What is view transformation ?
- Think about how to take a photo
- find a good place and arrange people (model transformation)
- find a good angle to put the camera (view transformation)
- cheese! (projection transformation)
Define the camera
- Position
- Look-at direction
- Up direction
keep the camera at (0,0,0) and up direction is axis Y, look-at direction is axis -Z
$M_{view}$ in math ?
$M_{view} = R_{view}T_{view}$
Translate Matrix $T_{view}$: first move point to origin
Rotate Matrix $R_{view}$: Rotate $R_{z}$ to $-Z$, $R_{y}$ to $Y$, $R_{z} \times R_{y}$ to $X$. Consider its inverse rotation: $M^{-1}{rotate} = M^{T}{rotate}$
so $R_{view}$ is: