Gimp Gih Matrix in Short - Part I
Autor: Americo Gobbo | Publicado: 2014-02-10T19:24:00-02:00



Samples of my gih sample matrix with 2 dimensions and the first brush
series based in this tutorial. The brushes are thought as bristle kind.


Introduction
The more important thing to build dynamic brushes with more than one dimension, is to imagine how it must works and the kind stains variations. To make dynamic brushes with many dimensions without this study, for me, don't make sense... because two things in special: is very difficulty to control and organize the brushes by kind, the effect is very randomly and is better simplify… all an unique dimension with random behavior.

Dynamic raster gimp brush - the gih matrix in short

Explaining in short an way to understand how to build a n dimensions gih matrix and the final layers on gimp. For that I’ll write few examples of matrix, with two and three dimensions.

First case - 2 dimensions gih matrix
To understand better is interesting imagine the aspects as a possible change state... normally the aspects of 1st dimension modify the aspect of 2nd dimension, in this sense the 1st dimension aspects are a kind modifier of the 2nd dimension aspects.

I've imagined a matrix with 2 dimensions, the first dimension with 2 aspects (random) and 2nd dimension with 4 aspects (angular). To calculate the number of necessary layers on gimp we must multiplied the ranks of two dimensions =&gt; 1st(2) x 2nd(4) = 8 layers.

But is useful to explain a bit more how we can transform the aspects in the correct order on layers. When we talk about aspects… we are talking about the number of variations of the these aspects could have in stroke brush sequence. In many cases is useful to draw a sketch on paper to imagine how it works and mainly how it will be build.


Box gih matrix array metaphor.

The 1st dimension is formed by 2 aspects random (without and with up-down lines), each of them is a variation of 2nd second dimension aspects, in my case, without and with two lines that are up and down of stains of 2nd dimension.


Aspects of my gih matrix sample.

The 2nd dimension is formed for 4 aspects (Angular = 0, 90, 180 and 270 degrees), each one is different stain, in my case, I've make 4 images (one for each aspect):

- - - | Hyphen dash line =&gt; 0°
. . . | Point dash line) =&gt; 90°
/ / / | (slash kind line) =&gt; 180°
\ \ \ | Backslash kind line =&gt; 270° - -90°
To make the combination of these aspects and to combine a precise layer order in gimp is normally the difficulty, so make a sketch of it. In my example is very easy to imagine... the lines up and down (without and with) that can be together of 2nd dimension image aspects can be exemplified so:


Organizing the layers on Gimp.

The sequence of layer is ordered by the first dimension aspects and applied in the aspects of the 2nd dimension:

First aspect of 1st dimension

1st layer: 1st aspect of 2nd dim (hyphen dash lines) without lines up and down. =&gt; 0°
2rd layer: 2nd aspect of 2nd dim (point dash lines) without lines up and down. =&gt; 90°
3th layer: 3rd aspect of 2nd dim (slash lines) without lines up and down. =&gt; 180°
4th layer: 4th aspect of 2nd dim (backslash lines) without lines up and down. =&gt; 270° | -90°

Second aspect of 1st dimension

5nd layer: 1st aspect of 2nd dim (hyphen dash lines) with lines up and down. =&gt; 0
6th layer: 2nd aspect of 2nd dim (point dash lines) with lines up and down. =&gt; 90°
7th layer: 3rd aspect of 2nd dim (slash lines) with lines up and down. =&gt; 180°
8th layer: 4th aspect of 2nd dim (backslash lines) with lines up and down. =&gt; 270° | -90°


We need organize the layer by groups, those of 1st dimension and 2nd dimension.
Explained in another way the general rule is:

Groups of 1st dimension = Total layers / 1st dimension aspects = Layers per group
Will be 8/2=4 =&gt; this imply that we have 2 groups with 4 layers (the are the aspects of 2nd dimension).

Each group of 1st dimension is divided by the number of aspects of the 2nd dimension, in this case 4/4=1, then we have one layer for each angular position, in total 4.

How it works
The first dimension is Random, so the aspects of 2nd dimension will be printed randomly, without or with the lines up-down, in all aspects of 2nd dimension:

- - - | . . . | / / /  | \ \ \

The 2nd dimension is Angular, so the aspects are printed following the angular variation of stylus… in my gih matrix example this behavior have only 4 states &gt; 0, 90, 180 and 270°. Then the aspects

- - - correspond to 0°;

. . . to 90°;&nbsp;

\ \ \ to 180° and&nbsp;

/ / / to 270° = -90°.



The gih array for angular behavior on gimp begins always with 90° layers, in my example are the 2nd and 6th layers.


Sample of tests with gih matrix brush.

The array isn’t very precise with a short numbers of ranks to angular behavior… but is sufficient to use in the major part the correct stain aspects.


Angular precision of angular gih with more steps.



This sample was made with 8 layers… with 45° steps, is possible to see that the angular behavior precision depends by number of layers.
Sample only to make a sample ;-)

The brush is not created to drawing or painting… only to make a practical example of a 2 dimensions gih matrix, but the even so I’ve made a sample ;)


A few samples with the gih matrix brush example... only to have a picture ;-)


Conclusions
I’ve been making gih brushes since 2008… and the gih matrix is a thing very difficult to understand… you need to be a developer or a mathematician ;-) I don’t know but I’ve studied this matrix many times in different periods… and is always a bit complex to remember all aspects. Then I thought to write this document, to make a big picture to help decide when we can to use this resource. In past, very recent, I was bit convict that don’t have sense the gih brushes with more that 1 dimension… but was a question of my difficult to understand how to use and make them an easy way.

The main reason to make a gih brush with more than 1 dimension is related with some nuances of the stains, per example, in the series Variety I think very interesting to have a small random noise on the border of line strokes… but each case is a case… sometimes is better have only a gbr or a simple gih with only 1 dimension.

References
Video about Gimp Gih matrix - Dimensions versus Aspects
The Gih Dialog Box