Stroke width display improvement
GPencil strokes are now drawn with z-depth controlled line width, which is useful in most of the cases. However In some cases we would like to have more controls over that. For example, some graph drawings may require constant line width no matter how far it is from the camera, in some cases clamping the thickness or scaling the z-influence would also be useful.
- z-influence adjustments (as well as a switch to enable/disable this).
- thickness clamping.
- z-thickness curve (probably doesn't need to be this way).
- absolute/relative thickness related to viewport size (like Freestyle used to do).