- double xoff = cos( course ) * dist / (2 * scale);
- double yoff = sin( course ) * dist / (2 * scale);
+ // if start and dest are too close together,
+ // calc_gc_course_dist() can return a course of "nan". If
+ // this happens, lets just use the last known good course.
+ // This is a hack, and it would probably be better to make
+ // calc_gc_course_dist() more robust.
+ if ( isnan(course) ) {
+ course = last_course;
+ } else {
+ last_course = course;
+ }
+
+ // calculate cloud movement due to external forces
+ double ax = 0.0, ay = 0.0, bx = 0.0, by = 0.0;
+
+ if (dist > 0.0) {
+ ax = cos(course) * dist;
+ ay = sin(course) * dist;
+ }
+
+ if (sp_dist > 0) {
+ bx = cos(-direction * SGD_DEGREES_TO_RADIANS) * sp_dist;
+ by = sin(-direction * SGD_DEGREES_TO_RADIANS) * sp_dist;
+ }
+
+
+ double xoff = (ax + bx) / (2 * scale);
+ double yoff = (ay + by) / (2 * scale);