+bool CullTest(const AABB &box, const glm::mat4 &MVP) {
+ // transform corners into clip space
+ glm::vec4 corners[8] = {
+ { box.min.x, box.min.y, box.min.z, 1.0f },
+ { box.min.x, box.min.y, box.max.z, 1.0f },
+ { box.min.x, box.max.y, box.min.z, 1.0f },
+ { box.min.x, box.max.y, box.max.z, 1.0f },
+ { box.max.x, box.min.y, box.min.z, 1.0f },
+ { box.max.x, box.min.y, box.max.z, 1.0f },
+ { box.max.x, box.max.y, box.min.z, 1.0f },
+ { box.max.x, box.max.y, box.max.z, 1.0f },
+ };
+ for (glm::vec4 &corner : corners) {
+ corner = MVP * corner;
+ corner /= corner.w;
+ }
+
+ int hits[6] = { 0, 0, 0, 0, 0, 0 };
+
+ // check how many corners lie outside
+ for (const glm::vec4 &corner : corners) {
+ if (corner.x > 1.0f) ++hits[0];
+ if (corner.x < -1.0f) ++hits[1];
+ if (corner.y > 1.0f) ++hits[2];
+ if (corner.y < -1.0f) ++hits[3];
+ if (corner.z > 1.0f) ++hits[4];
+ if (corner.z < -1.0f) ++hits[5];
+ }
+
+ // if all corners are outside any given clip plane, the test is true
+ for (int hit : hits) {
+ if (hit == 8) return true;
+ }
+
+ // otherwise the box might still get culled completely, but can't say for sure ;)
+ return false;
+}
+