From 53ebaeec3ebcd185ec78cb6a9934afb5b7be73ef Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop+git@gmail.com>
Date: Thu, 8 Jul 2010 18:33:39 +0000
Subject: [PATCH] end caps on extrudes working!

git-svn-id: svn://anubis/fart/trunk@279 7f9b0f55-74a9-4bce-be96-3c2cd072584d
---
 scenes/extrudes.fart |  2 +-
 shapes/Extrude.cc    |  8 ++++----
 util/Polygon.cc      | 36 +++++++++++++++++++++++++++++++++++-
 util/Polygon.h       |  3 ++-
 4 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/scenes/extrudes.fart b/scenes/extrudes.fart
index 08275c9..4c977a4 100644
--- a/scenes/extrudes.fart
+++ b/scenes/extrudes.fart
@@ -37,7 +37,7 @@ scene
             <-3, -3>
             <-1, -2>
             <1, -4>
-            <2, -1>
+            <1, -1>
         }
         offset 3
         material { color <1, 0.7, 0> }
diff --git a/shapes/Extrude.cc b/shapes/Extrude.cc
index 6bf5ebc..b42cdbb 100644
--- a/shapes/Extrude.cc
+++ b/shapes/Extrude.cc
@@ -83,7 +83,7 @@ Shape::IntersectionList Extrude::intersect(refptr<Shape> _this, const Ray & ray)
                         Vector ipoint = ray_inv[solutions.results[0]];
                         Polygon quad;
                         quad.add(p1).add(p2).add(p3).add(p4);
-                        if (quad.containsPoint(ipoint))
+                        if (quad.containsPointConvex(ipoint))
                         {
                             res.add(Intersection(_this,
                                         m_transform.transform_point(ipoint),
@@ -115,7 +115,7 @@ Shape::IntersectionList Extrude::intersect(refptr<Shape> _this, const Ray & ray)
             for (int p = 0; p < n_polygons; p++)
             {
                 refptr<Polygon> polygon = m_polygons[p];
-                if (polygon->containsPoint(ipoint))
+                if (polygon->containsPoint2D(ipoint))
                 {
                     res.add(Intersection(_this,
                                 m_transform.transform_point(ipoint),
@@ -126,7 +126,7 @@ Shape::IntersectionList Extrude::intersect(refptr<Shape> _this, const Ray & ray)
     }
     if (scale[0] > 0.0 && scale[1] > 0.0)
     {
-        a = 0, b = 0, c = 1.0, d = distance;
+        a = 0, b = 0, c = 1.0, d = -distance;
         if (ray_inv.getDirection() % Vector(a, b, c) < 0)
         {
             LinearSolver solver(  a * ray_inv.getDirection()[0]
@@ -148,7 +148,7 @@ Shape::IntersectionList Extrude::intersect(refptr<Shape> _this, const Ray & ray)
                         tp[i] = new Vector(tp[i]->mult(scale) + shift);
                         (*tp[i])[2] += distance;
                     }
-                    if (tp.containsPoint(ipoint))
+                    if (tp.containsPoint2D(ipoint))
                     {
                         res.add(Intersection(_this,
                                     m_transform.transform_point(ipoint),
diff --git a/util/Polygon.cc b/util/Polygon.cc
index b57ac67..6524fb9 100644
--- a/util/Polygon.cc
+++ b/util/Polygon.cc
@@ -5,7 +5,41 @@
 
 #define FP_EQUAL(x,y) (fabs((x)-(y)) < 1E-6)
 
-bool Polygon::containsPoint(const Vector & v)
+/*
+ * from http://local.wasp.uwa.edu.au/~pbourke/geometry/insidepoly/
+ * Return the angle between two vectors on a plane
+ * The angle is from vector 1 to vector 2, positive anticlockwise
+ * The result is between -pi -> pi
+*/
+double angle2D(double x1, double y1, double x2, double y2)
+{
+    double dtheta, theta1, theta2;
+
+    theta1 = atan2(y1,x1);
+    theta2 = atan2(y2,x2);
+    dtheta = theta2 - theta1;
+    while (dtheta > M_PI)
+        dtheta -= 2.0 * M_PI;
+    while (dtheta < -M_PI)
+        dtheta += 2.0 * M_PI;
+
+    return dtheta;
+}
+
+bool Polygon::containsPoint2D(const Vector & v) const
+{
+    double angle_sum = 0.0;
+    for (int i = 0, sz = size(); i < sz; i++)
+    {
+        Vector v1 = *(*this)[i] - v;
+        Vector v2 = *(*this)[(i+1) % sz] - v;
+        double angle = angle2D(v1[0], v1[1], v2[0], v2[1]);
+        angle_sum += angle;
+    }
+    return FP_EQUAL(angle_sum, 2.0 * M_PI);
+}
+
+bool Polygon::containsPointConvex(const Vector & v) const
 {
     double angle_sum = 0.0;
     for (int i = 0, sz = size(); i < sz; i++)
diff --git a/util/Polygon.h b/util/Polygon.h
index ffb00fd..88e73ae 100644
--- a/util/Polygon.h
+++ b/util/Polygon.h
@@ -20,7 +20,8 @@ class Polygon : public std::vector< refptr<Vector> >
             push_back(v);
             return *this;
         }
-        bool containsPoint(const Vector & v);
+        bool containsPoint2D(const Vector & v) const;
+        bool containsPointConvex(const Vector & v) const;
 };
 
 #endif