% @(#)createart_.hlq	17.1.1.1 (ESO-IPG) 01/25/02 17:14:49 
%++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
%.COPYRIGHT  (c)  1990 European Southern Observatory
%.IDENT      createart_.hlq
%.AUTHOR     KB, IPG/ESO
%.KEYWORDS   MIDAS, help files, CREATE/ART_IMAGE
%.PURPOSE    On-line help file for the command: CREATE/ART_IMAGE
%.VERSION    1.0  07-NOV-1990 : Creation, KB
%----------------------------------------------------------------
\se
SECTION./ART_
\es\co
CREATE/ART_IMAGE                                          26-FEB-1992  PB
\oc\su
CREATE/ART_IMAGE frame frame dims [starts,steps] [func_type] [coefs]
CREATE/ART_IMAGE frame = ref_frame [func_type] [coefs]
	create artificial image
\us\pu
Purpose:      
     Create a new artifical image frame.
\up\sub
Subject:      
     Artificial frames, models, fractals.
\bus\sy
Syntax:       
     CREATE/ART_IMAGE frame [dims] [starts,steps] [func_type] [coefs]\\
              or\\
     CREATE/ART_IMAGE frame = ref_frame [func_type] [coefs]
\ys\pa
     frame = name of new frame
\ap\pa
     ref_frame = reference frame, i.e. take all descriptors from that frame
\ap\pa
     dims =       NAXIS,NPIX(1),...,NPIX(NAXIS); default:  2,512,512
\ap\pa
     starts,steps = START(1),...,START(NAXIS),STEP(1),...,STEP(NAXIS)\\
                  default: = -1.3 for START(i), = 0.005 for STEP(i)\\
                  Start and step may have to be adapted depending on the
                  chosen function and coefficients.
\ap\pa
      func_type = type of function used to define the content of the created 
                  image:\\
                  MANDEL for creation of Mandelbrot set   \\
                  JULIA for creation of Julia set\\
                  LORENZ for creation of Lorenz attractors \\
                  ELFLY for simulation of a chaotic system (electronic fly)\\
                  COLWHEEL for creation of a colour wheel\\
                  Default: LORENZ
\ap\pa
      coefs = coefficients for the function which is used to create the
                  image, number and meaning depends on the parameter 
                  func_type:\\
                  MANDEL    zx,zy,uplimit     default: .31,.04,100\\
                  JULIA     zx,zy,uplimit     default: .31,.04,100\\
                  LORENZ    x0,y0,z0,h,a,b,n_iter   \\
                            default: 1,1,1,.01,28,0.1,10000\\
                  ELFLY     a,b,c,d,e,f,n_iter   \\
                            default: 2.24,.43,-.65,-2.43,1.,300000
\ap\no
Note:         
              For MANDEL and JULIA, the coefficients represent zx,zy,uplimit 
              where zx and zy are the real and imaginary part of a complex 
              number zz, which serves as the initial value for z in the 
              formula:\\
              z <- z*z + c \\
              the real and imaginary parts of c are the x,y coords
\\
              If after 256 iterations z <= uplimit, the pixel at (x,y) is
              set to 0.0, else pixel <- iteration_no .
\\
              For ELFLY, the coefficients represent a,b,c,d,e,f,no_iter where
              a,b,c,d,e,f are control parameters and no_iter the number of
              loops for evaluation of the formulaes:\\
              xx = sin(a*y) - z*cos(b*x)\\ 
              yy = z*sin(c*x) - cos(d*y)\\
              zz = e*sin(x)\\
              x = xx, y = yy, z = zz.\\
              the pixel value at resulting x,y coords (z is discarded) is
              increased by 1.0 .
\\
              For LORENZ, the coefficients represent x0,y0,z0,h,a,b,no_iter 
              where x0,y0,z0 are the inital value for a point in space,
              h,a,b are coefficients and no_iter the number of loops for 
              evaluating the formulae:\\
              xx = x + 10.*h*(y-x)\\ 
              yy = y = h*((-x*z)+a*x-y)\\
              zz = z + h*(x*y-b*z)\\
              x = xx, y = yy, z = zz.\\
              the pixel value at resulting x,y coords (z is discarded) is
              set to 1.0 .
\on\exs
Examples:     
\ex
      CREATE/ART mandel ?  -1.6,-1.3,0.05,0.05  MANDEL
\xe\ex
      CREATE/ART julia  P4=JULIA
\xe\ex
      CREATE/ART lorenz ? -25,-25,0.1,0.1 LO .1,.1,.1,.01,28,2.66,4000
\xe\ex
      CREATE/ART elfly ? -2.5,-2.5,0.01,0.01 ELFLY 2.24,.43,-.65,-2.43,1,300000
\xe\sxe