The machinery of linear algebra can be used to express many of the operations required to arrange objects in a 3D scene, view them with cameras, and get them onto the screen.
可以像上述图片一样，利用一个矩阵乘法把一个2维向量转换为另一个2维向量，这种变换就叫做linear transformation.
表示的是坐标轴方向缩放的比例。
A shear is something that pushed things sideaways, producing something like a deck of cards across which you push your hand; the bottom card stays put and cards move more the closer they are to the top of the deck.
一个矩阵经过剪切会得到平行四边形，而一个圆形经过剪切会得到一个椭圆。
剪切还可以被看作是单个坐标轴的旋转。如：
可以看成是垂直坐标轴顺时针旋转角度ϕ。
可以看成是水平坐标轴逆时针旋转角度ϕ。