ivec3 &left, const glm::ivec3 &right) const noexcept {
+ const glm::ivec3 ld(left - base);
+ const glm::ivec3 rd(right - base);
+ return
+ ld.x * ld.x + ld.y * ld.y + ld.z * ld.z <
+ rd.x * rd.x + rd.y * rd.y + rd.z * rd.z;
+ }
+ const glm::ivec3 &base;
+};
+
+}
+