Building igl statically and moving to the dep scripts

Fixing dep build script on Windows and removing some warnings.

Use bundled igl by default.

Not building with the dependency scripts if not explicitly stated. This way, it will stay in
Fix the libigl patch to include C source files in header only mode.

src/libigl/igl/segment_segment_intersect.cpp

@@ -0,0 +1,67 @@
+// This file is part of libigl, a simple c++ geometry processing library.
+//
+// Copyright (C) 2016 Francisca Gil Ureta <gilureta@cs.nyu.edu>
+//
+// This Source Code Form is subject to the terms of the Mozilla Public License
+// v. 2.0. If a copy of the MPL was not distributed with this file, You can
+// obtain one at http://mozilla.org/MPL/2.0/.
+#include "segment_segment_intersect.h"
+
+#include <Eigen/Geometry>
+
+template<typename DerivedSource, typename DerivedDir>
+IGL_INLINE bool igl::segments_intersect(
+        const Eigen::PlainObjectBase <DerivedSource> &p,
+        const Eigen::PlainObjectBase <DerivedDir> &r,
+        const Eigen::PlainObjectBase <DerivedSource> &q,
+        const Eigen::PlainObjectBase <DerivedDir> &s,
+        double &a_t,
+        double &a_u,
+        double eps
+)
+{
+    // http://stackoverflow.com/questions/563198/how-do-you-detect-where-two-line-segments-intersect
+    // Search intersection between two segments
+    // p + t*r :  t \in [0,1]
+    // q + u*s :  u \in [0,1]
+
+    // p + t * r = q + u * s  // x s
+    // t(r x s) = (q - p) x s
+    // t = (q - p) x s / (r x s)
+
+    // (r x s) ~ 0 --> directions are parallel, they will never cross
+    Eigen::RowVector3d rxs = r.cross(s);
+    if (rxs.norm() <= eps)
+        return false;
+
+    int sign;
+
+    double u;
+    // u = (q − p) × r / (r × s)
+    Eigen::RowVector3d u1 = (q - p).cross(r);
+    sign = ((u1.dot(rxs)) > 0) ? 1 : -1;
+    u = u1.norm() / rxs.norm();
+    u = u * sign;
+
+    if ((u - 1.) > eps || u < -eps)
+        return false;
+
+    double t;
+    // t = (q - p) x s / (r x s)
+    Eigen::RowVector3d t1 = (q - p).cross(s);
+    sign = ((t1.dot(rxs)) > 0) ? 1 : -1;
+    t = t1.norm() / rxs.norm();
+    t = t * sign;
+
+    if (t < -eps || fabs(t) < eps)
+        return false;
+
+    a_t = t;
+    a_u = u;
+
+    return true;
+};
+
+#ifdef IGL_STATIC_LIBRARY
+template bool igl::segments_intersect<Eigen::Matrix<double, 1, 3, 1, 1, 3>, Eigen::Matrix<double, 1, 3, 1, 1, 3> >(Eigen::PlainObjectBase<Eigen::Matrix<double, 1, 3, 1, 1, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, 1, 3, 1, 1, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, 1, 3, 1, 1, 3> > const&, Eigen::PlainObjectBase<Eigen::Matrix<double, 1, 3, 1, 1, 3> > const&, double&, double&, double);
+#endif