> You are going to have to spell this out for me. I
> cannot imagine why you think the OPACITY_TABLE0
> limits you to 100 values of gray scale. Sorry for
> being on the dense side of the opacity scale. :-(
>
> Cheers,
>
> David
Ok, so I think that a practical example could help: the following
program makes a spherical volume made of concentric shells, following
a sin(radius) law.
I use a linear grayscale as RGB_TABLE so that the maximum value is
white and the minimum is black.
Then I also use a linear Opacity from 0 to 15, because I want to well
view throug all the shells until the center.
As you see, the final image is a byte array and its maximum value is
142.
In my application the maximum gray is in the range 10 to 20, but I
want an image with 256 gray levels not only 10 or 20 grays.
Thanks for your help
Gianluca
Here is the sample program:
x_pix = 100.
y_pix = x_pix
z_pix = x_pix
Volume_Color = (findgen(256)/255) # [255,255,255]
Volume_Opacity = (findgen(256)/255) * 15
;Make a spherical volume with density in shells:
Volume_Data = fltarr(x_pix,y_pix,z_pix)
FOR x = 0., x_pix-1 DO BEGIN
FOR y = 0., y_pix-1 DO BEGIN
FOR z = 0., z_pix-1 DO BEGIN
Volume_Data[x,y,z] = SQRT((x_pix/2.-x)^2 + (y_pix/2.-y)^2 + (z_pix/
2.-z)^2) ;distance from center
ENDFOR
ENDFOR
ENDFOR
Volume_Data = Volume_Data * (Volume_Data LE (x_pix/2.)) ;cut at x_pix/
2 radius
Volume_Data = SIN(Volume_Data) ;make sinusoidal shells
;convert to byte as required by IDLgrVolume
Volume_Data_byte = BYTE((Volume_Data / max(Volume_Data)) * 255.)
;3d graphic objects
oWindow = OBJ_NEW('IDLgrWindow', RETAIN=2, DIMENSIONS=[400,400])
oView = OBJ_NEW('IDLgrView', COLOR=[0,0,0])
oModel = OBJ_NEW('IDLgrModel')
;Create Volume Object
oVolume = OBJ_NEW('IDlgrVolume', Volume_Data_byte, LIGHTING_MODEL=0,
INTERPOLATE=1, $
OPACITY_TABLE0=Volume_Opacity, COMPOSITE_FUNCTION=0,
ZERO_OPACITY_SKIP=1, ZBUFFER=1)
oModel -> Add, oVolume
;set display window
Display_XRANGE = [0, x_pix-1]
Display_YRANGE = [0, y_pix-1]
Display_ZRANGE = [0, z_pix-1]
Display_xSize = x_pix
Display_ySize = y_pix
Display_zSize = z_pix
Display_Diagonal = SQRT(Display_xSize^2 + Display_ySize^2 +
Display_zSize^2)
Display_xCenter = x_pix/2
Display_yCenter = y_pix/2
Display_zCenter = z_pix/2
oModel -> TRANSLATE, -Display_xCenter, -Display_yCenter, -
Display_zCenter
oModel -> ROTATE, [1,0,0], -90
oModel -> ROTATE, [0,1,0], -60
oModel -> ROTATE, [1,0,0], 30
oView -> SetProperty, VIEWPLANE_RECT=Display_Diagonal*[-.5,-.5,1,1],
ZCLIP=Display_Diagonal*[.5,-.5], EYE=Display_Diagonal
oView -> Add, oModel
;Display Object Hierarchy
oWindow -> Draw, oView
;Catch the Window
oWindow -> GetProperty, IMAGE_DATA=IMAGE
help, IMAGE
print, max(IMAGE)
stop
OBJ_DESTROY, oView
OBJ_DESTROY, oWindow
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