add rotation, need more tests

.gitignore

@@ -9,4 +9,10 @@
 spirale
 starfield
 randomwalk
+oscilloscope
+lissajous
+squarmania
+testbed
+rndwlkng
+morecircles
 

Makefile

@@ -1,27 +1,92 @@
+#
 
-all:		spirale.png
+all:		testbed
 
 # -----------------------------------------------
 
 genplotting.o:	genplotting.f90 Makefile
 	gfortran -Wall -c $< 
 
+genp_tests.o:	genp_tests.f90 genplotting.o Makefile
+	gfortran -Wall -c $< 
+
+testbed:	testbed.f90 Makefile genp_tests.o genplotting.o
+	gfortran -Wall $< genplotting.o genp_tests.o -o $@
+
+# -----------------------------------------------
+
+rndwlkng:	rndwlkng.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
+rndwlkng.png:	rndwlkng Makefile
+	./rndwlkng
+	convert rndwlkng.tga rndwlkng.png
+
+# -----------------------------------------------
+
+morecircles:	morecircles.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
+morecircles.png:	morecircles Makefile
+	./morecircles
+	convert morecircles.tga morecircles.png
+
 # -----------------------------------------------
 
 starfield:	starfield.f90 Makefile genplotting.o
 	gfortran -Wall $< genplotting.o -o $@
 
+starfield.png:	starfield Makefile
+	./starfield
+	convert -verbose WS/a.tga $@
+
+# -----------------------------------------------
+
 randomwalk:	randomwalk.f90 Makefile genplotting.o
 	gfortran -Wall $< genplotting.o -o $@
 
+randomwalk.png:	randomwalk Makefile
+	./randomwalk
+	genplot2 -s 512x512 WS/randomwalk.scratch WS/a.tga
+	convert WS/a.tga $@
+
+# -----------------------------------------------
+
+oscilloscope:	oscilloscope.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
+oscilloscope.png:	oscilloscope Makefile
+	./oscilloscope
+	genplot2 -s 512x512 WS/oscilloscope.scratch WS/a.tga
+	convert WS/a.tga $@
+
 # -----------------------------------------------
 
 spirale:	spirale.f90 Makefile genplotting.o
 	gfortran -Wall $< genplotting.o -o $@
 
 spirale.png:	spirale Makefile
-	./spirale > s.scratch
-	genplot2 -s 512x512 s.scratch a.tga
-	convert a.tga $@
+	./spirale
+	convert WS/a.tga $@
+
+# -----------------------------------------------
+
+lissajous:	lissajous.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
+lissajous.png:	lissajous Makefile
+	./lissajous
+	genplot2 -s 512x512 WS/lissajous.scratch WS/a.tga
+	convert WS/a.tga $@
+
+# -----------------------------------------------
+
+squarmania:	squarmania.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
+squarmania.png:	squarmania Makefile
+	./squarmania
+	genplot2 -s 512x512 WS/squarmania.scratch WS/a.tga
+	convert WS/a.tga $@
 
 # -----------------------------------------------

README.md

@@ -2,11 +2,16 @@
 
 Voici quelques tentatives de dessins inutiles réalisés avec du
 [Fortran moderne](https://fortran-lang.org/fr/learn/), et quelques
-morceaux de C parce que *why not ?*
+morceaux de C parce que *why not ?* L'idée générale c'est d'utiliser
+de la basse technologie (traduction hasardeuse de **lowtech**) pour
+servir la noble cause de la
+[techno-futilité](https://wiki.interhacker.space/index.php?title=Techno-futilit%C3%A9).
 
-Un peu de lecture : [utilisation](usage.md) et [exemples](exemples.md).
+Un peu de lecture : [license](LICENSE), [utilisation](usage.md) et
+[exemples](exemples.md).
 
-Vous pouvez suivre le croisimot [#UselessGraphic](https://mastodon.tetaneutral.net/tags/uselessgraphic)
+Vous pouvez suivre le croisimot
+[#UselessGraphic](https://pleroma.interhacker.space/tag/uselessgraphic)
 dans le grand Ternet sauvage. Pour me contacter, il faut utiliser les
 [méthodes](https://www.tetalab.org/fr/contact) habituelles du Tetalab.
 

