Here's a perspective projection matrix. Say you multiply a point with a
coordinate, 3,7,0,1 by this matrix. I'll save you the effort. You get 3, 7,
negative 2.2, 0. W is 0. If you try to divide negative 2 by 2 by 0 without
safety glasses on, the world ends. In fact for any point X, Y, 0, 1, we'll get
a W of 0. What do all of these points have in common? The points are exactly on
one of the faces of the frustum itself. The points are in the anti-frustum, a
mirrored frustum behind the camera. The points are on a plane parallel to the
near plane that goes through the origin. Or the points are behind the camera.
この透視投影行列と座標(3,7,0,1)を掛けるとします
計算すると(3,7,-2.2,0)になります
wはゼロになります -2を2と0で割るとワールドはなくなります
実際(x,y,0,1)どの点でもwはゼロになります
これらの点に共通することは？
点はすい台の面のどこかにある
点はカメラの後ろにある反転した すい台の上にある
原点を通る手前の面と平行な板の上にある
点はすべてカメラの後ろにある