You can set the contents of a Coordinate node via the implied set_point eventIn of the point exposedField. You can do this type of operation with all exposedFields.

As an instructive example let's look at Evgeny Demidov's Globe PROTO. This PROTO is a customized version of a sphere. The PROTO takes a value which is effectively the smoothness of the sphere and an URL of a texture for arguments. You can find the PROTO at: http://www.ipm.sci-nnov.ru/~DEMIDOV/VRML/Globe/Globe.htm

I've added some comments in the text of the PROTO below:

#VRML V2.0 utf8   Globe PROTO,  Evgeny Demidov,  9 Dec 2000

NavigationInfo{ type "EXAMINE" }
Background{ skyColor .5 .5 1}

PROTO Globe[
 field MFString urlImg ""
#by default n the stepping factor is 30
 field SFInt32  n      30 
]{
Transform{ scale 2 2 2 
 children[
 Shape{ appearance
  Appearance{ material Material{ diffuseColor 1 1 1}
   texture ImageTexture { url IS urlImg}}
  geometry DEF scrIFS IndexedFaceSet{ coord DEF scrCoord Coordinate{}
   texCoord DEF scrTC TextureCoordinate{}
   creaseAngle 2}}]
}

DEF INIT Script{
#TC is for texture coordinates
  field SFNode scrTC  USE scrTC
  field SFNode scrIFS USE scrIFS
  field SFNode scrCoord  USE scrCoord
  field SFInt32 n IS n
  directOutput TRUE
url ["javascript:
function initialize() { 
  n1=n+1;
  stepTh=3.142/(n-1); stepFi=6.2832/n;
  var k=0, i,j;
  var p = new MFVec3f();  p.length = n*n;
#compute the quadralaterals that will make up the sphere
  for (j= 0; j< n; j++)
    for (i= 0; i< n; i++) {
      fi=i*stepFi;   theta=j*stepTh;
      t=Math.sin(theta);
      p[k].x=t*Math.sin(fi);
      p[k].y=-Math.cos(theta);
      p[k++].z=t*Math.cos(fi); 
	  }
  scrCoord.set_point = p;
  
  var c = new MFInt32( );  c.length = 5*(n-1)*n;
  k=0;
  for (j= 0; j< n-1; j++){
   for (i= 0; i< n-1; i++){
    c[k++]=i+n*j; c[k++]=i+n*j+1; c[k++]=i+n*j+n+1; c[k++]=i+n*j+n; c[k++]=-1;
	}
   c[k++]=n*j+n-1; c[k++]=n*j; c[k++]=n*j+n; c[k++]=n*j+n+n-1; c[k++]=-1;
  }
  scrIFS.set_coordIndex = c;

#computer the texture coordinates
  var pt = new MFVec2f();  pt.length = n*n1;

  k=0;  var sti=1.0/n, stj=1/(n-1);

  for (j= 0; j< n; j++)
    for (i= 0; i< n1; i++) {
      pt[k].x=i*sti;

      pt[k++].y=j*stj;}

  scrTC.set_point = pt;

//print( pt );
  var ti = new MFInt32( );  ti.length = 5*(n-1)*n;
  k=0;
  for (j= 0; j< n-1; j++)
   for (i= 0; i< n; i++){
    ti[k++]=i+n1*j;  ti[k++]=i+n1*j+1;
    ti[k++]=i+n1*j+n1+1; ti[k++]=i+n1*j+n1; ti[k++]=-1;}

//print( ti );
  scrIFS.set_texCoordIndex = ti;

}"]
}}
#call an instance of Globe so we can see something
Globe{}

In order to call the PROTO we would use syntax that looks like: Globe { urlImg "earthtexture.gif" n 40 }.

This would wrap the texture contained in the earthtexture.gif file, around the sphere that had 40 steps around it (very fine).

Let's look at the PROTO in a little more detail.

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