中点算法绘制椭圆_程序
1. 中点算法绘制椭圆
由于算法特殊性，程序限制绘制第一象限部分；
1 void CCGProjectWorkView::midPoint_1P4Ellipse(int radiumA, int radiumB, const float lineColor[]) 2 { 3 int pointX, pointY; 4 float jugeFactorUp, jugeFactorDown; 5 pointX = 0; 6 pointY = radiumB; 7 8 glColor3f(lineColor[0], lineColor[1], lineColor[2]); 9 glBegin(GL_POINTS); 10 11 jugeFactorUp = radiumB*radiumB + radiumA*radiumA*(-radiumB + 0.25); 12 glVertex3f(pointX, pointY, 0); 13 while (radiumB*radiumB*(pointX+1) < radiumA*radiumA*(pointY-0.5)) 14 { 15 if (jugeFactorUp < 0)//中点在内部，正右方点H 16 { 17 jugeFactorUp += radiumB*radiumB*(2*pointX + 3); 18 pointX++; 19 } 20 else 21 { 22 jugeFactorUp += (radiumB*radiumB*(2*pointX + 3) + radiumA*radiumA*(-2*pointY + 2)); 23 pointY--; 24 pointX++; 25 } 26 glVertex3f(pointX, pointY, 0); 27 } 28 29 jugeFactorDown = sqrt(radiumB*(pointX + 0.5)) + radiumA*(pointY - 1) - radiumA*radiumB; 30 while(pointY > 0) 31 { 32 if (jugeFactorDown < 0)//在圆内，取D 33 { 34 jugeFactorDown += radiumB*radiumB*(2*pointX + 2) + radiumA*radiumA*(-2*pointY + 3); 35 pointX++; 36 pointY--; 37 } 38 else 39 { 40 jugeFactorDown += radiumA*radiumA*(-2*pointY +3); 41 pointY--; 42 } 43 glVertex3f(pointX, pointY, 0); 44 } 45 46 glEnd(); 47 48 }