move human I/O related stuff into separate file

[blank.git] / src / geometry.cpp

diff --git a/src/geometry.cpp b/src/geometry.cpp
index df48ad3deac2c440f66d89f8fb69e69aac1e9b88..44217e981b49601c68be580eead0385efa6b45e2 100644 (file)
--- a/src/geometry.cpp
+++ b/src/geometry.cpp
@@ -126,4 +126,42 @@ bool Intersection(
        return true;
 }
 
+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;
+}
+
 }