| IDLgrWindow, IDLgrVolume and alpha channel [message #33816] |
Fri, 24 January 2003 04:37 |
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s[1]
Messages: 21
Registered: December 2002
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Junior Member |
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Hi all,
I am rendering an IDLgrVolume into a IDLgrWindow. When I get the image
data from the Window, the image has only 3 channels. How can I get the
alpha channel of this image? The alpha channel information surely must be
somewhere, because volume rendering needs it.
I include a small test program that generates a volume, renders it into a
window and gets the buffer.
Does anybody have an idea how to get the alpha channel? Are there any
settings I forgot?
Thanks for all tips,
Sebastian
FUNCTION CREATE_SIMPLE_VOLUME
;; create a simple volume containing one big red object and two small
cubes
voldim = 128
vol = OBJ_NEW('IDLgrVolume')
;; create a volume data array of size dim^3
volData = BYTARR(voldim,voldim,voldim)
FOR i=0,(voldim-1) DO volData[*,i,0:i] = 64
volData[15:45, 15:45, 65:95] = 128 ;; small cube #1
volData[85:115, 85:115, 65:95] = 255 ;; small cube #2
;; set opacity for vol
opac = BYTARR(256)
opac[0:127] = BINDGEN(128)/8
opac[255] = 120
opac[128] = 255
;; set colors
rgb = bytarr(256, 3)
rgb[0:127,0] = 255 ; main cube is red
rgb[128, *] = [0, 255, 0] ; small green cube
rgb[255, *] = [0, 0, 255] ; small blue cube
vol->SETPROPERTY, data0=volData, RGB_TABLE0=rgb, OPACITY_TABLE0=opac, $
ZBUFFER=1, ZERO_OPACITY_SKIP=1
;; center volume at 0,0,0 and fit it into a unit cube
cc = [-0.5, 1.0/float(voldim)]
vol->SETPROPERTY, XCOORD_CONV=cc, YCOORD_CONV=cc, ZCOORD_CONV=cc
RETURN, vol
END ;; of: CREATE_SIMPLE_VOLUME
PRO CHECK_VOLUME_TRANSPARENCY
;; create a simple volume
vol = CREATE_SIMPLE_VOLUME()
;; create the view for the volume
volView = OBJ_NEW('IDLgrView', VIEWPLANE_RECT=[-1,-1,2,2], $
ZCLIP=[2.0, -2.0], COLOR=[150,150,150])
volModel = OBJ_NEW('IDLgrModel')
volModel->ADD, vol
volView->ADD, volModel
;; create the window and draw
volWin = OBJ_NEW('IDLgrWindow', RETAIN=2, DIMENSIONS=[300,300])
volWin->DRAW, volView
;; get the rendered image and check for alpha
volWin->GETPROPERTY, IMAGE_DATA=image
help, image
END
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