first real run, make a gif89a, need more tweaking

GravityField/.gitignore

@@ -1,6 +1,10 @@
 
 essai
 
+WS/*.pgm
+
+*.gif
+
 foo.pgm
 bar.pgm
 

GravityField/Makefile

@@ -2,7 +2,8 @@
 #    Fortraneries by tTh - Gravity Field
 #
 
-GFOPT = -Wall -Wextra -g -time 
+GFOPT   = -Wall -Wextra -g -time -pg -I../Modules
+MODOBJ  = '../Modules/spitpgm.o'
 
 all:	essai
 
@@ -10,6 +11,6 @@ realfield.o:	realfield.f90 Makefile
 	gfortran $(GFOPT) -c $<
 
 essai:	essai.f90  Makefile realfield.o
-	gfortran $(GFOPT) $< realfield.o -o $@
+	gfortran $(GFOPT) $< realfield.o $(MODOBJ) -o $@
 
 

GravityField/essai.f90

@@ -1,54 +1,97 @@
+!-----------------------------------------------------------------------
 !
 !       project "gravity field"
 !
+!-----------------------------------------------------------------------
 program essai
   use realfield
+  use spitpgm               ! XXX
+
   implicit none
 
   type(massbody)          :: planet
   integer                 :: foo
-  planet%posx = 1337.314
+  character (len=100)     :: filename
-  planet%posy = 1664.666
-  planet%mass = 1e4
 
-  do foo=1, 10
+  planet%posx   = 337.314
-    call build_a_field(800, 600, planet)
+  planet%posy   = 164.666
-    planet%posy = planet%posy + 51.45
+  planet%mass   = 1e8
+  planet%serial = 42
+
+  do foo=0, 48
+    write (filename, "(a, i5.5, a)") 'WS/', foo, '.pgm'
+    call build_and_write_a_field(800, 600, planet, filename)
+    planet%posx = planet%posx + 6.99
+    planet%posy = planet%posy + 2.55
   enddo
 
   STOP 'YOLO'
 
-contains        !------------------------------------------
+contains
-!
+!-----------------------------------------------------------------------
-subroutine build_a_field(szx, szy, moon)
+!-
+!   compute a field with only one body; and write pic file
+!-
+subroutine build_and_write_a_field(szx, szy, moon, fname)
   integer, intent(in)                :: szx, szy
   type(massbody), intent(in)         :: moon
+  character (len=*), intent(in)      :: fname
 
-  integer                            :: ix, iy
+  real                               :: maxi, mini
-  real                               :: fx, fy
-  real                               :: grav, maxi, mini
   integer                            :: errcode
   real,    dimension(:,:), allocatable  :: field
+  integer, dimension(:,:), allocatable  :: greymap
 
   allocate(field(szx, szy), stat=errcode)
 
-  do ix=1, szx
+  call compute_a_field(field, moon)
-    fx = real(ix)
-    do iy=1, szy
-      fy = real(iy)
-      grav = compute_gravity(ix, iy, moon) / 2180800.0
-      field(ix,iy) = grav
-    enddo
-  enddo
-
   maxi = maxval(field)
   mini = minval(field)
   print *, "field: ", mini, maxi, maxi-mini
 
+  allocate(greymap(szx, szy), stat=errcode)
+  greymap = 65535
+  ! convert from real value to 16 bits int values
+  where (field < 65530.0)
+    greymap = int(field)
+  end where
+
+  call spit_as_pgm_16(greymap, trim(fname))
+
+  ! make valgrind happy
   deallocate(field)
+  deallocate(greymap)
 
 end subroutine
 
-                !------------------------------------------
+!-----------------------------------------------------------------------
+!-
+!   Compute the gravity field in a pre-allocated array relative
+!   to the massbody 'moon'. Nobody know where the magic number
+!   come from, sorry.
+!-
+subroutine compute_a_field(field, moon)
+  real, dimension(:,:), intent(out)  :: field
+  type(massbody), intent(in)         :: moon
+
+  integer                            :: ix, iy
+  real                               :: fx, fy
+  real                               :: grav
+
+  ! print *, "pic size  ", ubound(field, 1), "W", ubound(field, 2), "H"
+  ! print *, "mass body ", moon
+
+  do ix=1, ubound(field, 1)
+    fx = real(ix)
+    do iy=1, ubound(field, 2)
+      fy = real(iy)
+      grav = compute_gravity(fx, fy, moon)
+      field(ix,iy) = grav
+    enddo
+  enddo
+
+end subroutine
+!-----------------------------------------------------------------------
+!-----------------------------------------------------------------------
 
 end program

GravityField/realfield.f90

@@ -6,7 +6,8 @@ module realfield
   implicit none
 
 !-----------------------------------------------------------------------
-
+!      definition of structures
+!
 type massbody
   real                  :: posx, posy
   real                  :: mass          = 1.0
@@ -17,23 +18,20 @@ end type
 contains
 !-----------------------------------------------------------------------
 
-function compute_gravity(ix, iy, body)
+function compute_gravity(fx, fy, body)
-
+  real, intent(in)              :: fx, fy
-  integer, intent(in)           :: ix, iy
   type(massbody), intent(in)    :: body
   real                          :: compute_gravity
   real                          :: rx, ry, dist
 
-  rx = real(ix) - body%posx
+  rx = fx - body%posx
-  ry = real(iy) - body%posy
+  ry = fy - body%posy
-
   dist = sqrt( (rx*rx) + (ry*ry) )
-  if (dist .LT. 0.15) then
+  if (dist .LT. 4.50) then
     write (0, *) "dist too small ", dist
     compute_gravity = 0e0
   endif
-
+  compute_gravity = body%mass / (dist ** 2)
-  compute_gravity = body%mass * (dist ** 2)
 
 end function
 

GravityField/runme.sh

@@ -4,4 +4,7 @@ set -e				# stop on error
 
 make essai
 
-time ./essai
+./essai
+
+convert -delay 10 WS/*.pgm foo.gif
+