Add vector operations to utilities

[grits] / src / grits-util.c

diff --git a/src/grits-util.c b/src/grits-util.c
index d42cee59d1a33c9c2b06e3950a49258ad0548b8c..26135964e0c5d6f6080e22fb1273b280f80d974d 100644 (file)
--- a/src/grits-util.c
+++ b/src/grits-util.c
@@ -16,7 +16,7 @@
  */
 
 /**
- * SECTION:gis-util
+ * SECTION:grits-util
  * @short_description: Geographic utilities
  *
  * Miscellaneous utility functions, these deal mostly with coordinate
@@ -71,13 +71,13 @@
 #include <glib.h>
 #include <math.h>
 
-#include "gis-util.h"
+#include "grits-util.h"
 
 /************
- * GisPoint *
+ * GritsPoint *
  ************/
 /**
- * gis_point_set_lle:
+ * grits_point_set_lle:
  * @point: the point to modify
  * @lat:   the new latitude
  * @lon:   the new longitude
@@ -85,7 +85,7 @@
  *
  * Set the latitude, longitude, and elevation for a point.
  */
-void gis_point_set_lle(GisPoint *point, gdouble lat, gdouble lon, gdouble elev)
+void grits_point_set_lle(GritsPoint *point, gdouble lat, gdouble lon, gdouble elev)
 {
        point->lat  = lat;
        point->lon  = lon;
@@ -93,11 +93,11 @@ void gis_point_set_lle(GisPoint *point, gdouble lat, gdouble lon, gdouble elev)
 }
 
 
-/*************
- * GisBounds *
- *************/
+/***************
+ * GritsBounds *
+ ***************/
 /**
- * gis_bounds_set_bounds:
+ * grits_bounds_set_bounds:
  * @n: the north edge
  * @s: the south edge
  * @e: the east edge
@@ -105,7 +105,7 @@ void gis_point_set_lle(GisPoint *point, gdouble lat, gdouble lon, gdouble elev)
  *
  * Set the north, south, east, and west edges of the bounding box
  */
-void gis_bounds_set_bounds(GisBounds *bounds,
+void grits_bounds_set_bounds(GritsBounds *bounds,
                gdouble n, gdouble s, gdouble e, gdouble w)
 {
        bounds->n = n;
@@ -235,3 +235,71 @@ gdouble lon_avg(gdouble a, gdouble b)
        }
        return avg;
 }
+
+/**
+ * crossd3:
+ * @a:   the left   point
+ * @b:   the center point
+ * @c:   the right  point
+ * @out: the cross product
+ *
+ * Calculate the cross product of three points
+ */
+void crossd3(gdouble *a, gdouble *b, gdouble *c, gdouble *out)
+{
+       double ba[3], bc[3];
+
+       ba[0] = a[0] - b[0];
+       ba[1] = a[1] - b[1];
+       ba[2] = a[2] - b[2];
+
+       bc[0] = c[0] - b[0];
+       bc[1] = c[1] - b[1];
+       bc[2] = c[2] - b[2];
+
+       crossd(ba, bc, out);
+}
+
+/**
+ * crossd:
+ * @a: the first vector
+ * @b: the second vector
+ * @c: the cross product
+ *
+ * Calculate the cross product of two vectors
+ */
+void crossd(gdouble *a, gdouble *b, gdouble *out)
+{
+       out[0] = a[1] * b[2] - a[2] * b[1];
+       out[1] = a[2] * b[0] - a[0] * b[2];
+       out[2] = a[0] * b[1] - a[1] * b[0];
+}
+
+/**
+ * lengthd:
+ * @a: the vector
+ *
+ * Calculate the length (magnitude) of a vector.
+ *
+ * Returns: the length
+ */
+gdouble lengthd(gdouble *a)
+{
+       return sqrt(a[0] * a[0] +
+                   a[1] * a[1] +
+                   a[2] * a[2]);
+}
+
+/**
+ * normd:
+ * @a: the first longitude
+ *
+ * Normalize a vector to a mangitude of 1
+ */
+void normd(gdouble *a)
+{
+       gdouble total = lengthd(a);
+       a[0] = a[0] / total;
+       a[1] = a[1] / total;
+       a[2] = a[2] / total;
+}