[EMAIL PROTECTED] (2007-07-22 at 1801.32 -0400):
> Thank you very much for your examples, they also helped me understand a bit
> more the "Save as GIH" dialogue. One of the things that strikes me as
> illogical was that you start the ranks from the bottom and go to the top as
> you add more ranks?... It seemed more logical to me to have the first
> governing rank on top, while the second is underneath it, etc. If you don't
> mind explaining the logic, it would be great and might teach me a thing or
> two about GIMP and this concept.

Origin of coords does not need "common sense", just that the rules are
known and not ignored. Someone decides 0,0 is somewhere, and +X goes
this way and +Y this other. That applies both to maths and to this. :]
Sadly "known" is not 100% in GIH-land (I remember Gimp 1.2 dialog had
controls to the side and even allowed 5 dimensions, even if only 4
controls were provided... what was the 5th?), at best you have to go
with empiric conclusions.

> So, taking your brush "pipe-brush-pressure-angle-and-tilts.gih", I read the
> first rank for x-tilt, composed of 3 cells. Next rank, y-tilt, created from
> 3 cells as well - so far, that's a 9 cell matrix with the numbers 1 through
> 9, printed according to the X/Y tilt. Then you have an angular brush with
> two ranks (the black and red colored numbers governing the angle of your
> stroke, somehow the black only appears from degree 0 (upwards) to 90
> (right), from 90 to 359 the red takes over? Shouldn't it be black from
> degrees 0 to 179 and red from 180 to 359?) and the last rank, pressure,
> uses
> black and red colors for a light pressure and green and blue for harder
> pressure, alternating colors as per the angle of your brush.

I learnt that looking inside the GIH files was a sure way to get a
headache. I always looked at XCF versions, and considered GIH a nasty
manual step required to get brushes working, instead of having the XCF
as single file that had to be created and tweaked. Or even better,
having that and run-time controls to change the mappings (what goes
with pressure, etc), so not saving at all except to change "images" or
default mappings.

The 3D angle-and-tilts brush works, giving ~90 deg to each of the four
layers. But yes, I checked the 4D pressure-angle-and-tilts brush with
mouse, and it strangely gives a 90-270 instead of 180-180. I thought
(or so my memory says I did), that it would select one of two groups
by angle (KR or GB), and then select the exact layer by pressure (if
it got to KR, K or R). I am unable to test pressure (or tilt), but if
you say it selects two colours for high and the other two for low,
that part seems to match what I thought.

When the dialog was to the side, I read it this way, for 4D:

Select      Select        Select      Select
group of -> one layer  -> cells in -> cell in
layers      from group    Y axis      X axis

The example brush has the following:

Pressure -> Angle      -> Y tilt   -> X tilt

So the path would be, with mouse (fixed pressure, fixed 0 tilt):

KR GB    -> K R        -> 2 5 8    -> 5      -> Black or red 5s
Mouse       0-90          0-deg       0-deg
pressure    or            tilt        tilt
says        90-360
"1st"       (?)

Maybe there is a bug, or I set something wrong in the save dialog or
some hidden rule escaped my experiments (maybe there is "no layers in
groups" after all, go figure).

> P.S. I'm "explaining" these things back to you just to make sure I
> understood things right, please don't feel offended if I state the 
> "obvious"
> :) But your example is much appreciated, it proved the options work as
> expected (except that weird angular decision) and also gave me an insight
> the manual was not able to provide.

No problem, I remember the issue is far from documented, it seems
barely anybody knows how things work or worse, how it should work, so
the topic quickly gets discarded. Experimenting without going into the
deeper levels is enough for me, even if not being 100% sure the things
are correct. This is the third time, at least, years ago first, the
IRC session second, and some parts still unclear. Sadly all the manual
steps (including for single image brushes) makes the brush system
really tedious and clunky, so I understand that as things get more
complex they get less use and less understanding.

Good luck trying to figure any misconceptions or missing details. See
the issue with 90+270 deg instead of 180+180, and I would add why you
can control the cells up to 1000 or why playing with different buttons
makes other values change (cell size -> number of cells and count in
first rank, but not other ranks). Best would be figuring how it was
planned to be.

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