Initial release

src/libslic3r/Arachne/utils/linearAlg2D.hpp

@@ -0,0 +1,65 @@
+//Copyright (c) 2020 Ultimaker B.V.
+//CuraEngine is released under the terms of the AGPLv3 or higher.
+
+#ifndef UTILS_LINEAR_ALG_2D_H
+#define UTILS_LINEAR_ALG_2D_H
+
+#include "../../Point.hpp"
+
+namespace Slic3r::Arachne::LinearAlg2D
+{
+
+/*!
+     * Returns the determinant of the 2D matrix defined by the the vectors ab and ap as rows.
+     * 
+     * The returned value is zero for \p p lying (approximately) on the line going through \p a and \p b
+     * The value is positive for values lying to the left and negative for values lying to the right when looking from \p a to \p b.
+     * 
+     * \param p the point to check
+     * \param a the from point of the line
+     * \param b the to point of the line
+     * \return a positive value when \p p lies to the left of the line from \p a to \p b
+ */
+static inline int64_t pointIsLeftOfLine(const Point &p, const Point &a, const Point &b)
+{
+    return int64_t(b.x() - a.x()) * int64_t(p.y() - a.y()) - int64_t(b.y() - a.y()) * int64_t(p.x() - a.x());
+}
+
+/*!
+     * Compute the angle between two consecutive line segments.
+     *
+     * The angle is computed from the left side of b when looking from a.
+     *
+     *   c
+     *    \                     .
+     *     \ b
+     * angle|
+     *      |
+     *      a
+     *
+     * \param a start of first line segment
+     * \param b end of first segment and start of second line segment
+     * \param c end of second line segment
+     * \return the angle in radians between 0 and 2 * pi of the corner in \p b
+ */
+static inline float getAngleLeft(const Point &a, const Point &b, const Point &c)
+{
+    const Vec2i64 ba   = (a - b).cast<int64_t>();
+    const Vec2i64 bc   = (c - b).cast<int64_t>();
+    const int64_t dott = ba.dot(bc);      // dot product
+    const int64_t det  = cross2(ba, bc); // determinant
+    if (det == 0) {
+        if ((ba.x() != 0 && (ba.x() > 0) == (bc.x() > 0)) || (ba.x() == 0 && (ba.y() > 0) == (bc.y() > 0)))
+            return 0; // pointy bit
+        else
+            return float(M_PI); // straight bit
+    }
+    const float angle = -atan2(double(det), double(dott)); // from -pi to pi
+    if (angle >= 0)
+        return angle;
+    else
+        return M_PI * 2 + angle;
+}
+
+}//namespace Slic3r::Arachne
+#endif//UTILS_LINEAR_ALG_2D_H