From ab008b050fa7f56f1273b1b3dd3e16d4dcff5902 Mon Sep 17 00:00:00 2001
From: James Turk <james.p.turk@gmail.com>
Date: Tue, 23 Aug 2005 21:55:03 +0000
Subject: [PATCH] Pen circle drawing revisited

---
 CHANGELOG.txt         |  4 ++-
 include/video/Pen.hpp |  5 ++-
 src/video/Pen.cpp     | 78 ++++++++++++-------------------------------
 3 files changed, 28 insertions(+), 59 deletions(-)

diff --git a/CHANGELOG.txt b/CHANGELOG.txt
index 32659c8..320412a 100644
--- a/CHANGELOG.txt
+++ b/CHANGELOG.txt
@@ -1,10 +1,12 @@
 Changelog for Photon
-$Id: CHANGELOG.txt,v 1.11 2005/08/18 07:05:34 cozman Exp $
+$Id: CHANGELOG.txt,v 1.12 2005/08/23 21:55:03 cozman Exp $
 
 ! : Major Changes   (potentially breaking existing code)
 + : New Features   
 * : Minor Changes   (bugfixes and behind-the-scenes changes)
 
+0.1.0
+    * Rewrote circle drawing code in Pen, major speed up.
 
 0.0.2 - Released 2005-18-08
     ! Removed InputListener, opting to move features into State class.
diff --git a/include/video/Pen.hpp b/include/video/Pen.hpp
index aee11a4..1707702 100644
--- a/include/video/Pen.hpp
+++ b/include/video/Pen.hpp
@@ -5,7 +5,7 @@
 //  James Turk (jpt2433@rit.edu)
 //
 // Version:
-//  $Id: Pen.hpp,v 1.3 2005/07/20 03:58:54 cozman Exp $
+//  $Id: Pen.hpp,v 1.4 2005/08/23 21:55:03 cozman Exp $
 
 #ifndef PHOTON_VIDEO_PEN_HPP
 #define PHOTON_VIDEO_PEN_HPP
@@ -134,6 +134,9 @@ public:
 // data members
 private:
     Color color_;
+    
+    // 30 seems to be an even tradeoff between speed and roundness
+    static const int CIRCLE_RESOLUTION = 30;    
 };
 
 }
diff --git a/src/video/Pen.cpp b/src/video/Pen.cpp
index ded5063..2a20ebb 100644
--- a/src/video/Pen.cpp
+++ b/src/video/Pen.cpp
@@ -5,7 +5,7 @@
 //  James Turk (jpt2433@rit.edu)
 //
 // Version:
-//  $Id: Pen.cpp,v 1.5 2005/07/20 03:58:54 cozman Exp $
+//  $Id: Pen.cpp,v 1.6 2005/08/23 21:55:03 cozman Exp $
 
 #include "video/Pen.hpp"
 
@@ -125,39 +125,21 @@ void Pen::fillRect(const math::Rect &rect) const
 
 void Pen::drawCircle(const math::Circle &circle) const
 {
-    //written from Bresenham's circle algorithm
-    double cx(circle.getCenter().x);
-    double cy(circle.getCenter().y);
-    double d(3-(2*circle.getRadius()));
-    double x(0);
-    double y(circle.getRadius());
-
+    scalar radius(circle.getRadius());
+    scalar cx(circle.getCenter().x);
+    scalar cy(circle.getCenter().y);
+    scalar angle(0);
+    const scalar angleStep(2*math::PI/CIRCLE_RESOLUTION);
+    
     glBindTexture(GL_TEXTURE_2D,0);
     glPushAttrib(GL_CURRENT_BIT);
     color_.makeGLColor();
     
-    glBegin(GL_POINTS); // draw points, creating a circle
-    while(y > x)
+    glBegin(GL_LINE_LOOP);
+    for(int i=0; i<CIRCLE_RESOLUTION; ++i)
     {
-        glVertex2d(cx+x,cy+y);
-        glVertex2d(cx+x,cy-y);
-        glVertex2d(cx-x,cy+y);
-        glVertex2d(cx-x,cy-y);
-        glVertex2d(cx+y,cy+x);
-        glVertex2d(cx+y,cy-x);
-        glVertex2d(cx-y,cy+x);
-        glVertex2d(cx-y,cy-x);
-
-        if(d < 0)
-        {
-            d += x*4 + 6;
-        }
-        else
-        {
-            d += (x-y)*4 + 10;
-            --y;
-        }
-        ++x;
+        glVertex2f(cx+radius*std::cos(angle), cy+radius*std::sin(angle));
+        angle += angleStep;
     }
     glEnd();
     glPopAttrib();
@@ -165,39 +147,21 @@ void Pen::drawCircle(const math::Circle &circle) const
 
 void Pen::fillCircle(const math::Circle &circle) const
 {
-    //written from Bresenham's circle algorithm
-    double cx(circle.getCenter().x);
-    double cy(circle.getCenter().y);
-    double d(3-(2*circle.getRadius()));
-    double x(0);
-    double y(circle.getRadius());
+    scalar radius(circle.getRadius());
+    scalar cx(circle.getCenter().x);
+    scalar cy(circle.getCenter().y);
+    scalar angle(0);
+    const scalar angleStep(2*math::PI/CIRCLE_RESOLUTION);
 
     glBindTexture(GL_TEXTURE_2D,0);
     glPushAttrib(GL_CURRENT_BIT);
     color_.makeGLColor();
-
-    glBegin(GL_LINES);  // draw lines instead of points, filling the circle
-    while(y > x)
+    
+    glBegin(GL_POLYGON);
+    for(int i=0; i<CIRCLE_RESOLUTION; ++i)
     {
-        glVertex2d(cx+x,cy+y);
-        glVertex2d(cx+x,cy-y);
-        glVertex2d(cx-x,cy-y);
-        glVertex2d(cx-x,cy+y);
-        glVertex2d(cx+y,cy+x);
-        glVertex2d(cx-y,cy+x);
-        glVertex2d(cx-y,cy-x);
-        glVertex2d(cx+y,cy-x);
-
-        if(d < 0)
-        {
-            d += x*4 + 6;
-        }
-        else
-        {
-            d += (x-y)*4 + 10;
-            --y;
-        }
-        ++x;
+        glVertex2f(cx+radius*std::cos(angle), cy+radius*std::sin(angle));
+        angle += angleStep;
     }
     glEnd();
     glPopAttrib();