WS/README.md

@@ -0,0 +1,3 @@
+# This is the work space.
+
+Used to store work files, like `a.scratch` plotting directives.

docs/exemples.md

@@ -0,0 +1,24 @@
+# Genplotting exemples
+
+## Spiral
+
+Source code: [spirale.f90](../spirale.f90) / if you change the parameter
+in the call to `do_spirale`, you can see some nice variations on the
+spiraling thing.
+
+![#UselessGraphic : la spirale](../picz/spirale.png)
+
+This was my first testbed for this new *disruptive* technology, but
+there was so many variations of spirales, and i'm thinking about
+a powerfull spiral generator. *Stay tuned, film at 11*.
+
+## Dessins numériques
+
+By the way, I'm using all that *futilo-technology* for trying to
+make some
+[numeric pictures](http://maison.tth.netlib.re/dessins/numerique.html)
+(aka #UselessGraphic). I try to use various mathematic fundations, and
+I hack and divert and modify and ignore all that for just make
+[UselessGraphic](https://mastodon.tetaneutral.net/tags/uselessgraphic).
+*Feel free to share and enjoy*.
+

docs/usage.md

@@ -0,0 +1,53 @@
+# Usage
+
+The genplotting library use, as a backend, an external 
+[software](https://git.tetalab.org/tTh/libtthimage/src/branch/master/Tools/genplot2.c)
+who can be installed with the [libtthimage](https://git.tetalab.org/tTh/libtthimage) and convert scratchfiles to
+[Targa](https://en.wikipedia.org/wiki/Truevision_TGA) image file. 
+
+For drawing an *useless graphic*, you have to follow three steps:
+initialize, use and terminating.
+You can look at some [examples](exemples.md) and at a
+[full page](http://maison.tth.netlib.re/dessins/numerique.html)
+off UselessGraphics.
+
+## Initialize
+
+Call the subroutine `genp_init` with two parameters.
+The first is an integer and must be 0. In the futur, it may be used for
+setting some predefined configurations. 
+ 
+The second is the filename for recording the plottings instructions,
+I'm using the `.scratch` extension for naming this file.
+And if this filename is an empty string, *stdout* will be used, so
+you can pipe the data for post-processing purpose.
+ **Be warned:** if you use this option, don't write anything to the
+unit 6 **!**
+
+## Use it
+
+- `real xa, ya, xb, yb`
+- `integer color`
+- `call genp_move(xa, ya)`
+- `call genp_draw(xa, ya, color)`
+- `call genp_line(xa, ya, xb, yb, color)`
+
+## Terminator
+
+- `call genp_end(0)`
+This procedure end the current plotting, add some *bells* to the *WIP*,
+and close the output file, if an output file was specified.
+
+## Rendering
+
+- `subroutine genp_do_render(srcfile, tgafile, xsize, ysize)`
+
+After doing all that useless computing graphics, you can call
+the render, only if you have given a filename to `genp_init`.
+The render engine that I use can only write Targa file, but
+I'm going to add `PNG` to it output in a near futur.
+
+
+
+
+

exemples.md

@@ -1,21 +0,0 @@
-# Genplotting exemples
-
-## Spiral
-
-Code source : [spirale.f90](spirale.f90) / if you change the parameter
-in the call to `do_spirale`, you can see some nice variations on the
-spiraling thing.
-
-![#UselessGraphic : la spirale](picz/spirale.png)
-
-This was my first testbed for this new *disruptive* technology, but
-there was so many variations of spirales, and i'm thinking about
-a powerfull spiral generator. *Stay tuned, film at 11*.
-
-## Dessins numériques
-
-Et donc, j'utilise toute cette futilo-technologie pour essayer de
-faire des
-[dessins numériques](http://maison.tth.netlib.re/dessins/numerique.html) 
-en expliquant ma démarche de création et d'autres vagues pensées qui
-me passent par la tête. 

