Camera Position

The three basic camera properties are its position, the direction in which it is pointing, and its orientation. The keywords for specifying these values are described below. The default values are designed to provide a reasonable view of a sphere of radius 2 located at origin. If these default values are used, the origin is projected onto the center of the image plane, with the world x axis running left-to-right, the z axis bottom-to-top, and the y axis going ``into'' the screen.

$\begin{defkey}{eyep}{\evec{pos}} Place the virtual camera at the given position. \end{defkey}$
The default camera position is (0, -8, 0).

$\begin{defkey}{lookp}{\evec{pos}} Point the virtual camera toward the given position. \end{defkey}$
The default look point is the origin (0, 0, 0). The look point and camera position must not be coincident.

$\begin{defkey}{up}{\evec{direction}} The \lq\lq up'' vector from the camera point is set to the given direction. \end{defkey}$
This up vector need not be orthogonal to the view vector, nor need it be normalized. The default up direction is (0, 0, 1).

Another popular standard viewing geometry, with the x axis running left-to-right, the y axis bottom-to-top, and the z axis pointing out of the screen, may be obtained by setting the up vector to (0, 1, 0) and by placing the camera on the positive z axis.