Fortraneries/Fraktalism/henon.f90

68 lines
1.5 KiB
Fortran

program henon
implicit none
integer :: passe
double precision :: vx, vy
integer :: w, h
integer :: foo, bar
double precision :: px, py
w = 2000 ; h=1600
write(0, *) "###### Mapping of Henon "
do foo=1, 16
px = dble(foo) / 16.0
do bar=1,16
py = dble(bar) / 16.0
call compute_pixel_henon(px, py, 1700, &
passe, dble(0.5), vx, vy)
write(0, fmt=*) "passe ", passe, vx, vy
enddo
end do
!-----------------------------------------------------
contains
!-----------------------------------------------------
!-----------------------------------------------------
subroutine compute_pixel_henon(a, b, maxpasse, passe, limit, rx, ry)
implicit none
double precision, intent(in) :: a, b, limit
integer, intent(in) :: maxpasse
integer, intent(out) :: passe
double precision, intent(out) :: rx, ry
double precision :: x, y, x2, y2
write(0, fmt="('compute pixel:', (2F8.3, I6, F8.3))") &
a, b, maxpasse, limit
x = 0.0
y = 0.0
do passe=1, maxpasse
x2 = 1d0 + y - (a * x * x)
y2 = b * x
x = x2
y = y2
write(0, fmt="(i4, 2F8.3)") passe, x, y
if (x .lt. -limit) exit
if (x .gt. limit) exit
if (y .lt. -limit) exit
if (y .gt. limit) exit
enddo
rx = x
ry = y
end subroutine
!-----------------------------------------------------
end program