check for tiny values in dir[] vector in calcposobjs(), prevents FP underflows later
diff --git a/progs/demos/fire.c b/progs/demos/fire.c
index e895b0e..e4492cb 100644
--- a/progs/demos/fire.c
+++ b/progs/demos/fire.c
@@ -257,6 +257,13 @@
    dir[2] = cos(alpha * M_PI / 180.0) * sin(beta * M_PI / 180.0);
    dir[1] = cos(beta * M_PI / 180.0);
 
+   if (dir[0] < 1.0e-5 && dir[0] > -1.0e-5)
+      dir[0] = 0;
+   if (dir[1] < 1.0e-5 && dir[1] > -1.0e-5)
+      dir[1] = 0;
+   if (dir[2] < 1.0e-5 && dir[2] > -1.0e-5)
+      dir[2] = 0;
+
    obs[0] += v * dir[0];
    obs[1] += v * dir[1];
    obs[2] += v * dir[2];