void d3colorN (change, colors, nlevel, mesh) BOXFILL.C Level 2
 
float * change The array of z-values that will be used to determine the values of z where the colors change.
int *colors An array of color values or patterns to be used when shading a 3-D surface. The array will be used sequentially with the first color corresponding to the lowest level. The array must beat least  nlevel elements long.
nt nlevel The number of color changes that will take place from minimum z to maximum z.
int mesh A combination of bit flags with the following meanings:
= 0 for no mesh.
= DRAW_MESH if the 3-D mesh is to be seen. The color will be based on the average of a cell's corner values if no other flags are on.
= FILL_ON_CONTOURS if the color changes are to occur at z contour levels. No borders will be drawn on contour boundaries.
= COLOR_ON_X if the color changes are to be determined by the value of x. This will create bands of color in the y-direction.
= COLOR_ON_Y if the color changes are to be determined by the value of y. This will create bands of color in the x-direction.
 
d3colorN() causes a 3-D surface to be filled with the colors specified in colors. This routine allows you to specify nonlinear breakpoints between the different color levels. Otherwise, this routine behaves in the same way as d3colorL(). You may want to use ColorKeyN() to make a key for your plot