+ Vector3 normal;
+ Scalar d;
+
+ typedef enum
+ {
+ NEGATIVE = -1,
+ INTERSECT = 0,
+ POSITIVE = 1
+ } Halfspace;
+
+ Plane() {}
+ Plane(const Vector3& vector, Scalar scalar) :
+ normal(vector),
+ d(scalar) {}
+ Plane(Scalar a, Scalar b, Scalar c, Scalar scalar) :
+ normal(a, b, c),
+ d(scalar) {}
+
+
+ Scalar intersectRay(const Ray<3>& ray, Ray<3>::Intersection& intersection)
+ {
+ // solve: [(ray.point + t*ray.direction) dot normal] + d = 0
+
+ Scalar denominator = cml::dot(ray.direction, normal);
+
+ // check for parallel condition
+ if (denominator == SCALAR(0.0))
+ {
+ if (isEqual(cml::dot(ray.point, normal), -d))
+ {
+ // the ray lies on the plane
+ intersection.point = ray.point;
+ intersection.normal = normal;
+ return SCALAR(0.0);
+ }
+
+ // no solution
+ return SCALAR(-1.0);
+ }
+
+ Scalar t = (cml::dot(ray.point, normal) + d) / denominator;
+ if (t > SCALAR(0.0))
+ {
+ ray.solve(intersection.point, t);
+ intersection.normal = normal;
+ }
+
+ return t;
+ }
+
+
+ /* Causes the normal of the plane to become normalized. The scalar may also
+ * be changed to keep the equation true. Word to the wise: don't normalize
+ * a plane if the normal is the zero vector. */
+ void normalize()
+ {
+ Scalar mag = normal.length();
+
+ normal /= mag;
+ d /= mag;
+ }
+
+ /**
+ * Determine the shortest distance between a point and the plane. */
+
+ Scalar getDistanceToPoint(const Vector3& point) const
+ {
+ return cml::dot(point, normal) + d;
+ }
+
+ Halfspace intersects(const Vector3& point) const
+ {
+ Scalar distance = getDistanceToPoint(point);
+
+ if (isEqual(distance, 0.0)) return INTERSECT;
+ else if (distance < 0.0) return NEGATIVE;
+ else return POSITIVE;
+ }