You can use bitmap image as input information to control geometries by IImageMap class. You can extract a value out of an image at a specific u-v location with get(double,double) method. The first argument is u location ranging from 0.0 to 1.0, the second is v, and it returns a value ranging from 0.0 to 1.0 which means a gray scale value (black is 0.0 and white is 1.0). IImageMap can read images in JPEG, PNG and GIF formats. The input bitmap file should be stored in the "data" folder inside the Processing sketch folder in the same way as you store a 3D data file to import.

The sample input file used in the example is below.

surface6.3dm

The input bitmap used in the example is this.

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface6.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map1.jpg");

for (ISurface surf : surfaces) {
  int unum = 50, vnum = 50;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt1 = surf.pt( i*uinc, j*vinc );
      IVec pt2 = surf.pt( i*uinc, j*vinc, val*-10 );
      new ICurve(pt1, pt2).clr(0);
    }
  }
}

Here is an example to differentiate offset depths of a vertex of panel.
The sample input file used in the example is below.

surface7.3dm

The input bitmap used in the example is this.

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface7.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map1.jpg");

for (ISurface surf : surfaces) {
  int unum = 20, vnum = 20;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt11 = surf.pt( i*uinc, j*vinc );
      IVec pt21 = surf.pt( (i+1)*uinc, j*vinc );
      IVec pt12 = surf.pt( i*uinc, (j+1)*vinc, val*-4 );
      IVec pt22 = surf.pt( (i+1)*uinc, (j+1)*vinc );
      new ISurface(pt11, pt12, pt22, pt21).clr(.3);
    }
  }
  surf.del();
}

Here is an example to control the width of panel by changing sampling location of the input surface with the image value. The code below is control the width in v direction.

Here is the input bitmap used in the example.

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface7.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map1.jpg");

for (ISurface surf : surfaces) {
  int unum = 20, vnum = 20;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt11 = surf.pt( i*uinc, j*vinc );
      IVec pt21 = surf.pt( (i+1)*uinc, j*vinc );
      IVec pt12 = surf.pt( i*uinc, (j + val)*vinc );
      IVec pt22 = surf.pt( (i+1)*uinc, (j + val)*vinc );
      new ISurface(pt11, pt12, pt22, pt21).clr(.3);
    }
  }
  surf.del();
}

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface7.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map1.jpg");

for (ISurface surf : surfaces) {
  int unum = 20, vnum = 20;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt11 = surf.pt( i*uinc, j*vinc );
      IVec pt21 = surf.pt( (i + val)*uinc, j*vinc );
      IVec pt12 = surf.pt( i*uinc, (j + 1)*vinc );
      IVec pt22 = surf.pt( (i + val )*uinc, (j + 1)*vinc );
      new ISurface(pt11, pt12, pt22, pt21).clr(.3);
    }
  }
  surf.del();
}

Here is an example to rotate panelized surfaces by sampled values of the image. The input bitmap used in the example is this.

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface7.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map1.jpg");

for (ISurface surf : surfaces) {
  int unum = 20, vnum = 20;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt11 = surf.pt( i*uinc, j*vinc );
      IVec pt21 = surf.pt( (i + 1)*uinc, j*vinc );
      IVec pt12 = surf.pt( i*uinc, (j + (1-val) )*vinc );
      IVec pt22 = surf.pt( (i + 1)*uinc, (j + (1-val) )*vinc );
      ISurface panel = new ISurface(pt11, pt12, pt22, pt21).clr(.2);
      
      IVec center = surf.pt( (i+0.5)*uinc, (j+0.5)*vinc );
      IVec normal = surf.nml( (i+0.5)*uinc, (j+0.5)*vinc );
      panel.rot(center, normal, val*PI/4 );
    }
  }
  surf.del();
}

Here is an example to scale panelized surfaces by sampled values of the image. The input bitmap used in the example is this.

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface7.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map1.jpg");

for (ISurface surf : surfaces) {
  int unum = 40, vnum = 40;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt11 = surf.pt( i*uinc, j*vinc );
      IVec pt21 = surf.pt( (i + 1)*uinc, j*vinc );
      IVec pt12 = surf.pt( i*uinc, (j + 1)*vinc );
      IVec pt22 = surf.pt( (i + 1)*uinc, (j + 1)*vinc );
      ISurface panel = new ISurface(pt11, pt12, pt22, pt21).clr(.2);
      
      IVec center = surf.pt( (i+0.5)*uinc, (j+0.5)*vinc );
      // val is inverted by subtraction
      panel.scale(center, 1 - val );
    }
  }
  surf.del();
}

Here is an example to use color of the image with the clr() method of IImageMap class. When the image is full color image, the value returned by get() method is a gray scale value when the color is converted into gray.

The input bitmap used in the example is this.

import processing.opengl.*;
import igeo.*;

size(480, 360, IG.GL);

IG.open("surface7.3dm");
ISurface[] surfaces = IG.surfaces();

IImageMap map = new IImageMap("map2.jpg");

for (ISurface surf : surfaces) {
  int unum = 40, vnum = 40;
  double uinc = 1.0/unum, vinc = 1.0/vnum;

  for (int i=0; i < unum; i++) {
    for (int j=0; j < vnum; j++) {
      double val = map.get( i*uinc, j*vinc );

      IVec pt11 = surf.pt( i*uinc, j*vinc );
      IVec pt21 = surf.pt( (i + 1)*uinc, j*vinc );
      IVec pt12 = surf.pt( i*uinc, (j + 1)*vinc, val*-4 );
      IVec pt22 = surf.pt( (i + 1)*uinc, (j + 1)*vinc );
      ISurface panel = new ISurface(pt11, pt12, pt22, pt21);

      panel.clr(map.clr( i*uinc, j*vinc ));
    }
  }
  surf.del();
}