From df4f574951b0c4db1854e7d08104b4a1eea54bbb Mon Sep 17 00:00:00 2001 From: James Turner Date: Wed, 7 Aug 2013 16:30:20 +0100 Subject: [PATCH] Fix horizon sunrise/sunset effect position. Fix sun position in default renderer. (Committing fix provided after discussion on IRC + forum, no bug ID) --- src/Time/light.cxx | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/src/Time/light.cxx b/src/Time/light.cxx index 5ccbcff27..ceb17d239 100644 --- a/src/Time/light.cxx +++ b/src/Time/light.cxx @@ -361,7 +361,10 @@ void FGLight::update_adj_fog_color () { sif = 1e-4; // determine horizontal angle between current view direction and sun - double hor_rotation = -_sun_rotation - SGD_PI_2 - heading + heading_offset; + // since _sun_rotation is relative to South, and heading is in the local frame + // we need to account for the 180 degrees offset and differing signs + // hence the negation and SGD_PI adjustment. + double hor_rotation = -_sun_rotation - SGD_PI - heading + heading_offset; if (hor_rotation < 0 ) hor_rotation = fmod(hor_rotation, SGD_2PI) + SGD_2PI; else @@ -430,8 +433,14 @@ void FGLight::updateSunPos() // Get direction to the sun in the local frame. SGVec3d local_sun_vec = hlOr.transform(nsun); - // Angle from south. - _sun_rotation = 2.0 * atan2(local_sun_vec.x(), -local_sun_vec.y()); + // Angle from South. + // atan2(y,x) returns the angle between the positive X-axis + // and the vector with the origin at 0, going through (x,y) + // Since the local frame coordinates have x-positive pointing Nord and + // y-positive pointing East we need to negate local_sun_vec.x() + // _sun_rotation is positive counterclockwise from South (sun in the East) + // and negative clockwise from South (sun in the West) + _sun_rotation = atan2(local_sun_vec.y(), -local_sun_vec.x()); // cout << " Sky needs to rotate = " << _sun_rotation << " rads = " // << _sun_rotation * SGD_RADIANS_TO_DEGREES << " degrees." << endl;