Re: [Gimp-developer] Problems with brushes

[Martin Renold <martinxyz gmx ch>]

hi Richard

On Sun, May 20, 2012 at 10:16:01AM -0700, Richard Gitschlag wrote:
> 
> "Incremental" means that every application of paint in a stroke layers on
> top of the previous one.  I recommend never using it outside special cases
> - most brushes have a spacing of 10-15% or so which means that any given
> pixel along the stroke area will end up 'painted' up to 5-7 times over. 
> Normally this is a moot point but with incremental option this means that
> the opacity will end up being applied 5-7 times over too -- you lose the
> ability to get a stroke with a predictable OVERALL opacity value (even an
> opacity setting of 10%, if incremental, yields an end result up to 40-50%
> opacity).  This is as technically correct as it is utterly undesirable,
> but it's a limitation in how GIMP handles painting actions internally so
> it's virtually impossible to fix.

Incremental mode is very useful, especially when painting with a tablet.

It has the advantage that the effect of the brush doesn't depend on whether
you have painted over that area already in the same stroke.  This makes the
stroke more predictable.  The sudden change of behaviour of your painting
tool at the end of a stroke can be very unnatural.  Especially when you try
to build up a shade with repeated faint strokes over the same region.

The opacity problem (stroke opacity vs dab opacity) can be fixed
mathematically.  Grep for OPAQUE_LINEARIZE in the mypaint source code.

-- 
Martin Renold