New supported features:
- 3D/spherical brush.
- Falloff (custom falloff not yet, because that needs some more ui reorganization which is better done when we have a better understanding of what settings we need exacty).
Currently, the depth of the brush is only sampled once per stroke (when first pressing the mouse button). Sometimes it is expected that the depth of the brush can change. However, implementing that in a good way is not straight forward and might need additional options. Therefore, this will be handled separately (talked about this with @Simon Thommes (simonthommes)). I already did some experiments anyway, which I'll mention here for future reference.
Simply resampling the distance all the time, somewhat works, not super well when the brush is actually changing the "depth".
Here it is not clear whether one wants to brush up or away from the camera.