How can I colorize an imported model?

Question

How can I colorize an imported model from for example 3ds max?

I'm trying to find the way to colorize a 3D plot from an imported model with something like this:

ColorFunction -> Function[{x, y, z}, ColorData["GreenBrownTerrain"][z^2]]

But I don't know how. Thank you very much for your help.

Answer 1

Here I color the 747 model via the VertexColors option to GraphicsComplex.

jet = Import["ExampleData/747.3ds.gz"];
(* Function to change color of GraphicsComplex *)
newcolor[gcomplex_, colfun_] := Module[{
   pts = First@gcomplex,
   data = gcomplex[[2]],
   vcol},
  (* Remove old RGBColor stuff in data part of the graphics complex *)
  data = DeleteCases[data, RGBColor[_]]; 
  (* Introduce vertex colors according to colfun *)
  vcol = colfun /@ pts;
  (* Return a new GraphicsComplex with VertexColors *)
  GraphicsComplex[pts, data, VertexColors -> vcol]
  ]
(* Find range of z values *)
{zmin, zmax} = {Min@#, Max@#} &@(Last /@ 
 Flatten[Cases[jet, GraphicsComplex[__], Infinity][[All, 1]], 1]);
(* Color function that maps {x,y,z} to color *)
cf = ColorData["GreenBrownTerrain"][Rescale[Last@#, {zmin, zmax}]^2] &
(* Change all GraphicsComplex objects *)
jet /. gc_GraphicsComplex :> newcolor[gc, cf]

There are some visible artefacts in the coloring, but at least it's something.

Comment if there's some part you'd like me to explain further.

Here's the before/after for ExampleData[{"Geometry3D","Phobos"}]