add Function Field and Intersect examples

benchmarks/2d/function_field.geo

+
+lc = 1;
+Point(1) = {0, 0, 0, lc};
+Point(2) = {1, 0,  0, lc} ;
+Point(3) = {1, 1, 0, lc} ;
+Point(4) = {0, 1, 0, lc} ;
+Line(1) = {1,2} ;
+Line(2) = {3,2} ;
+Line(3) = {3,4} ;
+Line(4) = {4,1} ;
+Line Loop(5) = {4,1,-2,3} ;
+Plane Surface(6) = {5} ;
+
+Function Field(1) = "Cos(2*3.14*x)/5 + 0.21";
+Characteristic Length Field{1};

benchmarks/2d/intersect.geo

+
+N = 10;
+
+lc1 = 0.1;
+lc2 = 0.5;
+
+For i In {1:N}
+  angle = i * 2 * Pi / N;
+  Point(2 * i) = { 2 * Cos(angle), 1 + Sin(angle), -5, lc1};
+  Point(2 * i + 1) = { 2 * Cos(angle), 1 + Sin(angle), 5, lc1};
+  Line(i) = {2 * i, 2 * i + 1};
+EndFor
+
+Point(1000) = {-5, -5, 3, lc2};
+Point(1001) = {-1.7,-5.3,3, lc2};
+Point(1002) = {1.6,-5.1,3, lc2};
+Point(1003) = {5.1,-3.7,2, lc2};
+Point(1004) = {-4.7,-1.5,-1, lc2};
+Point(1005) = {-5.3,1,-2, lc2};
+Point(1006) = {-4.4,4.2,1, lc2};
+Point(1007) = {-1,3.5,3, lc2};
+Point(1008) = {2.6,4.2,3, lc2};
+Point(1009) = {5.5,3.2,1, lc2};
+Point(1010) = {5.4, 1.1,-2, lc2};
+Point(1011) = {5.8,-1.4,-1, lc2};
+
+Spline(11) = {1003,1011,1010,1009};
+Spline(12) = {1009,1008,1007,1006};
+Spline(13) = {1006,1005,1004,1000};
+Spline(14) = {1000,1001,1002,1003};
+Line Loop(15) = {11,12,13,14};
+Ruled Surface(16) = {15};
+
+pp[] = Intersect Line {1:N} Surface {16};
+
+Spline(1000) = {pp[], pp[0]};
+
+Delete { Surface{16}; }
+Hide { Line{1:N}; Point{1:2*N}; }
+
+Line Loop(16) = {1000};
+Ruled Surface(16) = {15, 16};