genp_tests.f90

@@ -0,0 +1,41 @@
+!
+!           MODULE FOR TESTING THE GENPLOTTING MODULE
+!
+! this crapware is released by tTh under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
+! new Sun May 17 11:21:39 AM UTC 2026
+
+module genp_tests
+  use genplotting
+  implicit none
+  contains
+! ---------------------------------------------------------
+subroutine genp_test_rotation()
+
+  real             :: mat(3, 3)
+  real             :: pta(3), ptb(3)
+  integer                :: pass, i, j
+  
+  write(0, '("*** TEST ROTATION ***")' )
+  do pass=1, 90
+    call genp_set_rotation (real(pass)*0.10)
+    write(0, *) "  * the matrix was : "
+    call genp_get_rot_matrix(mat)
+    do i=1, 3
+      do j=1, 3
+        write (0, '("   ", F8.5)', advance='no') mat(i,j)
+      end do
+      write(0, *)
+    end do
+
+    call genp_move(0.0, 0.0)
+    pta(1) = 11.0   ;   pta(2) = 0.0   ;   pta(3) = 0.0
+    ptb = matmul(mat, pta)
+    write(0, '(" got XY: ", F8.5, " ", F8.5)') ptb(1), ptb(2)
+    call genp_draw(ptb(1), ptb(2), 1+mod(pass, 7))
+  end do   ! pass
+
+end subroutine
+! ---------------------------------------------------------
+end module

genplotting.f90

@@ -11,15 +11,30 @@ module genplotting
   real      ::    xoffset, yoffset, xscale, yscale
   private   ::    xoffset, yoffset, xscale, yscale
 
-  integer   ::    outunit
+  real      ::    rotation, rotmatrix(3,3)
+  private   ::    rotation, rotmatrix, compute_rot_matrix
+  private   ::    print_rot_matrix
+
+  integer   ::    outunit = 6
   private   ::    outunit
 
 contains
 ! ---------------------------------------------------------
+! the first parameter _must_ be 0.
+! the second can be
+!    - the name of a file for recording plot instructions
+!  or
+!    - an empty string for send plot command to stdout
+!
 subroutine genp_init (foo, fname)
   integer, intent(in)             :: foo
   character (len=*), intent(in)   :: fname
 
