VRML, 3D, and Transforming

This is virtual reality we're talking about after all, and it's 3D.  When you have three dimensions, you get to work with three directions--height, width, and depth.  They're simply directions you've taken for granted in the everyday world, but now they have a use in a computer language.

Height is a measure of how tall something is, width is a measure of how wide something is, and depth is a measure of something's length, that is, how far it comes out at you from your screen.  VRML is centered around this 3D world, so be prepared to use these three standard measurements in defining lots of things, ranging from the height of a cylinder to the width of a bounding box.

The Transform Node

Transform {
   children           []
   translation	      0.0 0.0 0.0
   rotation	      0.0 0.0 1.0 0.0
   scale	      1.0 1.0 1.0
   scaleOrientation   0.0 0.0 1.0 0.0
   bboxCenter	      0.0 0.0 0.0
   bboxSize	     -1.0 -1.0 -1.0
   center	      0.0 0.0 0.0
   addChildren
   removeChildren
}

• The children field is a list of nodes.  You'll usually see this filled with Shape nodes that build complex shapes.  If you want to have two or more nodes in this field, separate their nodes with commas.
• Use the translation field to tell the browser where the entire system should go.  Here is the first application of that three dimensional system from before.  The first number defines a value along the X, or horizontal, axis, the second number defines a value along the Y, or vertical, axis, and the third number defines a value along the Z, or depth-based, axis.
• The rotation, scale, and scaleOrientation fields deal with manipulating the Transform node's children themselves.  As you could probably figure out, you would use these the first to rotate by a number of degrees, and the last two to scale (or resize) the children.
• bboxCenter, bboxSize, and center are used to tell the browser the size of the bounding box, which will be covered in a later tutorial.
• addChildren and removeChildren, believe it or not, are actually commands that take nodes and do the respective action.  For example, if you were to send a node to the addChildren field, that node would be added as a child of the Transform node.

Whenever you put this node into use in your code, a new coordinate system is created.  Coordinate system is just the coder's way of saying that a miniature world is created inside of the larger world.  This miniature world contains nodes...that's right, the ones that were put into the children field.

If you use the translation field, you're moving this coordinate system to another location, as defined when you put in those coordinates.  By default, the Transform node's contents are dumped right into the center of the parent world.

Enough documentation...let's go see what this thing can do.

Movin' Stuff

#VRML V2.0 utf8

Transform {
   children [	# A simple cone
      Shape {
         appearance Appearance {
            material Material {
               diffuseColor 1.0 0.0 0.0	  # Red
            }
         }
         geometry Cone {
            bottomRadius 2.0
      }
      }
   ]

   # Translate it two units upwards by changing the Y value:
   translation  0.0 2.0 0.0
}

# Now let's put something under it
Shape {
   appearance Appearance {
      material Material {}
   }
   geometry Sphere {
      radius 2.0
   }
}

#VRML V2.0 utf8

Transform {
   children [	# That same simple cone
      Shape {
         appearance Appearance {
            material Material {
               diffuseColor 1.0 0.0 0.0	  # Red
            }
         }
         geometry Cone {
            bottomRadius 2.0
	 }
      }
   ]

   # Let's go right two units, up three, and backwards one:
   translation  2.0 3.0 -1.0
}

# Now let's put something under it
Shape {
   appearance Appearance {
      material Material {}
   }
   geometry Sphere {
      radius 2.0
   }
}