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64 CHAPTER 8. SURFACE AND CONTOUR PLOTSbegin surfacesize 7 7data "jack.z"cube zlen 13top color orangeunderneath color redend surface3002502001501005000 5 10 15 20 25 302 4 6 8 10 12 14 16 18 20data 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 ofthe 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 201 2 42 4 5 2 31 4 3 2 41 2 42 4 5 2 31 4 3 2 4 etc...y1,x1, y1,x2 ... y1,xny2,x1, y2,x2 ... y2,xn...yn,x1, yn,x2 ... yn,xnData 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.xsampleysamplesampleTells surface to only read every n’th data point fromthe data file. This speeds things up while you aremessing around.Tells surface to only read every n’th line from thedata file.Sets both xsample and ysample(see also POINTS)2begin surfacesize 5 5xtitle "X-axis"ytitle "Y-axis"data "surf1.z"end surface1.81.61.41.211 2 3 4 5X-axis2 3 4Y-axisharray nThe hidden line removal is accomplished with the help of an array of heights which record thecurrent horizon, the quality of the output is proportional to the width of this array. (also the speedof 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 2000xlines offStops SURF from drawing lines of constant X.