我正在尝试将从书籍“使用OpenGL进行计算机图形学”中获取的标准顺时针椭圆中点算法转换为逆时针算法,从区域2开始运行。我让它工作并绘制了一个椭圆,但它与原始算法绘制的不完全相同,因此我认为我的代码中有一个小错误,但我似乎找不到,请有人帮帮忙吗?
这是原始算法:
这是我的版本:
我真的很感激能够帮我找到我做错了什么。
这是原始算法:
void ellipseMidpoint(int xCenter, int yCenter, int Rx, int Ry)
{
int Rx2 = Rx * Rx;
int Ry2 = Ry * Ry;
int twoRx2 = 2 * Rx2;
int twoRy2 = 2 * Ry2;
int p;
int x = 0;
int y = Ry;
int px = 0;
int py = twoRx2 * y;
void ellipsePlotPoints(int, int, int, int);
/* Plot the initial point in each quadrant. */
ellipsePlotPoints(xCenter, yCenter, x, y);
/* Region 1 */
p = round(Ry2 - (Rx2 * Ry) + (0.25 * Rx2));
while (px < py) {
x++;
px += twoRy2;
if (p < 0)
p += Ry2 + px;
else {
y--;
py -= twoRx2;
p += Ry2 + px - py;
}
ellipsePlotPoints(xCenter, yCenter, x, y);
}
/* Region 2 */
p = round(Ry2 * (x + 0.5) * (x + 0.5) + Rx2 * (y - 1) * (y - 1) - Rx2 * Ry2);
while (y > 0) {
y--;
py -= twoRx2;
if (p > 0)
p += Rx2 - py;
else {
x++;
px += twoRy2;
p += Rx2 - py + px;
}
ellipsePlotPoints(xCenter, yCenter, x, y);
}
}
void ellipsePlotPoints(int xCenter, int yCenter, int x, int y)
{
setPixel(xCenter + x, yCenter + y);
setPixel(xCenter - x, yCenter + y);
setPixel(xCenter + x, yCenter - y);
setPixel(xCenter - x, yCenter - y);
}
这是我的版本:
void ellipseMidpointCounterClockwise(int xCenter, int yCenter, int Rx, int Ry)
{
int Rx2 = Rx * Rx;
int Ry2 = Ry * Ry;
int twoRx2 = 2 * Rx2;
int twoRy2 = 2 * Ry2;
int p;
int x = Rx;
int y = 0;
int px = twoRy2 * x;
int py = 0;
void ellipsePlotPoints(int, int, int, int);
/* Plot the initial point in each quadrant. */
ellipsePlotPoints(xCenter, yCenter, x, y);
/* Region 2 */
p = round(Ry2 * (x - 0.5) * (x - 0.5) + Rx2 * (y + 1) * (y + 1) - Rx2 * Ry2);
while (py < px) {
y++;
py += twoRx2;
if (p > 0)
p += Rx2 - py;
else {
x--;
px -= twoRy2;
p += Rx2 - py + px;
}
ellipsePlotPoints(xCenter, yCenter, x, y);
}
/* Region 1 */
p = round(Ry2 * (x - 1.0) * (x - 1.0) + Rx2 * (y + 0.5) * (y + 0.5) - Rx2 * Ry2);
while (x > 0) {
x--;
px -= twoRy2;
if (p < 0)
p += Ry2 + px;
else {
y++;
py += twoRx2;
p += Ry2 + px - py;
}
ellipsePlotPoints(xCenter, yCenter, x, y);
}
}
我真的很感激能够帮我找到我做错了什么。