; xModels Tutorial 2:  Animation

; Moving images are more interesting than still images.
; An animated image is displayed on the computer screen
; by showing a sequence of "frames" in rapid succession,
; with small changes from one frame to the next.  In
; xModels, a number range such as 1:5 is used to specify
; a value that changes from frame to frame in the animation.
; For 1:5, the value is 1 in the first frame and is 5 in
; the last frame.  Between the first and last frame, the
; value changes by the same amount in each frame.  This
; file defines an animation for xModels.


animate 60  ; An animated scene MUST begin with the
            ; word animate, followed by a specification of
            ; the number of frames in the animation.  Here,
            ; there will be 61 frames, numbered from 0 to 60.

background yellow ; The "background" command is used to
            ; specify a background color for the scene.
            ; (Used here just for fun.)

square scale 1:5 rotate 0:90 ; Specifies a different
            ; square in each scene.  The first square has
            ; size 1 and is not rotated at all.  The
            ; second square is a little bigger and is
            ; rotated a bit (by 1.5 degrees, to be exact).
            ; The last square will be 5 units large and
            ; rotated through an angle of 90 degrees.

circle scale 1:5 5:1 translate 6 6 ; This starts out
       ; as a 5-by-1 ellipse and ends up as a 1-by-5
       ; ellipse.  The translate command moves it
       ; to the upper right corner of the display area.

blue

cube scale 2 translate -6:6 -7  ; The cube moves
      ; along the bottom of the screen, from the
      ; point (-6,7) to (6,7). 

line scale 4      ; A four-units long line
   rotate 0:180   ; rotate from 0 to 180 degrees.
   translate 0 7  ; The rotating line is moved 7 units
                  ; upwards.  (Note: this line is blue.)

red

line scale 4       ; A four-units long line
   translate 0 7   ; is moved seven units upwards
   rotate 0:180    ; and from there rotates through
                   ; 180 degrees about the origin.  (Note
                   ; that the order in which the
                   ; transformations are applied makes a
                   ; big difference.  (This line is red.)

; (When you render this animation, note how the image of
;  the cube changes as it moves.)