Volume Rendering with original image colors; removing the black fill

I have a bunch of images like this:

And I am looking to reconstruct them in a 3D model. Loading the data into Paraview, I am able to do so if I use a color map (enable Map Scalars & Ray Tracing), resulting in:

However, the color data is important. If I uncheck the Map Scalars on my original dataset, I get an error that I only have 3 channels, not 4 (RGB vs RGBA), when I append it with convert -alpha on or convert -alpha set, I don’t see anything. Finally I manged to get the original colors in by removing the black color with convert -alpha copy, which results in images like:

But, when I load them into paraview, my volume rendering looks like this (cropped volume in half to illustrate):

Even though there should be no black anymore as its removed from the image data, its showing up in the volume.

My Questions:

  1. (How) can I disable the black filling? Is there somethings as threshhold I can use here?
  2. If not with Paraview, how could this be done with VTK?

My endgoal is to load into blender with BVTK

Welcome to the ParaView community!

I assume you are volume rendering your last image (as you state). The. This is unexpected behavior. Here is an (old) tutorial I wrote up on controlling the opacity for volume rendering: https://www.paraview.org/Wiki/Volume_rendering_-_Fire. If that doesn’t work, try using Clip/ by Scalar, and remove all of your cells that are black. Then post another picture.

Thanks for the help Walter!
By playing with the color map points there does seem to change a bit, but either only the colors themselves, or the whole things disappears all together around one threshold.

The Clip with Scalar I applied, but I am not sure if it works as Paraview crashes before it shows anything :frowning:

Can you give us a file that we can try? Oh, and good directions what you are trying to do?

Here you can find the dataset. The AlphaMask is the one I used.


  • Import
  • Show dataset
  • Unselect Map Scalars
  • Show Volume Projection