X-Git-Url: http://git.localhorst.tv/?a=blobdiff_plain;f=src%2Fmodel%2Fgeometry.cpp;fp=src%2Fmodel%2Fgeometry.cpp;h=416d930c4f68d0c24a0f690851264b98556b855b;hb=b7d09e1e35ef90282c97509e0020b20db3c7ea9f;hp=0000000000000000000000000000000000000000;hpb=e53a0e2e711a7d8bd9b0ddacd1360aa14370643f;p=blank.git

diff --git a/src/model/geometry.cpp b/src/model/geometry.cpp
new file mode 100644
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;
+}
+
+}