added Ray::randomRay() to generated a ray with origin at (0,0,0) and a random direction

git-svn-id: svn://anubis/fart/trunk@254 7f9b0f55-74a9-4bce-be96-3c2cd072584d

main/fart.cc

@@ -1,15 +1,19 @@
 
-#include <iostream>
 #include <string.h>
 #include <unistd.h>                 /* sysconf() */
-#include <stdlib.h>
+#include <stdlib.h>                 /* rand(), srand() */
+#include <time.h>                   /* time() */
 #include <getopt.h>
 #include <sys/time.h>               /* gettimeofday() */
+
+#include <iostream>
 #include <string>
 #include <map>
+
 #include "Scene.h"
 #include "distrib/distrib.h"
 #include "BMP.h"
+
 using namespace std;
 
 void usage(const char * progname)
@@ -163,6 +167,8 @@ int main(int argc, char * argv[])
         usage(argv[0]);
     }
 
+    srand(time(NULL));
+
     const char * filename = argv[optind];
     client_options.push_back(filename);
     Scene scene(scene_options, filename);

util/Ray.cc

@@ -1,6 +1,9 @@
 
+#include <stdlib.h>                 /* rand() */
+
+#include <iostream>
+
 #include "Ray.h"
-#include <iostream>
 
 Ray::Ray()
 {
@@ -13,6 +16,18 @@ Ray::Ray(const Vector & origin, const Vector & direction)
     m_direction.normalize();
 }
 
+Ray Ray::randomRay()
+{
+    double x, y, z;
+    do
+    {
+        x = 2.0 * rand() / RAND_MAX - 1.0;
+        y = 2.0 * rand() / RAND_MAX - 1.0;
+        z = 2.0 * rand() / RAND_MAX - 1.0;
+    } while (x*x + y*y + z*z <= 1.0);
+    return Ray(Vector(0, 0, 0), Vector(x, y, z));
+}
+
 /*
  * return a vector for the point at distance dist
  * from the ray's origin point, along its direction.

util/Ray.h

@@ -10,6 +10,7 @@ class Ray
     public:
         Ray();
         Ray(const Vector & origin, const Vector & direction);
+        static Ray randomRay();
         const Vector & getOrigin() const { return m_origin; }
         const Vector & getDirection() const { return m_direction; }
         Vector getPositionAt(double dist) const;