Defined in utility.web .
This function is used for the figure in The Perspective Projection, illustrating a perspective projection as it could be done
by hand. It draws a rectangle in the ground plane and the construction
lines used for putting it into perspective. It also labels the
vanishing and measuring points.
The arguments:
const real front_corner_x
 The xcoordinate of the front corner of the rectangle.
const real front_corner_z
 The zcoordinate of the front corner of the rectangle.
const real side_lft
 The length of the left side of the rectangle.
const real side_rt
 The length of the right side of the rectangle.
const real angle_rt
 The angle at which the right side of the rectangle recedes to the
horizon.
const real f_2_cv
 The distance from the focus to the center of vision.
const real gl_2_cv
 The distance of the ground line to the center of vision.
const real horizon_lft
 Default: 6.
The length of the horizon line leftwards of the center of vision.
real horizon_rt
 Default: 0.
The length of the horizon line rightwards of the center of vision.
real gl_lft
 Default: 0.
The length of the ground line leftwards of the line from the focus to
the center of vision.
real gl_rt
 Default: 0.
The length of the ground line rightwards of the line from the focus to
the center of vision.
Example:
persp_0(3, 2, 10, 5, 47.5, 7, 5, 8.5, 9.5, 8.5, 9.5);
Fig. 199.
