XVOLUME_ROTATE

The XVOLUME_ROTATE procedure is used to programmatically rotate the volume currently displayed in XVOLUME. XVOLUME must be called prior to calling XVOLUME_ROTATE. This procedure can be used to create animations of volumes and isosurfaces.

This routine is written in the IDL language. Its source code can be found in the file xvolume_rotate.pro in the lib/utilities subdirectory of the IDL distribution.

Examples

The following example creates an animation of the volume currently displayed in XVOLUME. It does this by rotating the volume through 360 degrees in increments of 10 degrees using XVOLUME_ROTATE, and writing the volume to a BMP file for each increment using XVOLUME_WRITE_IMAGE. It then loops through the images and uses TV to display each image.

First, display a volume as follows:

; Create a volume:
vol = BYTSCL(RANDOMU((SEED=0),5,5,5))
vol = CONGRID(vol, 30,30,30)
; Display volume:
XVOLUME, vol

Now, use the XVOLUME interface to modify the orientation and appearance of the volume or isosurface as desired. Once you have the volume or isosurface displayed the way you want it, run the following program. To try the example, save the following code in a file named spin_volume.pro, then compile and execute the procedure. (If you are viewing this topic in the IDL Workbench help, you can click on the code block below to compile the routine, then enter spin_volume at the IDL command line.)

PRO spin_volume
   inc = 10. ; degrees.
   ; Create images
   FOR i=0,(360./inc)-2 DO BEGIN
      XVOLUME_WRITE_IMAGE, $
         'spin' + STRCOMPRESS(i, /REMOVE_ALL) + '.bmp', 'bmp'
      XVOLUME_ROTATE, [0,0,1], inc, /PREMULTIPLY
   ENDFOR
   XVOLUME_ROTATE, [0,0,1], inc, /PREMULTIPLY
   ; Read images
   img = READ_BMP('spin0.bmp')
   siz = SIZE(img, /DIM)
   arr = BYTARR(3, siz[1], siz[2], 360./inc-1)
   FOR i=0,360./inc-2 DO BEGIN
      img = READ_BMP( $
         'spin' + STRCOMPRESS(i, /REMOVE_ALL) + '.bmp', /RGB)
      arr[0,0,0, i] = img
      PRINT, i
   ENDFOR
   ; Display animation
   FOR i=0,2 DO BEGIN ; num rotations
      FOR j=0,(360./inc)-2 DO BEGIN
         TV, arr[*,*,*,j], /TRUE
      ENDFOR
   ENDFOR
   TV, arr[*,*,*,0], /TRUE
END

Syntax

XVOLUME_ROTATE, Axis, Angle [, /PREMULTIPLY]

Arguments

Axis

A 3-element vector of the form [x, y, z] describing the axis about which the model is to be rotated.

Angle

The amount of rotation, measured in degrees.

Keywords

PREMULTIPLY

Set this keyword to cause the rotation matrix specified by Axis and Angle to be pre-multiplied to the model’s transformation matrix. By default, the rotation matrix is post-multiplied.

Version History

5.4	Introduced