+  IF (FOO .NE. 0)   THEN
+    WRITE(0, '("FOO .NE. 0")')
+    CALL EXIT(1) 
+  END IF
+
   outunit = 6          ! stdout
   if (len(fname) .gt. 0) then
     write (0, '("genplot init opening : ", A)') fname
@@ -29,7 +44,10 @@ subroutine genp_init (foo, fname)
   xmin = 9e9       ;       xmax = -9e9
   ymin = 9e9       ;       ymax = -9e9
   xoffset = 0.0    ;       yoffset = 0.0
-  xscale  = 0.0    ;       yscale  = 0.0
+  xscale  = 1.0    ;       yscale  = 1.0
+
+  rotation = 0.0
+
 end subroutine
 ! ---------------------------------------------------------
 subroutine genp_set_offset(ox, oy)
@@ -41,10 +59,71 @@ subroutine genp_get_offset(ox, oy)
   ox = xoffset      ;      oy = yoffset
 end subroutine
 ! ---------------------------------------------------------
+! new Tue May 12 06:51:57 PM UTC 2026
+subroutine genp_set_scale(sx, sy)
+  real, intent(in)     :: sx, sy
+  xscale = sx      ;      yscale = sy
+end subroutine
+subroutine genp_get_scale(sx, sy)
+  real, intent(out)     :: sx, sy
+  sx = xscale      ;      sy = yscale
+end subroutine
+! ---------------------------------------------------------
+! this is a private procedure, don't call it from your prog
+subroutine compute_rot_matrix(angle)
+  real, intent(in)    :: angle
+  write (0, '("compute rot matrix for", F8.5, " radians")') &
+                                     angle
+  rotmatrix (1, 1) =  cos(angle)
+  rotmatrix (1, 2) =  sin(angle)
+  rotmatrix (1, 3) =  0.0
+
+  rotmatrix (2, 1) = -sin(angle)
+  rotmatrix (2, 2) =  cos(angle)
+  rotmatrix (2, 3) =  0.0
+
+  rotmatrix (3, 1) =  0.0
+  rotmatrix (3, 2) =  0.0
+  rotmatrix (3, 3) =  1.0
+
+end subroutine
+!                  -----------------
+!    we have computed some fancy numbers
+!                      and we want to see them !
+subroutine print_rot_matrix(fd)
+  integer, intent(in)    :: fd
+
+  integer                :: i, j
+  do i=1, 3
+    do j=1, 3
+      write (fd, '("   ", F8.5)', advance='no') rotmatrix(i,j)
+    end do
+    write(fd, *)
+  end do
+end subroutine
+! ---------------------------------------------------------
+subroutine genp_set_rotation(angle)
+  real, intent(in)     :: angle
+  rotation = angle
+  !       compute the matrix here !
+  call compute_rot_matrix(angle)
+  ! call print_rot_matrix(0)
+end subroutine
+
+real function genp_get_rotation()
+  genp_get_rotation = rotation
+end function
+
+subroutine genp_get_rot_matrix (dst)
+  real, intent(out)   :: dst(3, 3)
+  dst = rotmatrix
+end subroutine
+! ---------------------------------------------------------
 subroutine genp_move (px, py)
   real, intent(in)        :: px, py
   real                    :: lx, ly
-  lx = px + xoffset     ;     ly = py + yoffset
+  lx = (px*xscale) + xoffset
+  ly = (py*yscale) + yoffset
   write (outunit, '(2F12.5, I5)') lx, ly, -1
   if (lx .lt. xmin)      xmin = lx
   if (lx .gt. xmax)      xmax = lx
@@ -56,7 +135,8 @@ subroutine genp_draw (px, py, color)
   real, intent(in)        :: px, py
   integer, intent(in)     :: color
   real                    :: lx, ly
-  lx = px + xoffset     ;     ly = py + yoffset
+  lx = (px*xscale) + xoffset
+  ly = (py*yscale) + yoffset
   write (outunit, '(2F12.5, I5)') lx, ly, color
   if (lx .lt. xmin)      xmin = lx
   if (lx .gt. xmax)      xmax = lx
@@ -71,18 +151,54 @@ subroutine genp_line(xa, ya, xb, yb, color)
   call genp_draw(xb, yb, color)
 end subroutine
 ! ---------------------------------------------------------
+subroutine genp_plot_axes(amp)
+  real, intent(in)     :: amp
+  call genp_move(0.0, -amp)
+  call genp_draw(0.0,  amp, 7)
+  call genp_move(-amp, 0.0)
+  call genp_draw( amp, 0.0, 7)
+end subroutine
+! ---------------------------------------------------------
+subroutine genp_circle(radius, steps, color)
+  real, intent(in)      :: radius
+  integer, intent(in)   :: steps, color
+
+  integer               :: idx
+  real                  :: fk, ang, x, y
+  logical               :: firstdot
+
+  if (steps .LT.3 ) then
+    write(0, '("circle: steps ", I3, " bad value")') steps
+    return
+  endif
+
+  firstdot = .TRUE.
+  do idx=0, steps
+    fk = real(idx) / real(steps)
+    ang = 6.283185307 * fk
+    ! write(0, '(I5, "  ->  ", 2F10.5)') idx, fk, ang
+    x = radius * cos(ang)   ;   y = radius * sin(ang)
+    if (firstdot) then
+      call genp_move(x, y)   ;    firstdot = .FALSE.
+    else
+      call genp_draw(x, y, color)
+    endif
+  enddo
+
+end subroutine
+! ---------------------------------------------------------
 subroutine genp_end (foo)
   integer, intent(in)    :: foo
 
-  write (0, '("--- genp_end ---")')
-  write (0, '("minmax X", 2F16.5)') xmin, xmax
-  write (0, '("minmax Y", 2F16.5)') ymin, ymax
+  write (0, '("------------- genp_end -------------")')
+  write (0, '("minmax X ", 2F18.5)') xmin, xmax
+  write (0, '("minmax Y ", 2F18.5)') ymin, ymax
 
-  write (outunit, '(2F16.5, I6)') xmin*1.05, ymin*1.05, -1
-  write (outunit, '(2F16.5, I6)') xmin*1.05, ymax*1.05,  0
-  write (outunit, '(2F16.5, I6)') xmax*1.05, ymax*1.05,  0
-  write (outunit, '(2F16.5, I6)') xmax*1.05, ymin*1.05,  0
-  write (outunit, '(2F16.5, I6)') xmin*1.05, ymin*1.05,  0
+  write (outunit, '(2F18.5, I6)') xmin*1.05, ymin*1.05, -1
+  write (outunit, '(2F18.5, I6)') xmin*1.05, ymax*1.05,  0
+  write (outunit, '(2F18.5, I6)') xmax*1.05, ymax*1.05,  0
+  write (outunit, '(2F18.5, I6)') xmax*1.05, ymin*1.05,  0
+  write (outunit, '(2F18.5, I6)') xmin*1.05, ymin*1.05,  0
   close (outunit)
 
