ArtRage uses a rendered stroke-based algorithm, rather than a dab-based algorithm that most other digital programs use. The stroke-based algorithm leaves artifacts where you force the brush-head through a corner of radius smaller enough that the inner edge of the stroke overruns itself. To prevent tools which have semi-transparent paint from showing a multi-type effect in sharp corners ArtRage clips out the intersections.
The result is that if you put certain tools through sharp reversals there will be 'notches' on the inside of the curve where the overrunning edge has been clipped out. (The maths of a brush head passing through a tight corner is phenomenal).
The artifact is only visible at certain corner radii with the tool.
The airbrush tool and the pencil in 'precise' mode dont have this issue - they use a more traditional dab-based approach to their rendering.
We're looking at ways to improve the tight corner issue in future releases of ArtRage.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"