
3 SURFACE
	SURFace plots 3 dimensional data using a wire frame with
	hidden line removal.
	The simplist SURFACE file would look like this.
		BEGIN SURFACE
			DATA myfile.z 5 5
		END SURFACE

	More help is available on the following topics:

	SIZE	CUBE	XAXIS	YAXIS	ZAXIS
	XTITLE	YTITLE	ZTITLE  DATA	ROTATE
	VIEW	TOP	UNDERNEATH	SKIRT
	XLINES	YLINES 	POINTS	MARKER	DROPLINES
	RISELINES	HARRAY	BACK	BASE
	RIGHT 	TITLE   ZCLIP	NOBIGFILE

4 SIZE
	Specifies the size in cm to draw the surface.  The 3d cube
	will fit inside this box.  The default is 18cm x 18cm

	e.g.	SIZE 10 10

4 HARRAY
	The hidden line removal is accomplished with the help of
	an array of heights which record the current horizon,  the
	quality of the output is proportional to the width of this
	array.  (also the speed of output)

	To get good quality you may want to increase this from
	the default of about 900 to 2 or 3 thousand.

	e.g.	HARRAY 2000

4 CUBE
	CUBE  OFF  XLEN v YLEN v ZLEN v  NOFRONT LSTYLE l COLOR c

	OFF	Stops GLE from drawing the cube.
	XLEN	The length of the cubes x dimension in cm.
	NOFRONT	Removes the front three lines of the cube.
	LSTYLE	Sets the line style to use drawing the cube.
	COLOR 	Sets the color of lines to use drawing the cube.

4 XAXIS
	XAXIS MIN v  MAX v  STEP v  COLOR c LSTYLE l HEI v OFF

	MIN,MAX	Set the range used for labelling the axis.
	STEP	The distance between labels on the axis.
	COLOR	The color of the axis ticks and labels.
	LSTYLE	The line style used for drawing the ticks.
	TICKLEN	The length of the ticks.
	HEI	The height of text used for labelling.
	OFF	Stops GLE from drawing the axis.

4 YAXIS
	YAXIS MIN v  MAX v  STEP v  COLOR c LSTYLE l HEI v OFF

	MIN,MAX	Set the range used for labelling the axis.
	STEP	The distance between labels on the axis.
	COLOR	The color of the axis ticks and labels.
	LSTYLE	The line style used for drawing the ticks.
	TICKLEN	The length of the ticks.
	HEI	The height of text used for labelling.
	OFF	Stops GLE from drawing the axis.

4 ZCLIP
	ZCLIP  MIN v1  MAX v2
	
	ZCLIP goes through the Z array and sets any Z value smaller
	than MIN to V1 and sets any value greater than MAX to v2.

4 ZAXIS
	ZAXIS MIN v  MAX v  STEP v  COLOR c LSTYLE l HEI v OFF

	MIN,MAX	Set the range used for labelling the axis.
		(Also sets the range of Z values)
	STEP	The distance between labels on the axis.
	COLOR	The color of the axis ticks and labels.
	LSTYLE	The line style used for drawing the ticks.
	TICKLEN	The length of the ticks.
	HEI	The height of text used for labelling.
	OFF	Stops GLE from drawing the axis.

4 XTITLE
	XTITLE "X title"  DIST v COLOR c HEI v

	DIST	Moves the title further away from the axis.
	COLOR	Sets the color of the title.
	HEI	Sets the hei in cm of the text used for the title.

4 YTITLE
	YTITLE "Y title"  DIST v COLOR c HEI v

	DIST	Moves the title further away from the axis.
	COLOR	Sets the color of the title.
	HEI	Sets the hei in cm of the text used for the title.

4 ZTITLE
	ZTITLE "Z title"  DIST v COLOR c HEI v

	DIST	Moves the title further away from the axis.
	COLOR	Sets the color of the title.
	HEI	Sets the hei in cm of the text used for the title.

4 TITLE
	TITLE "Main title"  DIST v COLOR c HEI v

	DIST	Moves the title further away from the axis.
	COLOR	Sets the color of the title.
	HEI	Sets the hei in cm of the text used for the title.