   if (6 .ne. outunit) then
@@ -91,6 +207,46 @@ subroutine genp_end (foo)
 
 end subroutine
 ! ---------------------------------------------------------
+!                  /!\  warning /!\
+!    this procedure is highly experimental, don't use it
+!    for any real (or critical) work, but it was fine for
+!    playing around with the #UselessGraphic concept.
+
+subroutine genp_do_render(srcfile, tgafile, xsize, ysize)
+  character (len=*), intent(in)   :: srcfile, tgafile
+  integer, intent(in)             :: xsize, ysize
+
+  character (len=1664)            :: cmdline
+  character (len=20)              :: dima, dimb
+  integer                         :: i, j, errcode
+
+  if  (6 .EQ. outunit) then
+    write(0, '(" Sorry, I can not do that, Dave !")')
+    stop " >>> FATAL ERROR"
+  endif
+
+  write(0, '("--- genp do_render ---")')
+  write(0, '("    srcfile: ", A)') srcfile
+  write(0, '("    tgafile: ", A)') tgafile
+  write(0, '("    picsize: ", 2I5)') xsize, ysize
+
+  write(dima, '(I5, "x", I5)') xsize, ysize
+  ! write(0, '("dima [",A, "]")') dima
+  dimb = ""   ;   j = 1
+  do i=1, len(dima)
+    if (dima(i:i) .NE. ' ') then
+      dimb(j:j) = dima(i:i)
+      j = j +1
+    endif
+  enddo
+  ! write(0, '("[",A, "]")') trim(dimb)
+  write(cmdline, '("genplot2 -s ", A, " ", A, " ", A)') &
+                          trim(dimb), srcfile, tgafile
+  write(0, '(A)') trim(cmdline)
+  call execute_command_line(cmdline, exitstat=errcode)
+  write(0, '("errcode was :", I6)') errcode
+
+end subroutine
 ! ---------------------------------------------------------
 
 end module genplotting

lissajous.f90

@@ -0,0 +1,41 @@
+program sinwaves
+  use genplotting
+  implicit none
+
+  integer  foo, c
+  real     phase
+  call genp_init (0, 'WS/lissajous.scratch')
+
+  do foo=1, 20
+    phase = real(foo) * 0.314159
+    c = 3 + mod(foo, 2)
+    call do_lissajous (400, phase, c)
+  enddo
+
+  call genp_end (0)
+
+contains
+! ---------------------------------------------------------
+subroutine do_lissajous (nbpass, phy, col)
+  integer, intent(in)   :: nbpass, col
+  real,    intent(in)   :: phy
+
+  integer               :: idx
+  real                  :: ridx, x, y
+
+  do idx=0, nbpass
+    ridx = 6.28318 * (real(idx) / real(nbpass))
+    x = sin(ridx + phy)
+    y = cos(ridx*3)
+
+    if (idx .eq. 0) then
+      call genp_move(x, y)
+    else
+      call genp_draw(x, y, col)
+    endif
+
+  enddo
+
+end subroutine
+! ---------------------------------------------------------
+end program

morecircles.f90

@@ -0,0 +1,28 @@
+!
+!           YOU LIKE CIRCLES ? TAKE IT SISTA !
+!
+! this crapware is released by tTh under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
+
+program morecircles
+  use genplotting
+  implicit none
+  integer     idx
+  real        fdx, xp, yp, scx, scy
+  call genp_init(0, "WS/morecircles.scratch")
+  scx = 0.6   ;   scy = 2.3
+  do idx=5, 60
+    fdx = real(idx)
+    xp = 3.5 * cos((fdx/14.0)-0.7)
+    yp = 3.5 * sin((fdx/10.0)+0.3)
+    call genp_set_offset(xp, yp)
+    call genp_set_scale(scx, scy)
+    call genp_circle(fdx, 60, 1+mod(idx, 3))
+    scx = scx + 0.0185
+    scy = scy - 0.0129
+  enddo
+  call genp_end(0)
+  call genp_do_render("WS/morecircles.scratch", "morecircles.tga", &
+                   512, 512)
+end program

