Meet the Metaphors

World in the Hand

In last exercise, you have been, asked to move the viewpoint around the centre of your Local node, looking always towards the centre of the basis, and more precisely towards a house placed in that centre.

This way to move around the Viewpoint is usually known as the "world in the hand" Metaphor.


A Metaphor is a way to explain to users of a program how    to use its interface. You say "do it as if you where doing something else that you already know". The most well-known one is of course the "Desktop" 2D Metaphor invented by Xerox, developed and popularised by Commodore and copied by Microsoft and Apple. It says that to access the information available in a computer, you should have the same behaviour as in front of a real desktop. You could open a "folder"  from which you get a "file" that you could "open", "write" into and "close"...

As 3D world is more difficult to work with than 2D one, and there are lots of metaphors around to represent the way to deal with that world.

The Flying metaphor

Flying Plane

   Can roll, pitch and yaw the view and can move forwards (along the -ve z' axis).

Plane Movement ScreenShot

Flying Saucer

   Can move up, down, left, right, forward and backwards relative to local heading (ie along the x', y' and z' axes).

Saucer Movement ScreenShot

Flying Superman

Exercise 8 : Implement Flying Plane or Flying Saucer Metaphor


Useful vectors such as x', y' and z' are stored in the Transform3D object.
The first 3 rows of the first column represent the x' axis
The first 3 rows of the second column represent the y' axis
The first 3 rows of the third column represent the z' axis

Transform3D explanation

the negative z' axis is the direction in which the view is facing.

Other Metaphors

On the Ground metaphor

The Walking metaphor
The driving metaphor

The be yourself and move around metaphor

... the virtual reality metaphor

What about interaction (required for the implementation of certain metaphors)?

Mouse Picking

A ray between the mouse and your eye

The magic wand

This is just selection... what about manipulation of objects in the scene...


the object in a cylinder

the object in a sphere