Line/Rect collision fix

CodeExamples/LineRect/LineRect.pde

@@ -46,6 +46,12 @@ void draw() {
 
 // LINE/RECTANGLE
 boolean lineRect(float x1, float y1, float x2, float y2, float rx, float ry, float rw, float rh) {
+
+  // is either end INSIDE the rectangle?
+  // if so, return true immediately
+  boolean inside1 = pointRect(x1,y1, rx,ry,rw,rh);
+  boolean inside2 = pointRect(x2,y2, rx,ry,rw,rh);
+  if (inside1 || inside2) return true;
 
   // check if the line has hit any of the rectangle's sides
   // uses the Line/Line function below
@@ -62,6 +68,20 @@ boolean lineRect(float x1, float y1, float x2, float y2, float rx, float ry, flo
 }
 
 
+// POINT/RECTANGLE
+boolean pointRect(float px, float py, float rx, float ry, float rw, float rh) {
+
+  // is the point inside the rectangle's bounds?
+  if (px >= rx &&        // right of the left edge AND
+      px <= rx + rw &&   // left of the right edge AND
+      py >= ry &&        // below the top AND
+      py <= ry + rh) {   // above the bottom 
+        return true;
+  }
+  return false;
+}
+
+
 // LINE/LINE
 boolean lineLine(float x1, float y1, float x2, float y2, float x3, float y3, float x4, float y4) {
 

CodeExamples/LineRect/web-export/LineRect.pde

@@ -48,6 +48,12 @@ void draw() {
 
 // LINE/RECTANGLE
 boolean lineRect(float x1, float y1, float x2, float y2, float rx, float ry, float rw, float rh) {
+
+  // is either end INSIDE the rectangle?
+  // if so, return true immediately
+  boolean inside1 = pointRect(x1,y1, rx,ry,rw,rh);
+  boolean inside2 = pointRect(x2,y2, rx,ry,rw,rh);
+  if (inside1 || inside2) return true;
 
   // check if the line has hit any of the rectangle's sides
   // uses the Line/Line function below
@@ -64,6 +70,20 @@ boolean lineRect(float x1, float y1, float x2, float y2, float rx, float ry, flo
 }
 
 
+// POINT/RECTANGLE
+boolean pointRect(float px, float py, float rx, float ry, float rw, float rh) {
+
+  // is the point inside the rectangle's bounds?
+  if (px >= rx &&        // right of the left edge AND
+      px <= rx + rw &&   // left of the right edge AND
+      py >= ry &&        // below the top AND
+      py <= ry + rh) {   // above the bottom 
+        return true;
+  }
+  return false;
+}
+
+
 // LINE/LINE
 boolean lineLine(float x1, float y1, float x2, float y2, float x3, float y3, float x4, float y4) {
 
@@ -87,4 +107,3 @@ boolean lineLine(float x1, float y1, float x2, float y2, float x3, float y3, flo
 }
 
 
-

Website/line-rect.php

@@ -2,9 +2,16 @@
 
 <h1>LINE/RECTANGLE</h1>
 
-<p>We've actually already covered how to check if a line has hit a rectangle: it's really just four <a href="line-line.php">Line/Line</a> collisions, one for each side!</p>
+<p>We've actually already covered how to check if a line has hit a rectangle: it's really just two <a href="point-rect.php">Point/Rect</a> and four <a href="line-line.php">Line/Line</a> collisions, one for each side!</p>
 
-<p>For example, the left edge of the square starts at <code>(rx,ry)</code> and extends down to <code>ry+rh</code>. We can treat that as a line, using the algorithm we made in the last section:</p>
+<p>First, let's test if either of the ends of the line are inside the square. This is likely to happen if the line is much smaller than the square. To do this, we can use <a href="point-rect.php">Point/Rect</a> from the beginning of the book. If either end is inside, return <code>true</code> immediately and skip the rest.</p>
+
+<pre>boolean inside1 = pointRect(x1,y1, rx,ry,rw,rh);
+boolean inside2 = pointRect(x2,y2, rx,ry,rw,rh);
+if (inside1 || inside2) return true;
+</pre>
+
+<p>Next, we check for collision between the line and any edge of the square. For example, the left edge of the square starts at <code>(rx,ry)</code> and extends down to <code>ry+rh</code>. We can treat that as a line, using the algorithm we made in the last section:</p>
 
 <pre>boolean left =   lineLine(x1,y1,x2,y2, rx,ry, rx,ry+rh);
 </pre>