Ray function a calculate how close it passes to a line defined by 2 points

2 files changed, 20 insertions, 0 deletions

diff --git a/lib/ray.cpp b/lib/ray.cpp
new file mode 100644
index 0000000..1e30ae4
--- /dev/null
+++ b/lib/ray.cpp
@@ -0,0 +1,18 @@
+#include "ray.hpp"
+
+float
+Ray::distanceToLine(const glm::vec3 & p1, const glm::vec3 & e1) const
+{
+	// https://en.wikipedia.org/wiki/Skew_lines
+	const auto diff = p1 - e1;
+	const auto d1 = glm::normalize(diff);
+	const auto &p2 = start, &d2 = direction;
+	const auto n = glm::cross(d1, d2);
+	const auto n2 = glm::cross(d2, n);
+	const auto c1 = p1 + (glm::dot((p2 - p1), n2) / glm::dot(d1, n2)) * d1;
+	const auto difflength = glm::length(diff);
+	if (glm::length(c1 - p1) > difflength || glm::length(c1 - e1) > difflength) {
+		return std::numeric_limits<float>::infinity();
+	}
+	return glm::abs(glm::dot(n, p1 - p2));
+}
diff --git a/lib/ray.hpp b/lib/ray.hpp
index 4c0710a..bce4a30 100644
--- a/lib/ray.hpp
+++ b/lib/ray.hpp
@@ -8,4 +8,6 @@ public:
 
 	glm::vec3 start;
 	glm::vec3 direction;
+
+	float distanceToLine(const glm::vec3 & a, const glm::vec3 & b) const;
 };