Ray casting with spheres.

sphere.cpp

@@ -0,0 +1,29 @@
+#include <cmath>
+
+#include "sphere.hpp"
+
+bool Sphere::intersect(Ray & r, float & t) const {
+  float d;
+
+  float a = (r.m_direction.x * r.m_direction.x) +
+    (r.m_direction.y * r.m_direction.y) +
+    (r.m_direction.z * r.m_direction.z);
+
+  float b = (2 * r.m_direction.x * (r.m_origin.x - m_center.x)) +
+    (2 * r.m_direction.y * (r.m_origin.y - m_center.y)) +
+    (2 * r.m_direction.z * (r.m_origin.z - m_center.z));
+
+  float c = (m_center.x * m_center.x) +
+    (m_center.y * m_center.y) +
+    (m_center.z * m_center.z) +
+    (r.m_origin.x * r.m_origin.x) +
+    (r.m_origin.y * r.m_origin.y) +
+    (r.m_origin.z * r.m_origin.z) -
+    2 * ((m_center.x * r.m_origin.x) + (m_center.y * r.m_origin.y) + (m_center.z * r.m_origin.z)) - (m_radius * m_radius);
+
+  d = (b * b) - (4 * a * c);
+
+  t = (-b - sqrt(d)) / (2 * a);
+
+  return d >= 0.0f;
+}