oscilloscope.f90

@@ -0,0 +1,69 @@
+!
+!                    OSCILLOSCOPE EXPERIMENT
+!
+! this crapware is released by tTh under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
+program oscilloscope
+  use genplotting
+  implicit none
+
+  real, dimension(4)    :: frequences
+
+  write (0, '(A)') "----[ genplotting oscilloscope ]----"
+  call srand(time())
+  call genp_init (0, 'WS/oscilloscope.scratch')
+
+  frequences(1) = 24.86
+  frequences(2) = 29.77
+  frequences(3) = 37.56
+  frequences(4) = 49.3
+
+  call do_oscilloscope(frequences, 2)
+
+  call genp_end (0)
+contains
+! ---------------------------------------------------------
+real function compute_a_value(clk, freq, phase)
+  real, intent(in)    :: clk, freq, phase
+  real                :: v, f
+  f = freq*(clk+phase)
+  v = sin(f) + (0.3 * sin(3*f)) + (0.1 * sin(5*f))
+  compute_a_value = v
+end function
+! ---------------------------------------------------------
+subroutine plot_a_trace(freq, phy, nbsteps, ypos, col)
+  real, intent(in)        :: freq, phy, ypos
+  integer, intent(in)     :: nbsteps, col
+
+  integer          idx
+  real             rstep, px, py
+  logical          firstdot
+
+  firstdot = .TRUE.
+  do idx=0, nbsteps
+    rstep = (real(idx)/real(nbsteps)) 
+    px    = -10.0 + (20.0 * rstep)
+    py = ypos + compute_a_value (rstep, freq, phy)
+    if (firstdot) then
+      call genp_move(px, py)   ;   firstdot = .false.
+    else
+      call genp_draw(px, py, col)
+    endif
+  enddo
+
+end subroutine
+! ---------------------------------------------------------
+subroutine do_oscilloscope(freqs, col)
+  real, intent(in), dimension(4)   :: freqs
+  integer, intent(in)              :: col
+
+  call plot_a_trace(freqs(1), 0.2, 120,  6.66, col)
+  call plot_a_trace(freqs(2), 1.0, 120,  3.33, col)
+  call plot_a_trace(freqs(3), 2.6, 120, -3.33, col)
+  call plot_a_trace(freqs(4), 3.1, 120, -6.66, col)
+  call genp_plot_axes(10.0)
+
+end subroutine
+! ---------------------------------------------------------
+end program

randomwalk.f90

@@ -7,15 +7,19 @@ program randomwalk
   use genplotting
   implicit none
   integer    foo, col
-
+  real       px, py
   write (0, '(A)') "----[ genplotting randomwalk ]----"
   call srand(time())
-  call genp_init (0, 'randomwalk.scratch')
-  do foo=1, 51
-    col = 2 + mod(foo, 4)
-    call do_randomwalk(42, col)
+  call genp_init (0, 'WS/randomwalk.scratch')
+  do foo=1, 20
+    px = 100 * (rand(0) - 0.50)
+    py = 100 * (rand(0) - 0.50)
+    call genp_set_offset(px, py)
+    col = 1 + mod(foo, 6)
+    call do_randomwalk(500, col)
   enddo
   call genp_end (0)
+  stop
 contains
 ! ---------------------------------------------------------
 subroutine do_randomwalk(nbre, col)
@@ -23,14 +27,14 @@ subroutine do_randomwalk(nbre, col)
   integer                     :: idx
   real                        :: px, py, px2, py2
 
-  px = 0.0        ;       py = 0.0
-  call genp_move(px, py)
+  px = 0.0    ;    py = 0.0
   do idx=1, nbre
     px2 = px + rand(0) - 0.50
     py2 = py + rand(0) - 0.50
     call genp_line(px, py, px2, py2, col)
     px = px2  ;  py = py2
   enddo
+
 end subroutine
 ! ---------------------------------------------------------
 end program

