GLSL transparency along line of sight

Hi !
I notice that whenever I have multiple objects along the line of sight, the realtime transparency is not calculated correctly. Specifically, objects that are highly transparent (alpha close to zero) can appear dark against a background of more opaque objects. In the example below, it should be possible to see through the dark cubes to the more opaque cubes behind them. Is it possible to have the transparency calculated more correctly ?

Longer explanation for those who are interested : I work at the Arecibo Observatory, and I’m attempting to import HI data from FITS files into Blender, so I can look at my data in realtime in 3D. Hence the thousands of cubes, which are imported via a Python script (so any fix needs to be easy to apply or at least scriptable). They render correctly, but that bit’s easy - it’s the realtime I’m interested in. If there’s another open source program that can handle this stuff I might be willing to explore it.

Thanks !


have all your cubes the same material setting?
Maybe you should post an example (blend-file) with a few cubes …

Oh that’s weird, my reply didn’t show up… I hope I didn’t post it somewhere else by mistake…

I found another approach that does exactly what I’m after. Instead of using GLSL I can enable “Transp” in the Draw Extra part of the Draw panel in the object settings. I’ll bet that button’s been there for years and I just never noticed it. :stuck_out_tongue:

Of course, it might be nice to solve this for GLSL materials since they give so many more options. Fortunately for my purposes I don’t need (or want) to apply to textures or anything clever like that. Still, here is a test file. You should see the apparent transparency change depending on which cube is selectedTestingCubes.blend (122 KB).

If the foreground cube or any other object is selected, then the background cubes are (correctly) clearly visible. If the background cubes are selected then they become obscured by the foreground cube, which is not correct since the foreground cube has less transparency. This is the effect I’m seeing in my main file. I’ll post images when I get time, if this is unclear.

now i understand,
that is the setting for the “highlight” of the selected objects.
And the way this is done can be configured -
even like one cannot see a difference between a selected object
and all other objects.
Next there are options for every single object how it should be
represented (drawn in the 3D-View).
And last, in the user-preferences there are settings for the colouring
used in the 3D-View…

I know selected objects are outlined and highlighted, but I wasn’t aware that this should change their transparency. How can I turn this off ? Also, in my main file there are many hundreds or thousands of different meshes, so it is not practical to select or unselect all of the meshes with incorrect transparency.