; xModels Tutorial 1:  Basic Ideas

; A program written in the xModels scene description
; language is basically a list of the objects in the
; scene, with "transformations" that say how the objects
; are sized, oriented, and placed.  There are a few
; other things that can occur in programs.  This
; program contains examples of the basic objects
; and some of the transformations that can be used
; in a program.  It also shows how to use color.

; A semicolon, like the one at the left is the beginning
; of a "comment" which is ignored by the computer.  A
; comment ends at the end of the line.


square  ; A square is one type of basic object.
        ; Putting its name in the scene description
        ; adds a square to the image.  A basic square
        ; is a rather small square at the center of
        ; the image.
        
square scale 3 ; This is ANOTHER square in the same
        ; image.  The transformation "scale 3" placed
        ; after an object causes that object to be
        ; magnified by a factor of 3.  Every point in
        ; the object is moved away from the origin to
        ; three times its original distance.  Since
        ; the basic square was centered at the origin, 
        ; a scaled square is also centered at the
        ; origin.
        
red ; The command "red" tells the computer to draw the
    ; following objects, up to the next color change
    ; in red.  Other color commands include green,
    ; blue, cyan, magenta, yellow, black, white, and gray.
    ; (It is also possible to specify "RGB" colors
    ; and "HSB" colors.  See the full documentation for
    ; details.)
    
circle translate 6 6 ; A "circle" is a small circle
    ; at the center of the screen, but the "translate"
    ; transformation is used here to move it over 6
    ; units and up 6 units from its original position.
    ; This will show in the image as a small, red
    ; circle centered at the point (6,6).
    
circle scale 5 translate -6 6  ; Transformations can
    ; be combined.  The circle is FIRST scaled by
    ; a factor of 5, and then the resulting object
    ; is moved 6 units to the left and 6 units up.
    ; The result is a circle of diameter 5 centered
    ; at the point (-6,6).  The drawing color is 
    ; still red for this circle,
    
blue  ; Color changes to blue for following objects

square scale 5    ; Start with a square,
   rotate 30      ; rotate it 30 degrees about the origin,
   translate 6 -6 ; then move it 6 units over and 6 down.
      ; (Note that you don't have to list all the
      ;  transformations on one line.)
      
square scale 6 2  ; A scale command can also have two or  
  translate -5 -5 ; three parameters.  "scale 2 6" magnifies
                  ; by a factor of 6 horizontally and
                  ; 2 vertically.  Scaling a square in
                  ; this way gives a rectangle.

green

cube scale 4 translate 5 0  ; A 1-by-1-by-1 cube is
    ; magnified by a factor of 4 and translated
    ; 5 units to the right,
    
cone scale 4 translate -5 0 ; The cone shows up
    ; 5 units to the left of its default position
    ; at the origin.

magenta ; A bright purple-ish color

cylinder scale 4 translate 0 5 ; The cylinder
    ; shows up 5 units above the origin
    
line  scale 6 translate 0 -7 ; Finally, a humble line.
    ; The basic line is one unit long, extending along
    ; the x-axis from (-0.5,0) to (0.5,0).
    ; Here, it is scaled to a length of 6 and moved
    ; down 7 units.

; You can render this scene by clicking on the "RENDER"
; button.  You should be able to find all the objects
; listed above in the picture.  The colors will help
; you identify them.  The 3-dimensional objects will
; look sort-of distorted because they are being projected
; onto the screen from the point (0,0,20).  The near side
; of the cube, for example, looks bigger than the far
; side (as it should, really).