vectorsurf.pro is a preserved example for plotting irregularly spaced 3-D data by interpolating onto a grid and then rendering a shaded surface.

Download raw vectorsurf.pro.

IDL> x = [4,6,1,7,1,8,5,2,4]
IDL> y = [3,3,1,6,4,5,6,8,1]
IDL> z = sqrt((x-3)^2+(y-2)^2)+randomn(seed)+2
IDL> vectorsurf, x, y, z

zz = MIN_CURVE_SURF(z, x, y, Nx=points, Ny=points)
SHADE_SURF, zz, xx, yy, XSTYLE=1, YSTYLE=1, ZSTYLE=1
SURFACE, zz, xx, yy, /NODATA, /NOERASE, /SAVE