From 76f7bfb93f7727a25e14e501b4e3d48e4cf15685 Mon Sep 17 00:00:00 2001
From: Victor <melnikukr@mail.ru>
Date: Sun, 2 Mar 2014 20:52:20 +0200
Subject: [PATCH] =?UTF-8?q?=D0=94=D0=BE=D0=B1=D0=B0=D0=B2=D0=BB=D0=B5?=
 =?UTF-8?q?=D0=BD=20TriangleClip?=
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---
 src/com/annimon/graphics/Clip.java         |   4 +-
 src/com/annimon/graphics/Point.java        |   2 +-
 src/com/annimon/graphics/TriangleClip.java | 111 +++++++++++++++++++++
 3 files changed, 114 insertions(+), 3 deletions(-)
 create mode 100644 src/com/annimon/graphics/TriangleClip.java

diff --git a/src/com/annimon/graphics/Clip.java b/src/com/annimon/graphics/Clip.java
index 534166c..25ba74f 100644
--- a/src/com/annimon/graphics/Clip.java
+++ b/src/com/annimon/graphics/Clip.java
@@ -27,7 +27,7 @@ public class Clip extends Rect {
     public double[] clip(double x1, double y1, double x2, double y2) {
         int c1 = getClipCode(x1, y1);
         int c2 = getClipCode(x2, y2);
-        while (c1 != 0 || (c2 != 0)) {
+        while (c1 != 0 || c2 != 0) {
             if (c1 == 0 && c2 == 0) {
                 return new double[] { x1, y1, x2, y2 };
             }
@@ -66,7 +66,7 @@ public class Clip extends Rect {
             }
         }
         return new double[] { x1, y1, x2, y2 };
-    } 
+    }
     
     public int getClipCode(double x, double y) {
         int xmin = (x < super.x) ? 1 : 0;
diff --git a/src/com/annimon/graphics/Point.java b/src/com/annimon/graphics/Point.java
index 7c2c83b..841f656 100644
--- a/src/com/annimon/graphics/Point.java
+++ b/src/com/annimon/graphics/Point.java
@@ -6,7 +6,7 @@ package com.annimon.graphics;
  */
 public class Point {
 
-    private double x, y;
+    public double x, y;
 
     public Point() {
         x = y = 0;
diff --git a/src/com/annimon/graphics/TriangleClip.java b/src/com/annimon/graphics/TriangleClip.java
new file mode 100644
index 0000000..43b6b88
--- /dev/null
+++ b/src/com/annimon/graphics/TriangleClip.java
@@ -0,0 +1,111 @@
+package com.annimon.graphics;
+
+/**
+ *
+ * @author aNNiMON
+ */
+public class TriangleClip extends Clip {
+    
+    private Polygon poly;
+
+    public TriangleClip(Point[] points) {
+        super(0, 0, 0, 0);
+        poly = new Polygon(points);
+    }
+    
+    @Override
+    public double[] clip(double x1, double y1, double x2, double y2) {
+        return clipCyrusBeck(new Point(x1, y1), new Point(x2, y2), calcNormals(poly, poly.v));
+    }
+    
+    private Point[] calcNormals(Polygon p, Point[] n) {
+        Point v = new Point();
+        for (int i = 0; i < p.nPoints; i++) {
+            int j = (i+1) % p.nPoints;
+            int k = (i+2) % p.nPoints;
+            // make vector be -1/mI + 1J
+            n[i].setX( -(p.v[j].getY() - p.v[i].getY()) / (p.v[j].getX() - p.v[i].getX()) );
+            n[i].setY(1.0);
+            
+            v.setX( p.v[k].getX() - p.v[i].getX() );
+            v.setY( p.v[k].getY() - p.v[i].getY() );
+            if (pointProduction(n[i], v) > 0) {
+                // inner normal 
+                n[i].setX(n[i].getX() * -1);
+                n[i].setY(n[i].getY() * -1);
+            }
+        }
+        return n;
+    }
+    
+    private double pointProduction(Point v1, Point v2) {
+        return v1.getX() * v2.getX() + v1.getY() * v2.getY();
+    }
+    
+    private double[] clipCyrusBeck(Point p1, Point p2, Point[] n) {
+        double t,num,den;
+        // vectors
+        Point dirV = new Point();
+        Point F = new Point();
+        
+        // start largest at smallest legal value and smallest 
+        // at largest legal value
+        double t1 = 0.0;
+        double t2 = 1.0;
+        // compute the direction vector
+        dirV.x = p2.x - p1.x;
+        dirV.y = p2.y - p1.y;
+        
+        boolean visible = true;
+        int i = 0;
+        while ((i < poly.nPoints) && visible) {
+            F.x = p1.x - poly.v[i].x;
+            F.y = p1.y - poly.v[i].y;
+            
+            num = pointProduction(n[i], F);
+            den =  pointProduction(n[i], dirV);
+            
+            // Parallel or Point
+            if (den == 0.0) {
+// parallel - if outside then forget the line; if inside then there are no 
+                // intersections with this side 
+                // but there may be with other edges, so in this case just keep going
+                if (num > 0.0) {
+                    //   Parallel and outside or point (p1 == p2) and outside
+                    visible = false;
+                }
+            } else {
+                t = -(num/den);
+                if (den < 0.0) {
+                    // entering
+                    if (t <= 1.0 && t > t1) t1 = t;
+                } else if ( t >= 0.0 && t < t2) t2 = t;
+            }
+            i++;
+        }
+        /*if (t1 <= t2) {
+            return new double[] {
+                p1.x + t1*dirV.x,
+                p1.y + t1*dirV.y,
+                p1.x + t2*dirV.x,
+                p1.y + t2*dirV.y
+            };
+        } else visible = false;*/
+        return new double[] {
+            p1.x + t1*dirV.x,
+            p1.y + t1*dirV.y,
+            p1.x + t2*dirV.x,
+            p1.y + t2*dirV.y
+        };
+    }
+    
+    private class Polygon {
+        int nPoints;
+        Point[] v;
+
+        public Polygon(Point[] points) {
+            this.v = points;
+            nPoints = points.length;
+        }
+    }
+}