--- /dev/null
+/*
+* Copyright (c) 2007 Erin Catto http://www.gphysics.com
+*
+* This software is provided 'as-is', without any express or implied
+* warranty. In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2Collision.h"
+
+// Collision Detection in Interactive 3D Environments by Gino van den Bergen
+// From Section 3.4.1
+// x = mu1 * p1 + mu2 * p2
+// mu1 + mu2 = 1 && mu1 >= 0 && mu2 >= 0
+// mu1 = 1 - mu2;
+// x = (1 - mu2) * p1 + mu2 * p2
+// = p1 + mu2 * (p2 - p1)
+// x = s + a * r (s := start, r := end - start)
+// s + a * r = p1 + mu2 * d (d := p2 - p1)
+// -a * r + mu2 * d = b (b := s - p1)
+// [-r d] * [a; mu2] = b
+// Cramer's rule:
+// denom = det[-r d]
+// a = det[b d] / denom
+// mu2 = det[-r b] / denom
+bool b2Segment::TestSegment(float32* lambda, b2Vec2* normal, const b2Segment& segment, float32 maxLambda) const
+{
+ b2Vec2 s = segment.p1;
+ b2Vec2 r = segment.p2 - s;
+ b2Vec2 d = p2 - p1;
+ b2Vec2 n = b2Cross(d, 1.0f);
+
+ const float32 k_slop = 100.0f * B2_FLT_EPSILON;
+ float32 denom = -b2Dot(r, n);
+
+ // Cull back facing collision and ignore parallel segments.
+ if (denom > k_slop)
+ {
+ // Does the segment intersect the infinite line associated with this segment?
+ b2Vec2 b = s - p1;
+ float32 a = b2Dot(b, n);
+
+ if (0.0f <= a && a <= maxLambda * denom)
+ {
+ float32 mu2 = -r.x * b.y + r.y * b.x;
+
+ // Does the segment intersect this segment?
+ if (-k_slop * denom <= mu2 && mu2 <= denom * (1.0f + k_slop))
+ {
+ a /= denom;
+ n.Normalize();
+ *lambda = a;
+ *normal = n;
+ return true;
+ }
+ }
+ }
+
+ return false;
+}
+
+