rndwlkng.f90

@@ -0,0 +1,61 @@
+!
+!               Random Walk Next Generation
+!           new Fri May  8 06:53:02 AM UTC 2026
+!
+! this crapware is released by tTh under the
+!               DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
+! ---------------------------------------------------------
+program rndwlkng
+  use genplotting
+  implicit none
+
+  type walker
+    real    :: xloc, yloc      ! where I am ?
+    real    :: heading         ! direction in degrees
+    real    :: powa            ! correlated to nothing
+  end type walker
+
+  type (walker)  drunky
+  integer        pass
+
+  call srand(time())
+
+  call genp_init(0, "WS/rndwlkng.scratch")
+
+  do pass=1, 73
+    drunky%xloc     =  5555 * (rand(0) - 0.50)
+    drunky%yloc     =  5555 * (rand(0) - 0.50)
+    drunky%heading  =   360 * rand(0)
+    drunky%powa     =  6.00
+    call move_the_walker(drunky, 700, mod(pass, 6)+1)
+  end do
+
+  call genp_end(0)
+  call genp_do_render("WS/rndwlkng.scratch", "rndwlkng.tga", 512, 512)
+
+contains
+! ---------------------------------------------------------
+subroutine move_the_walker(bob, nbmove, col)
+  type (walker), intent(inout)  :: bob
+  integer, intent(in)           :: nbmove, col
+
+  integer                       :: idx
+  real                          :: rad, mv, dx, dy
+
+  call genp_move(bob%xloc, bob%yloc)
+  do idx=1, nbmove
+    rad = ( 3.141592654 * bob%heading ) / 180.0
+    mv = 1.555 + (bob%powa * rand(0))
+    dx = mv * sin(rad)
+    dy = mv * cos(rad)   
+    bob%xloc = bob%xloc + dx    
+    bob%yloc = bob%yloc + dy    
+    bob%heading = bob%heading + 42.42 * (rand(0) - 0.50000)
+    call genp_draw(bob%xloc, bob%yloc, col)
+  enddo
+
+end subroutine
+! ---------------------------------------------------------
+end program
+! ---------------------------------------------------------

spirale.f90

@@ -1,32 +1,39 @@
+!
 !                    SPIRALING...
 ! new Thu Apr 23 04:27:03 PM UTC 2026
 !
-
+! this crapware is released under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
 program spirale
   use genplotting
   implicit none
 
+  character(*), parameter :: scratch = "WS/spirale.scratch"
+
   write (0, '(A)') "----[ genplotting spirale ]----"
 
-  call genp_init (0, 's.scratch')
-  call do_spirale (1337)
+  call genp_init (0, scratch)
+  call do_spirale (1337, 0.51, 0.0666, 0.7, 5)
+  call do_spirale (1337, 0.42, 0.0333, 0.7, 6)
   call genp_end (0)
+  call genp_do_render(scratch, "WS/a.tga", 512, 512)
 
 contains
 ! ---------------------------------------------------------
-subroutine do_spirale (nbpass)
-  integer, intent(in)     :: nbpass
-  integer         idx, col
+subroutine do_spirale (nbpass, kdist, krad, phy, col)
+  integer, intent(in)     :: nbpass, col
+  real,    intent(in)     :: kdist, krad, phy
+  integer         idx
   real            rad, px, py, dist
 
   px = 0.0 ; py = 0.0
   call genp_move (px, py)
   do idx=1, nbpass
-    dist = real(idx) * 0.51
-    rad = real(idx) * 0.0666
+    dist = real(idx) * kdist
+    rad  = (real(idx) * krad) + phy
     px = dist * sin(rad)
     py = dist * cos(rad)
-    col = 3
     call genp_draw (px, py, col)
   enddo
 end subroutine