4 DATA
	DATA myfile.z  XSAMPLE n1 YSAMPLE n2 SAMPLE n3  NX n1 NY n2

	Loads a file of Z values in.  The NX and NY dimensions
	are optional, normally the dimensions of the data will
	be defined on the first line of the data file.
	e.g.

	! NX 10  NY 20    XMIN 1 XMAX 10 YMIN 1 YMAX 20
	1 2 42 4 5 2 31 4 3 2 4
	1 2 42 4 5 2 31 4 3 2 4 etc...

	Data files can be created using LETZ or FITZ.
	LETZ will create a data file from an x,y function.
	FITZ will create a data file from a list of x,y,z data points.

	XSAMPLE Tells surface to only read every n'th data point from
                the data file.  This speeds things up while you are
                messing around.		
	YSAMPLE Tells surface to only read every n'th line from the 
                data file.
	SAMPLE	Sets both XSAMPLE and YSAMPLE

	(see also POINTS)

4 ROTATE
	ROTATE 10 20 30

	Imagine the unit cube is sitting on the front of your
	terminal screen, x along the bottom, y up the left hand
	side, and z coming towards you.

	The first number (10) rotates the cube along the xaxis, ie
	hold the right hand side of the cube and rotate your hand
	clockwise 10 degrees.

	The second number (20) rotates the cube along the yaxis, ie
	hold the top of the cube and rotate it 20 degrees clockwise.

	The third number is currently ignored.

	The default setting is 60 50 0.

4 VIEW
	VIEW x y p

	Sets the perspective, this is where the cube gets smaller
	as the lines dissappear towards infinity.

	x and y are the position of infinity on your screen.
	p is the degree of perspective, 0 = no perspective
	and with 1 the back edge of the box will be touching
	infinitiy.  Good values are between 0 and 0.6

4 TOP
	TOP OFF   LSTYLE n  COLOR c

	Sets the features of the top of the surface.

	By default the top is on.

	(see also UNDERNEATH, XLINES, YLINES)

4 UNDERNEATH
	UNDERNEATH OFF   LSTYLE n  COLOR c

	Sets the features of the under side of the surface.

	By default the underneath is off.

	(see also TOP, XLINES, YLINES)

4 SKIRT
	SKIRT ON

	Draws a skirt from the edge of the surface to ZMIN.

4 XLINES
	XLINES OFF

	Stops SURF from drawing lines of constant X.

4 YLINES
	YLINES OFF

	Stops SURF from drawing lines of constant Y.

4 POINTS
	POINTS myfile.dat

	Reads in a data file which must have 3 columns (x,y,z)

	This is then used for plotting markers and
	rise and drop lines.

4 MARKER
	MARKER circle HEI v COLOR c

	Draws markers at the co-ordinates read from the POINTS file.

4 DROPLINES
	DROPLINES COLOR c LSTYLE n

	Draws lines from the co-ordinates read from the POINTS file
	down to zmin.

4 RISELINES
	RISELINES COLOR c LSTYLE n

	Draws lines from the co-ordinates read from the POINTS file
	up to zmax.

4 BACK
	BACK ZSTEP v YSTEP v LSTYLE COLOR c NOHIDDEN

	Draws a grid on the back face of the cube.

	By default hidden lines are removed but NOHIDDEN will
	stop this from happenning.

4 BASE
	BASE XSTEP v YSTEP v LSTYLE COLOR c NOHIDDEN

	Draws a grid on the base of the cube.

	By default hidden lines are removed but NOHIDDEN will
	stop this from happenning.

4 RIGHT
	BACK ZSTEP v XSTEP v LSTYLE COLOR c NOHIDDEN

	Draws a grid on the right face of the cube.

	By default hidden lines are removed but NOHIDDEN will
	stop this from happenning.

4 NOBIGFILE
	The flag  NOBIGFILE  prevents Surface from writing
	bigfiles to the disk. This flag speeds up surface
	dramatically on systems without effective cacheing
	of harddisk writes, such as OS/2. For the final run,
	place an exclamation mark in front of 'NOBIGFILE'.
	        
