The following example shows panelization with random length panels. Each of the panel length is defined by vlen .
The sample input file used in the example is below.

surface5.3dm

add_library('igeo')

size(480, 360, IG.GL)

IG.open("surface5.3dm")
surfaces = IG.surfaces()

for surf in surfaces :
    unum = 30
    vnum = 40
    uinc = 1.0/unum
    vinc = 1.0/vnum
    for i in range(unum) : 
        for j in range(vnum) :
            vlen = IRand.getInt(1, 10)
            if j+vlen > vnum : 
                vlen = vnum-j
            cpts = []
            cpts.append([])
            cpts.append([])
            for k in range(vlen+1) : 
                cpts[0].append(surf.pt(i*uinc, (j + k)*vinc))
                cpts[1].append(surf.pt((i+1)*uinc, (j + k)*vinc))
            ISurface(cpts).clr(IRand.clr())
            j += vlen-1
    surf.del()

And then the offset distance of the panel from the orignal input surface is randomized by the parameter depth.

add_library('igeo')

size(480, 360, IG.GL)

IG.open("surface5.3dm")
surfaces = IG.surfaces()

for surf in surfaces :
    unum = 30
    vnum = 40
    uinc = 1.0/unum
    vinc = 1.0/vnum
    for i in range(unum) :
        for j in range(vnum) :
            vlen = IRand.getInt(1, 10)
            if j+vlen > vnum :
                vlen = vnum-j
            cpts = []
            cpts.append([])
            cpts.append([])
            depth = IRand.get(0, 1)
            for k in range(vlen+1) : 
                cpts[0].append(surf.pt(i*uinc, (j+k)*vinc, depth))
                cpts[1].append(surf.pt((i+1)*uinc, (j+k)*vinc, depth))
            ISurface(cpts).clr(IRandom.gray())
            j += vlen-1
    surf.del()