X-Git-Url: https://git.dogcows.com/gitweb?p=chaz%2Fyoink;a=blobdiff_plain;f=src%2Fmoof%2Fplane.hh;fp=src%2Fmoof%2Fplane.hh;h=3de87e4e3a8ac0bb5f41334321d2c04bfb98c980;hp=0000000000000000000000000000000000000000;hb=831f04d4bc19a390415ac0bbac4331c7a65509bc;hpb=299af4f2047e767e5d79501c26444473bda64c64

diff --git a/src/moof/plane.hh b/src/moof/plane.hh
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+
+/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
+**]  All rights reserved.
+*
+* vi:ts=4 sw=4 tw=75
+*
+* Distributable under the terms and conditions of the 2-clause BSD license;
+* see the file COPYING for a complete text of the license.
+*
+**************************************************************************/
+
+#ifndef _MOOF_PLANE_HH_
+#define _MOOF_PLANE_HH_
+
+/**
+ * \file plane.hh
+ * Classes and functions related to planes.
+ */
+
+#include <moof/math.hh>
+#include <moof/shape.hh>
+
+
+namespace moof {
+
+
+template <int D> class aabb;
+template <int D> class sphere;
+
+
+/**
+ * A plane in 3-space defined by the equation Ax + By + Cz = D, where [A,
+ * B, C] is normal to the plane.
+ */
+struct plane : public shape<3>
+{
+	vector3	normal;
+	scalar	d;
+
+	enum halfspace
+	{
+		negative		= -1,
+		intersecting	=  0,
+		positive		=  1
+	};
+
+	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) {}
+
+
+	bool intersect_ray(const ray<3>& ray, ray<3>::contact& hit)
+	{
+		// solve: [(ray.point + t*ray.direction) dot normal] + d = 0
+
+		scalar denom = dot(ray.direction, normal);
+
+		// check for parallel condition
+		if (denom == SCALAR(0.0))
+		{
+			if (is_equal(dot(ray.point, normal), -d))
+			{
+				// the ray lies on the plane
+				hit.distance = SCALAR(0.0);
+				hit.normal.set(0.0, 0.0, 0.0);
+				return true;
+			}
+
+			// no solution
+			return false;
+		}
+
+		scalar numer = dot(ray.point, normal) + d;
+		hit.distance = -numer / denom;
+		if (hit.distance < SCALAR(0.0)) return false;
+
+		if (numer >= 0.0) hit.normal = normal;
+		else              hit.normal = -normal;
+		return true;
+	}
+
+
+	/* 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 distance_to_point(const vector3& point) const
+	{
+		return dot(point, normal) + d;
+	}
+
+	halfspace intersects(const vector3& point) const
+	{
+		scalar distance = distance_to_point(point);
+
+		if (is_equal(distance, 0.0)) return intersecting;
+		else if (distance < 0.0)     return negative;
+		else                         return positive;
+	}
+
+	halfspace intersects(const aabb<3>& aabb) const;
+	halfspace intersects(const sphere<3>& sphere) const;
+};
+
+
+} // namespace moof
+
+#endif // _MOOF_PLANE_HH_
+