A GSoC proposal to work on a canvas with realistic color mixing

[Boudewijn Rempt]

On Monday 22 March 2010, JL VT wrote: 

> The alternative proposal I've been thinking for GSoC would be more
> paintops. I'm aware that Lukas is working on those, but there's plenty of
> textures in the world and ideas floating around, enough for some
> parallel work.
 
Some interesting things could be built on top of the sumi-e/hairy brush. For 
instance, impasto effects (though that would likely need some canvas and 
display support, both opengl and qpainter), more smeary/block effects.

> Hatching and halftones are one of those very interesting textures that
> could never go wrong in a paint-from-scratch application. It's
> actually not painting in itself, but you said you were interested in
> features for comic artists!.
> 
> One way to implement hatching and halftones would be to reimplement
> gimp-painter's mixbrush into Krita (which does much more than just
> mix). This time I actually compiled the gimp with the patch and toyed
> with the tool for half an hour. It's an excellent tool, with enough
> options to achieve a great variety of textures and colormixing at the
> same time, achieving something that looks convincingly more
> traditional than any other tool in the GIMP.
> 
> The drawbacks of the mixbrush for hatching and halftones is that I'm
> limited by the texture I'm using, being unable to add other special
> effects beyond the linearity of what you can observe in this video
> (around minute 2:40)
> http://www.youtube.com/watch?v=dNvcifmXGmw
> Which is halftoning based on a texture (you can briefly see its
> thumbnail during the demonstration). [I can't get enough of the music

Yes, that looks like an interesting effect. It wouldn't be much more than a 
week or so to implement in Krita, though, and it probably shouldn't a paintop 
on its own, but a color source or something like that for the pixel brush.

> So, for example, I couldn't decide the ANGLE of the hatching, or
> making non-linear effects like adding more hatching patterns on top of
> the basic one with increasing tablet pressure, like this:
> http://pentalis.org/hatching_example.png

There are a number of studies out there on hatching -- I don't have the urls 
handy, but it used to be a quite fashionable subject in academia. One thing 
that is even more interesting than a plain hatching brush engine, would a way 
to fill a selection with hatching with direction and weight, i.e., you want to 
fill the wing of a bird or the hair of a person with hatching/strokes -- 
select the area, then paint in the selection, and the algorithm will do the 
right thing. 

> On the other hand, the advantage of implementing something like the
> gimp-painter-mixbrush would be its versatility, although I think it
> has too many options and can easily confuse, therefore it'd be better
> to implement it in the form of separate paintops which as a set are
> equivalent to all of gimp-painter-mixbrush's functionality.

I'm not sure about a plain port of gimp functionality: in general, for 
inspiration either look in academic papers, or look at Corel Painter. I'm fine 
with a proposal to enhance the existing brush engines/create new ones, but we 
need to dig a little deeper still. I'll ping you on irc.

> Yes sir!, I even had my own system.
> http://www.scribd.com/doc/217723/Gidra-V-01

Here's mine: http://www.valdyas.org/aurea.html -- we never sold it, but we've 
been running a campaign for about 14 years using the system.



-- 
Boudewijn Rempt | http://www.valdyas.org