When I drag a mask over the object the selection is not uniform. Seems to be a lot of stepping. I did a search for masking issues but didn’t come across this issue. I’ve changed the mask brush and alpha but same result. I have also subdivided thinking that might be the issue. Pretty sure it is something I just overlooked but the training I’m following, the instructor is not having this issue and I can’t see anything different he is doing.
Thanks in advance
Hi @spookie33
Masking is dependent on topology. If masking is applied to a group of polygons that aren’t cleanly separated by a shared edge, there will be “stepping” visible in the masking. This effect is less prominent at higher mesh resolutions because the polygons are much smaller. The lower poly an object is, the larger the polygons get, and the more visible this issue will be.
So, switch on polyframe mode and take a look at your topology. Either the topology wont support a perfectly clean mask of the shape you want to make in that location, or your masking method is not targeting the correct polygons.
Also, Perspective mode can sometimes distort attempts to “select through” geometry. Deactivating this mode, if active, may improve selection accuracy.
Thanks for the reply! I’ll definitely try those suggestions when I get home after work today.
Thanks Spyndel! it was the perspective on causing the issue. 
Glad to hear it!
