在看了https://www.scratchapixel.com/lessons/3d-basic-rendering/ray-tracing-generating-camera-rays/generating-camera-rays
这个教程后，对其中的可视角相关的结论有一些疑问，文中提到“We can therefore multiply the screen pixel coordinates (which at the moment are contained in the range [-1, 1]) by this number to scale them up or down. As you may have guessed, this operation changes how much of the scene we see, and is equivalent to zooming in (we see less of the scene when the field of view decreases) and out (and see more of the scene when the value of the field of view increases).”，大意是可视角的增加和减小可以类比于画面的缩小或放大。有点不理解为什么可视角增大了，物体变得更“远”了呢？摄像机不是应该放在世界坐标的(0,0,0)么？画布的中心也应该在(0,0,-1)吧？增大或缩小可视角难道不是只对x和y坐标做缩放么？