Changeset 671 for inundation/ga/storm_surge/pyvolution/util_ext.c

Timestamp:

Dec 5, 2004, 8:21:43 PM (20 years ago)

Author:

ole

Message:

Implemented point_on_line in C.

File:

• inundation/ga/storm_surge/pyvolution/util_ext.c (modified) (2 diffs)

inundation/ga/storm_surge/pyvolution/util_ext.c

@@ -18 +18 @@
 
 
-// Gateway to Python
+
+int _point_on_line(double x, double y, 
+                   double x0, double y0, 
+                   double x1, double y1) {
+  /*Determine whether a point is on a line segment 
+   
+    Input: x, y, x0, x0, x1, y1: where
+        point is given by x, y
+        line is given by (x0, y0) and (x1, y1)
+        
+  */
+    
+  double a0, a1, a_normal0, a_normal1, b0, b1, len_a, len_b;
+  
+  a0 = x - x0;
+  a1 = y - y0; 
+  
+  a_normal0 = a1;
+  a_normal1 = -a0;
+                        
+  b0 = x1 - x0;
+  b1 = y1 - y0;
+    
+  if ( a_normal0*b0 + a_normal1*b1 == 0 ) {   
+    //Point is somewhere on the infinite extension of the line
+
+    len_a = sqrt(a0*a0 + a1*a1);               
+    len_b = sqrt(b0*b0 + b1*b1);
+                                        
+    if (a0*b0 + a1*b1 >= 0 && len_a <= len_b) {
+      return 1;
+    } else {
+      return 0;
+    }
+  } else {
+    return 0;
+  }
+}
+
+
+
+// Gateways to Python
+PyObject *point_on_line(PyObject *self, PyObject *args) {
+  //
+  // point_on_line(x, y, x0, y0, x1, y1)
+  //
+  
+  double x, y, x0, y0, x1, y1;
+  int res;
+  PyObject *result;
+  
+  // Convert Python arguments to C  
+  if (!PyArg_ParseTuple(args, "dddddd", &x, &y, &x0, &y0, &x1, &y1))  
+    return NULL;
+
+  
+  // Call underlying routine
+  res = _point_on_line(x, y, x0, y0, x1, y1);
+
+  // Return values a and b
+  result = Py_BuildValue("i", res);
+  return result;
+}
+
+
 PyObject *gradient(PyObject *self, PyObject *args) {
   //
@@ -52 +116 @@
   //{"rotate", (PyCFunction)rotate, METH_VARARGS | METH_KEYWORDS, "Print out"},  
   {"gradient", gradient, METH_VARARGS, "Print out"},    
+  {"point_on_line", point_on_line, METH_VARARGS, "Print out"},      
   {NULL, NULL, 0, NULL}   /* sentinel */
 };