squarmania.f90

@@ -0,0 +1,50 @@
+!
+!                    SQUARMANIA
+!       new Thu Apr 23 04:27:03 PM UTC 2026
+!
+! this crapware is released by tTh under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
+program squarmania
+  use genplotting
+  implicit none
+
+  write (0, '(A)') "----[ genplotting squarmania ]----"
+
+  call genp_init (0, 'WS/squarmania.scratch')
+  call do_squarmania (40, 0.934)
+  call genp_end (0)
+
+contains
+! ---------------------------------------------------------
+subroutine do_squarmania (nbr, k0)
+  integer, intent(in)   :: nbr
+  real, intent(in)      :: k0
+
+  integer    :: idx
+  real       :: xa, xb, xc, xd, ya, yb, yc, yd
+  real       :: va, vb, vc, vd, wa, wb, wc, wd, k2
+
+  k2 = 1.0 - k0
+  xa =  1  ; ya =  1    ;   xb =  1  ; yb = -1
+  xc = -1  ; yc = -1    ;   xd = -1  ; yd =  1
+
+  do idx=1, nbr
+    call genp_move(xa, ya)
+    call genp_draw(xb, yb, 1)  ; call genp_draw(xc, yc, 1)
+    call genp_draw(xd, yd, 2)  ; call genp_draw(xa, ya, 2)
+
+    va = k0*xa + k2*xb         ;  wa = k0*ya + k2*yb
+    vb = k0*xb + k2*xc         ;  wb = k0*yb + k2*yc
+    vc = k0*xc + k2*xd         ;  wc = k0*yc + k2*yd
+    vd = k0*xd + k2*xa         ;  wd = k0*yd + k2*ya
+
+    xa = va ; xb = vb ; xc = vc ; xd = vd
+    ya = wa ; yb = wb ; yc = wc ; yd = wd
+
+  enddo
+
+end subroutine
+
+! ---------------------------------------------------------
+end program

starfield.f90

@@ -1,24 +1,35 @@
 !
 !         BUILD A STAR FIELD
+
+! this crapware is released by tTh under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
 !
 program starfield
   use genplotting
   implicit none
+
+  character(*), parameter :: scratch = "WS/starfield.scratch"
+
   write (0, '(A)') "----[ genplotting starfield ]----"
-  call genp_init (0, 'starfield.scratch')
-  call do_starfield (451)
+  call genp_init (0, scratch)
+  call do_starfield (300)
   call genp_end (0)
+  call genp_do_render(scratch, "WS/a.tga", 512, 512)
+
 contains
 ! ---------------------------------------------------------
 subroutine plot_a_star(at_x, at_y, sz, color)
   real, intent(in)        :: at_x, at_y, sz
   integer, intent(in)     :: color
+
   integer                 :: idx
   real                    :: rad, xv, yv
-  write(0, '("plot a star ", 2F8.3)') at_x, at_y
+
+  write(0, '("plot a star at ", 2F8.3)') at_x, at_y
   call genp_set_offset(at_x, at_y)
   do idx=0, 360, 36
-    rad = 0.042 + (real(idx) * (3.14159 / 180))
+    !   convert index to radians
+    rad = real(idx) * (3.14159 / 180)
     xv = sz * sin(rad)    ;    yv = sz * cos(rad)
     call genp_move(0.0, 0.0)
     call genp_draw(xv, yv, color)
@@ -27,12 +38,13 @@ end subroutine
 ! ---------------------------------------------------------
 subroutine do_starfield (nbstar)
   integer, intent(in)     :: nbstar
+
   integer         idx, color
   real            px, py, sz
   do idx=1, nbstar
     px = (rand(0) * 10.00) - 5.00
     py = (rand(0) * 10.00) - 5.00
-    sz = (rand(0) *  0.16) + 0.16
+    sz = (rand(0) *  0.30) + 0.12
     color = 1 + mod(idx, 7)
     call plot_a_star(px, py, sz, color)
   end do

testbed.f90

@@ -0,0 +1,18 @@
+!
+!           TESTBED FOR GENPLOTTING90
+!
+! this crapware is released by tTh under the
+!             DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
+!
+
+program testbed
+  use genplotting
+  use genp_tests
+  implicit none
+
+  call genp_init(0, "foo.scratch")
+  call genp_test_rotation()
+  ! call genp_plot_axes(5.1)
+  call genp_end(0)
+
+end program

usage.md

@@ -1,27 +0,0 @@
-# Usage
-
-The genplotting library use, as a backend, an external 
-[software](https://git.tetalab.org/tTh/libtthimage/src/branch/master/Tools/genplot2.c)
-who can be installed with the [libtthimage](https://git.tetalab.org/tTh/libtthimage) and convert scratchfiles to
-[Targa](https://en.wikipedia.org/wiki/Truevision_TGA) image file. 
-
-Three steps : initialize, use and terminating.
-
-## Initialize
-
-Call the subroutine `genp_init` with two parameters.
-The first is an integer and must be 0. 
-The second is the filename for recording the plottings instructions,
-if this filename is an empty string, *stdout* will be used.
-
-## Use it
-
-- call genp_move(x, y)
-- call genp_draw(x, y, c)
-
-## Terminator
-
-- call genp_end(0)
-
-
-