[Paraview] isosurface transparency issues

[W. Bryan Smith]

apologies if this posted twice... but i did not 
see it.

Hi,

I am running ParaView 2.4.3 or 2.5, compiled 
with or without mpi support, and I am seeing 
something unexpected:

I am loading two separate 3-D images saved as 
legacy vtk files and attempting to render 
isosurfaces of the data.  the images are 
thresholded, such that all the pixels in image1 
are equal to 10, and all the pixels in image2 
are equal to 20 (just for example).  each image 
defines an object that is distinct in space from 
objects in the other image.  so far, this is 
working fine: i read in both images, render an 
isosurface at value 10 for image 1, at 20 for 
image 2, and i can color them separately without 
any trouble.  problem is, when i set some 
transparency values to the isosurfaces and then 
rotate the volume to get a different angle, one 
of the isosurfaces occludes the other such that 
it is entirely invisible.  in case that is not 
clear, here are a couple images of what i am 
talking about:

http://ncmir.ucsd.edu/~bryan/PVimage001.jpg
http://ncmir.ucsd.edu/~bryan/PVimage002.jpg
http://ncmir.ucsd.edu/~bryan/PVimage003.jpg

so the gray blob in the top left corner of 
PVimage001.jpg appears to have jumped to the 
foreground in PVimage002.jpg, even though the 
green one, in reality, should be in front.

can someone please tell me what i am doing wrong 
(and/or if you need more info to help 
troubleshoot this)?

thanks,
bryan


W. Bryan Smith
UCSD/NCMIR
9500 Gilman Drive # 0608
La Jolla, CA, 92093-0608

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The illusion that we are separate from one another
is an optical delusion of our consciousness.
                                -Albert Einstein
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^