.sp
.LP
These routines treat the pixels in an image as elevations and perform
operations on the surface that is specified by these elevations.
.SH
SHORT DESCRIPTION OF ROUTINES
.IP "Normals and Angles -" 20
Compute the normal vector and angle with respect to the reference plane.
.IP "Slopes and Aspects -" 20
Calculate the slopes and aspects for elevation data.
.IP "Compute Cost -" 20
Find the distances along a surface from a reference pixel to all other
pixels in the image.
.IP "Find Tilt -" 20
Compute the best-fit plane parameters for the input VIFF file.
.IP "Remove Tilt -" 20
Remove an illumination gradient from an image by subtracting a
best-fit plane.
.IP "Add Tilt -" 20
Add a specified plane to the input image to correct for a tilt
in the image luminance.
.IP "Interactive Render -" 20
Interactively drape imagery over elevation data.
