从窗口到opengl坐标系的直观解释 [英] From window to opengl coordinate system intuitive explanation

问题描述

使用鼠标功能时，我试图理解从窗口坐标轴(左上角原点)到OpenGL坐标轴(左下角原点)的地图.在相关书籍中，此地图由以下两行描述:

I am trying to understand the map from window coordinate axis (origin top-left) to OpenGL coordinate axis (origin left-bottom) when using the mouse function. In relevant book this map is described by the two following lines:

points[count].x = (float) x / (w/2) - 1.0;
points[count].y = (float) (h-y) / (h/2) - 1.0;

我怀疑这两行描述了一个比例.您能对此地图进行直观的数学解释吗?

I suspect that these two lines depict a scale. Could you please give an intuitive-mathematical explanation of this map?

推荐答案

您指的是哪本书? NDC空间中的原点是视口的中心( 0,0 是中心； -1，-1 是左下角； 1， 1 是右上角).其他任何坐标空间都由投影矩阵定义.

What book are you referring to? The origin in NDC-space is the center of the viewport (0,0 is the center; -1,-1 is the bottom-left; 1,1 is the top-right). Any other coordinate space is defined by your projection matrix.

我相信这本书试图教给你的是 NDC _-1，-1 是视口和 NDC _1,1 是右上角.

I believe what the book is trying to teach you is that NDC_-1,-1 is the bottom-left corner of your viewport and NDC_1,1 is the top-right corner.

• NDC _X =(2.0 *(Screen _X -Viewport _X )/Viewport _W )-1.0;

• NDC_X = (2.0 * (Screen_X - Viewport_X) / Viewport_W) - 1.0;

NDC _Y =(2.0 *(Screen _Y -Viewport _Y )/Viewport _H )-1.0;

NDC_Y = (2.0 * (Screen_Y - Viewport_Y) / Viewport_H) - 1.0;

  

  

当然，您还需要执行一个附加步骤，因为Y轴在鼠标坐标系中沿相反的方向运行.这就是为什么您在映射h-y

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