I’m glad the OP asked this question, as I’m getting a bit hung up on my masks as well. In comparison to Kent’s, my mask stroke looks somewhat less defined, even though I’m using the same brush size and strength. It makes sense that the mask stroke fidelity would depend on the mesh density, but I’m following along closely, so it’s not clear why my mesh density would differ from Kent’s. I’m not gonna sweat it too much for now but it is a tad worrisome, in that my fins aren’t quite as “robust” when I pull out the masked area with the snake hook. As a result, I can only smooth so much without completely collapsing the fin shape. I will note that, at about 13:50 in the video, Kent mentions that it’s harder to get smaller details at the current voxel size (but he doesn’t want to remesh the whole thing at this point). So, I’m going to go with that and hang on until we get to incorporating dynamic topology.