Data commit

Task/Draw-a-sphere/Zkl/draw-a-sphere-1.zkl

@@ -0,0 +1,15 @@
+img:=PPM(640,480);
+R:=100; R2:=R*R;           //radius, in pixels; radius squared
+X0:=640/2; Y0:=480/2;      //coordinates of center of screen
+foreach Y in ([-R..R]){    //for all the coordinates near the circle
+   foreach X in ([-R..R]){ // which is under the sphere
+      D2:=X*X + Y*Y;
+      C:=0;                //default color is black
+      if(D2<=R2){          //coordinate is inside circle under sphere
+	 Z:=(R2-D2).toFloat().sqrt();//height of point on surface of sphere above X,Y
+	 C=0x82+Z-(X+Y)/2; //color is proportional; offset X and Y, and
+      }                    // shift color to upper limit of its range
+      img[X+X0,Y+Y0]=C.shiftLeft(8)+C; //green + blue = cyan
+   }
+}
+img.write(File("foo.ppm","wb"));

Task/Draw-a-sphere/Zkl/draw-a-sphere-2.zkl

@@ -0,0 +1 @@
+img[X+X0,Y+Y0]=C*140+C;

Task/Draw-a-sphere/Zkl/draw-a-sphere-3.zkl

@@ -0,0 +1,23 @@
+#<<<
+cmd:=0'|
+set term wxt
+set parametric
+set urange [0:pi]
+set vrange [0:2*pi]
+set xyplane 0
+set view equal xyz
+set pm3d hidden3d 100 depthorder
+set style line 100 lt 7 lw 0.1
+set palette defined (0 "dark-blue", 1 "light-blue")
+unset key
+set samples 24
+set isosamples 36
+set title 'sphere (pm3d)' font "Times,20"
+R = 3
+splot R*sin(u)*cos(v), R*sin(u)*sin(v), R*cos(u) w pm3d
+|;
+#<<<
+
+gnuplot:=System.popen("gnuplot","w");
+gnuplot.write(cmd); gnuplot.flush();
+ask("Hit return to finish"); gnuplot.close();