在OpenGL中调整大小时保持宽高比

问题描述

我实现了以下代码:

void TestGlPlot::resizeGL(int width, int height)
{
   setupViewport(width, height);
}

void TestGlPlot::setupViewport(int width, int height)
{
   /* Prevent divide by zero --------------------------------------------------------------------*/
   if (height == 0) height = 1;
   /* Calculate aspect ratio --------------------------------------------------------------------*/
   float aspectRatio = (float)width / (float)height;

   /* Set viewport to cover the window ----------------------------------------------------------*/
   glViewport(0, 0, width, height);

   /* Set aspect ratio --------------------------------------------------------------------------*/
   glMatrixMode(GL_PROJECTION); /* switch to projection matrix */
   glLoadIdentity();
   /*
   if (width >= height)
   {
   gluOrtho2D(-0.5*aspectRatio, 0.5*aspectRatio, 0.0, 1.0);
   }
   else
   {
   gluOrtho2D(-0.5, 0.5, 0.0*aspectRatio, 1.0*aspectRatio);
   }
   glMatrixMode(GL_MODELVIEW);
   */
   gluOrtho2D(-1, 1, 0.0, 1.0);
   glMatrixMode(GL_MODELVIEW);
}

void TestGlPlot::paintEvent(QPaintEvent *event) {
   makeCurrent();
   setupViewport(width(), height());

   glMatrixMode(GL_MODELVIEW);

   /* Set white background ----------------------------------------------------------------------*/
   glClear(GL_COLOR_BUFFER_BIT);
   glClearColor(255,255,255,0);

   /* Paint OpenGL events -----------------------------------------------------------------------*/
   glColor4f(1.0, 0.0, 0.0, 1.0);

   /* light grey */
   glColor4f(0.0, 0.0, 0.0, 0.3);
   gluPartialDisk(plainQuad, 0.1, 1, 20, 4, -60, 120);

   /* Paint QPainter events ---------------------------------------------------------------------*/
   QPainter painter(this);

   /* Draw grey border around plot --------------------------------------------------------------*/
   painter.setPen(QColor("#808080"));
   painter.drawRect(0, 0, width()-1, height()-1);

   painter.setFont(font);

   /* Translate coordinate system to (0,0) center -----------------------------------------------*/
   QMatrix m;
   m.translate(width()*0.5, height()*0.5);
   painter.setMatrix(m);

   /* Left side descriptions for radius ---------------------------------------------------------*/
   painter.drawText(-0.17*width(), 0.38*height(), tr("100m"));
   painter.drawText(-0.27*width(), 0.28*height(), tr("200m"));
   painter.drawText(-0.37*width(), 0.18*height(), tr("300m"));
   painter.drawText(-0.47*width(), 0.08*height(), tr("400m"));

   painter.drawText(0.45*width(), -0.01*height(), tr("60°"));
   painter.drawText(0.26*width(), -0.38*height(), tr("30°"));

   painter.drawText(-0.47*width(), -0.01*height(), tr("300°"));
   painter.drawText(-0.28*width(), -0.38*height(), tr("330°"));

   painter.end();
}

我尝试了其他方法来调整大小(保持partialDisk对象的形状而不拉伸它)，但是每种方法都失败了.我还想保留单位圆的坐标处理(这样我就可以将我的测量规格化并将其绘制到极坐标图中).

i tried different methods for resize handling (keeping the shape of the partialDisk object without stretching it) but every method failed. I also want to keep the coordinate handling of the unit-circle (so i can normalize my measurements and draw them into a polar-plot).

推荐答案

要保持长宽比，通常可以选择以下几种方式:

To keep the aspect ratio, you have several options in general:

1. 始终缩放到一维.例如，您仅定义要始终看到水平范围[-0.5,0.5].在这种情况下，您必须通过系数(1/aspect_viewport)校正垂直范围.
2. 使用一些等效的信箱.因此，您定义了一个始终希望完全看到的感兴趣区域"，但是您可能会看到更多的宽度或高度，具体取决于窗口的纵横比(在观看带信箱的电影时，这基本上等同于黑条).有两种情况需要考虑:视口的纵横比区域的纵横比大，因此视域的纵横比更大.在这种情况下，您应该绘制完整高度并将水平范围扩大(aspect_viewport/aspect_region).否则，窗口的外观将低于您所在区域的外观，因此您应使用完整宽度并按(aspect_region/aspect_viewport)放大垂直范围.请注意，在两种情况下，该因子均为> = 1.

在您的代码中，您几乎实现了方法2，但是您获得了AspectRatio< 1例错误，应该是

In your code, you almost have implemented method 2, but you got the aspectRatio < 1 case wrong, it should be

   if (width >= height)
           gluOrtho2D(-0.5f*aspectRatio, 0.5f*aspectRatio, 0.0f, 1.0f);
   else
           gluOrtho2D(-0.5f, 0.5f, 0.0, 1.0/aspectRatio);

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