some code reorganization

[blank.git] / src / model / geometry.cpp

diff --git a/src/model/geometry.cpp b/src/model/geometry.cpp
new file mode 100644 (file)
index 0000000..416d930
--- /dev/null
+++ b/src/model/geometry.cpp
@@ -0,0 +1,106 @@
+#include "geometry.hpp"
+
+#include <limits>
+
+
+namespace blank {
+
+bool Intersection(
+       const Ray &ray,
+       const AABB &aabb,
+       const glm::mat4 &M,
+       float *dist,
+       glm::vec3 *normal
+) noexcept {
+       float t_min = 0.0f;
+       float t_max = std::numeric_limits<float>::infinity();
+       const glm::vec3 aabb_pos(M[3].x, M[3].y, M[3].z);
+       const glm::vec3 delta = aabb_pos - ray.orig;
+
+       glm::vec3 t1(t_min, t_min, t_min), t2(t_max, t_max, t_max);
+
+       for (int i = 0; i < 3; ++i) {
+               const glm::vec3 axis(M[i].x, M[i].y, M[i].z);
+               const float e = glm::dot(axis, delta);
+               const float f = glm::dot(axis, ray.dir);
+
+               if (std::abs(f) > std::numeric_limits<float>::epsilon()) {
+                       t1[i] = (e + aabb.min[i]) / f;
+                       t2[i] = (e + aabb.max[i]) / f;
+
+                       t_min = std::max(t_min, std::min(t1[i], t2[i]));
+                       t_max = std::min(t_max, std::max(t1[i], t2[i]));
+
+                       if (t_max < t_min) {
+                               return false;
+                       }
+               } else {
+                       if (aabb.min[i] - e < 0.0f || -aabb.max[i] - e > 0.0f) {
+                               return false;
+                       }
+               }
+       }
+
+       glm::vec3 min_all(min(t1, t2));
+
+       if (dist) {
+               *dist = t_min;
+       }
+       if (normal) {
+               glm::vec4 norm(0.0f);
+               if (min_all.x > min_all.y) {
+                       if (min_all.x > min_all.z) {
+                               norm.x = t2.x < t1.x ? 1 : -1;
+                       } else {
+                               norm.z = t2.z < t1.z ? 1 : -1;
+                       }
+               } else if (min_all.y > min_all.z) {
+                       norm.y = t2.y < t1.y ? 1 : -1;
+               } else {
+                       norm.z = t2.z < t1.z ? 1 : -1;
+               }
+               norm = M * norm;
+               *normal = glm::vec3(norm);
+       }
+       return true;
+}
+
+bool CullTest(const AABB &box, const glm::mat4 &MVP) noexcept {
+       // 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;
+}
+
+}