I figured I would do a quick little step by step on making panel line breaks with T-Splines. The first thing is to make sure that you have an isocurve, or isocurve loop that follows the panel line break that you want. This sometimes can be tricky – in the case of this windshield, I did the topology layout with this in mind. Here’s the loop of isocurves that I want to form the break on – it’s the junction between the main body and the front windshield: Now just run tsBevel, the options I use for something like this are: Segments = 5, Positioning = Distance, Keep on Face = Yes, Retopo Snap = No. You’ll need to play around a bit with the bevel distance, in this case I found that 0.09 worked nicely, but you’ll have to adjust it for each model, depending on size. Here’s what you get: Now select the middle face loop , and set your drag mode to UVN: Now just push that face loop inwards using the normal (blue) arrow. I like to do it numerically, so that I can make them consistent. I used a value of -0.05 here, but again you’ll have to play around a bit for each application. Now just run tsMakeUniform. You should do this after every change in topology. In smooth mode you get this: It’s quick, it’s easy and it looks good. Can’t beat that!