This is on MacOS, nightly build from October 22. A little old, but not ancient.
I’m seeing a strange “gradient” effect when using Mask Volume in Editor Extra Effects. Rather than a sharp cutoff from the inside to the outside of the masked volume, there’s this odd gradient from the normal values in the “kept” volume to the zero values outside. I’ve attached a screenshot - this gradient was NOT present in my original data. Any ideas what’s causing this? It’s kind of annoying because I use a threshold effect after masking and it causes an “envelope” to appear around my entire volume, caused by this gradient artifact.
Thanks in advance for any ideas! I’ll check to see if this also happens in 4.8…
By default, linear image interpolation is used in slice viewers: each displayed pixel is computed as a weighted average of voxels surrounding that 3D position. So, unless the slice is positioned exactly in the center of a voxel, you always see blending of two neighbor slices. Since masking creates huge intensity change at the boundary, the effect of this interpolation becomes more visible. So, what you see is normal and should not be a problem.
You can disable slice interpolation or position slice viewer in the center of the voxel (for example, by holding down shift button while moving the mouse in an orthogonal view).
Ugh. I had a test scene that I thought reproduced what I was seeing, and I was writing up the procedure and now I can’t reproduce it.
I do have one question - does “Mask Volume” in Segment Editor Extra Effects operate differently depending on whether or not interpolation is enabled for the master volume in question? Or is interpolation just for viewing in slice viewers?
OK, after many weeks, I finally got back to this and verified that it was indeed “problem between chair and keyboard”, as they say. I was switching between viewing several volumes and lost track of which ones had interpolation turned on.