[GSoC proposal] Airbrush and Calligraphy paintops

[Fela Winkelmolen]

Hi all,
Thanks for the feedback =)

On Thursday 27 March 2008, Boudewijn Rempt wrote:
> On Thu, 27 Mar 2008, Fela Winkelmolen wrote:
> > I'm posting here a draft of my Google Summer of Code proposal, in case
> > anybody has comments or suggestions
>
> I think you need to add a bit more about yourself, you current skill level

Yes, I was planning to do that in the definitive proposal =)

> etc. I also think you should try to be more specific about the goals, i.e,
> define more closely what the airbrush and calligraphy effect would become.

Well the effect of the airbrush should be to simulate a real world airbrush 
(if that is what you mean).
I'm not really sure yet what I want with the calligraphy tool. The basic idea 
was a Inkscape like calligraphy tool, but that hasn't terribly much to do 
with real media.

The idea of Matthew of a 3d contour seems interesting. Allowing it to have 
only one contour, it should be quite simple to implement, even if that means 
the simulation isn't very accurate. But I'm very open to other ideas

> [...]
> > Also the calligraphy tool may need to be a bit more sofisticated. The way
> > it's described above it behaves mostly like the Inkscape calligraphy
> > tool.
>
> maybe add a "splicing" option -- if you use a real goose-feather nib, if
> you press too hard, you get two lines instead of one. Also, check out the
> digital ink feature of Corel Painter -- maybe we can use something similar
> here.

I think my roommate has Corel Painter installed, so I will have a look when he 
comes home. Does anybody knows if it works under wine?

>
> Boudewijn



On Thursday 27 March 2008, Matthew Woehlke wrote:
> > There are airbrushes that separate the function for air and paint flow
> > (dual action airbrushes), but I'm not sure that makes sense in the
> > digital version.
>
> What is the effect of these?

I'm not really sure, that's why I asked. I've never used a real airbrush 
myself. According to wikipedia[1] a dual action airbrush "allows for greater 
control and a wider variety of artistic effects".
It might be that you can control the level of atomization controlling the 
airflow, in that case it should be possible to simulate a dual action 
airbrush with the granularity parameters.

> [...]
> I would probably approach this as three parameters; flow rate, particle
> size, and particle density (actual opacity of particles, which does in
> fact need to be a fourth parameter, should come from the pigment, not
> the tool). Rate is mostly a measure of how many particles are deposited
> per unit of time (as you say, with maximum density, this equates to rate
> as we understand it now), and makes sense to be controlled real-time.

As I understand it, flow rate is simply what I called rate. The implementation 
will be a bit different if the granularity is infinite (particle size = 0) 
but the general visual effect should be the same, and from the user's point 
of view it should be the same.

Density seems to me to be the same as the rate, or better, if the rate is 
higher that means you will get a higher density in the same unit of time.

> > Another parameter might be how "blurred" the stamp is around the border,
> > or, in the case of particles, how concentrated the particles are at the
> > center compared to the border.
>
> I don't understand what you mean by "blurred", but if it's just the
> relative particle density, that makes sense.

An airbrush stroke has a lower particle density near the borders, the amount 
of that difference is what I mean to make configurable.

I'll write a new proposal based on these comments tomorrow.
Good night!
- Fela

[1] http://en.wikipedia.org/wiki/Airbrush#Trigger