Every time I visited the Mrtrix3 website, I cannot stop to enjoy those alluring images displayed on the home page, in particular for the 3D images of whole-brain tractography:
Probably the main thing you’re missing at the moment is track lighting. It’s off by default because it hurts performance, but as long as your number of streamlines is not absurd it runs quite well. Check near the bottom of the mrview Tractography tool.
Apart from lighting/shading, the trick to the top one is combining with an anatomical (or other) volume and playing with the opacity/transparency of that volume. That gives an extra sense of depth, because the “fog” of that volume gets denser the deeper you go into the view. Additionally, for that top one, note that I also used clip planes. You can’t easily see them, because the volume itself is so transparent, but it does make a significant difference in showing the front of that tractogram in bright colours, and only going “into the fog” closer to the back/side edge of the image.
Note that, apart from fancy-ness, a good sense of depth is also a very useful cue for visualisation and navigation. It’s more than just pretty pictures; making them pretty in specific ways can also be desirable for specific applications!
