XFOIL机翼性能计算软件

/***********************************************************************

Module: Doc

Copyright (C) 1996 Harold Youngren, Mark Drela

This library is free software; you can redistribute it and/or

modify it under the terms of the GNU Library General Public

License as published by the Free Software Foundation; either

License along with this library; if not, write to the Free

Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

Report problems to: guppy@maine.com

or drela@mit.edu

***********************************************************************/

Xplot11 Graphics Package "Documentation"

C Version 4.46 11/28/01

(submitted in partial fullfillment of the

necessity of documenting this package)

History

equipment at MIT's Gas Turbine Lab. At this point the package has

been hacked and extended to the point where no trace of the original

source code remains (that is definitely for the best...). Note that

this package is not PLOT10 compatible, it is closer to a Versatec

graphics library.

The basic philosophy of page-by-page plotting for both the screen

window and hardcopy output has been retained. At the device level,

the major changes have been the use of X-Windows for screen display output,

and PostScript for hardcopy output, neither of which existed when

the original Versatec software was developed. Also, both B&W and Color

which require more flexibility and power than simple X-versus-Y line plot

packages, but don't require the complexity of full event-driven screen

graphics interaction. It has the following key features:

+ Direct move-to, draw-to

+ Polyline plot, polygon fill

+ Terminal-type WYSIWYG vector font

+ LaTex-like Greek and math symbol vector font

+ Automatic offset/scaling

+ Automatic zooming

+ Automatic clipping against arbitrary "box"

+ Automatic plot primitive storage in display list for X-window replot

and/or PostScript hardcopy.

+ Color X-graphics and color PostScript support (or black & white)

The last item represents the only capability for "interactive" graphics.

- Bitmap constructs

- Continuous X-event recognition

- Read/Write Colormaps

- Multiple X windows

- full 3D support (you really ought to be using OpenGL at that point)

Implementation

--------------

Xplot11 is implemented at three basic levels of routines, but only

the first, user-level group is called in applications.

+ user level routines - these are in the files:

plt_font.f

+ an intermediate level that scales between user and plot, clips and zooms,

and handles replotting - these are in the file:

set_subs.f

+ a hardware support level that interfaces to the postscript and X-windows

ps_subs.f

gw_subs.f

Xwin.c

One major purpose of the intermediate level is to permit the automatic

the support-level routines again, but now with PostScript output enabled.

------------

As mentioned above the plot library only supports two devices, the X-window

display and hardcopy in the form of output files in postscript. The plot

device is selected for each plot in the PLOPEN statement which has the

form:

CALL PLOPEN(relsize,lpsunit,idev)

where idev selects the plotting destination as follows:

5 x Color

Note that odd idev's include plotting to the X-window, even values select

postscript only and can be used with REPLOT to get a hardcopy of the

current plot.

The lpsunit input specifies the logical unit to use for the postscript output.

If lpsunit=0 Xplot11 writes to unit 80 and to a file called "plot.ps". If

"plotunitNNN.ps" where NNN=lpsunit. If an open file is found on unit #lpsunit

Xplot11 will assume the unit is under external program control and will only

write postscript data to it, no OPENs, CLOSEs or REWINDs will be done. If

lpsunit<0 is specified separate "plotNNN.ps" files are generated for each

plot, written to logical unit 80. Separate plot files are numbered starting

with NNN=000 (i.e. "plot000.ps") and file names are incremented for each plot.

The first parameter, relsize, gives the relative window size and orientation

0.6 of the size of the root X-window. If relsize+>0 the page is in Landscape

----------------

A call to REPLOT(idev) uses the same plotting destinations used in the

PLOPEN call discussed above. Normally REPLOT is used for either zooming

a previous plot (with REPLOT(1)) or to make a hardcopy of the current plot

This automatic logging and replot capability means that the user program

does not need to be structured to regenerate the plot on demand. This is

well suited to the kind of program structure used for simple Fortran

analysis codes (more casual than event-driven programming).

pltlib.inc, normally 100,000 or more primitives are stored) then the array

user closes plotting.

----------------------------

The Xplot11 user interface works with two plotting coordinate systems:

* User units x,y (arbitrary units)

* Absolute units X,Y (inches for PostScript, pseudo_inches for X-graphics)

1 pseudo_inch on the X-window will show up as 1 inch on PostScript.

For brevity, a pseudo_inch will be referred to simply as "Inch" henceforth.

you can make the following source code changes...

In subroutine ps_init (in ps_subs.f):

ccc if(P_SCALE.EQ.0.) P_SCALE = 72.

if(P_SCALE.EQ.0.) P_SCALE = 72. / 2.54

ccc DATA iwdefsize, w1size, w2size / 1000, 11.00, 8.50 /

DATA iwdefsize, w1size, w2size / 1000, 27.94, 21.59 /

...and then translate "inch" to "centimeter" in this file.

to match your strange and unnatural paper dimensions in cm.

The absolute (X,Y) axes always span the X-window and PostScript page as

shown below. The user (x,y) axes are relocatable within the screen or page,

and are provided mainly for programming convenience:

| |

| |

| |

| | |

| | |

| +------------- |

0 +-------------------------------

0 X X_PAGE

The transformation (x,y) -> (X,Y) is defined as

X = X_SCALE*x + X_ORG

Y = Y_SCALE*y + Y_ORG

with the start-up values of the offset/scaling transformation parameters being

X_SCALE = 1.

Y_SCALE = 1.

CALL NEWORIGIN(X_ORG,Y_ORG)

Alternatively one could use the "move-to & re-origin" PLOTABS call.

CALL PLOTABS(X_ORG,Y_ORG,-3)

CALL NEWFACTORS(X_SCALE,Y_SCALE)

changed again or a new plot page is opened with CALL PLOPEN.

Alternatively (and confusingly), one can also change the absolute

transformation offsets X_ORG,Y_ORG via the current user coordinates by

CALL PLOT(x_org,y_org,-3)

transformation:

conceptually much simpler.

Another alternative way, rather than independently setting origins

and scale factors, is to set the complete user-absolute

CALL NEWUSERTRANS(X_ORG,Y_ORG,X_SCALE,Y_SCALE)

For convenience, transformation function routines for direct evaluation

of x(X), y(Y), X(x), Y(y) are provided:

FUNCTION xusr2ABS(x)

Note that the user-to-absolute tranformation can be queried with

CALL GETUSERTRANS(X_ORG,Y_ORG,X_SCALE,Y_SCALE)

or

CALL GETORIGIN(X_ORG,Y_ORG) and