[grits] Increase camera angle to 60 degrees

[Andy Spencer <andys src gnome org>]

commit 7138d9be203921e2eaa3168932c463ed790456c0
Author: Andy Spencer <andy753421 gmail com>
Date:   Fri Feb 10 18:26:50 2012 +0000

    Increase camera angle to 60 degrees
    
    Using the 30 degree viewing angle looks reasonable realistic,
    but is difficult to use since it requires much more panning.
    
    Derivation of FOV_DIST for a 1600x1200 monitor
    with a vertical viewing angle of 60 degrees:
    
            ---  +.
             |   | '-.     angle
      height |   |    '-./
      (px)   |   |      /'-.
             |   +------|---+ (o) eye
             |   |      \ .-'
             |   |     .-'
             |   |  .-'
            ---  +-'
    
                 |----------|
                   FOV_DIST (px)
    
      height   = 1200 px
      angle    =   60 deg
      fov_dist = cot(angle/2)*(height/2) = ~1039.23
    
    Derivation of angle for window of a given height:
    
      angle    = atan((height/2)/FOV_DIST)*2

 src/grits-opengl.c |    2 +-
 src/grits-util.h   |    2 +-
 src/grits-viewer.c |    8 ++++----
 3 files changed, 6 insertions(+), 6 deletions(-)
---
diff --git a/src/grits-opengl.c b/src/grits-opengl.c
index 5bf1710..1b2cce9 100644
--- a/src/grits-opengl.c
+++ b/src/grits-opengl.c
@@ -67,7 +67,7 @@ static void _set_visuals(GritsOpenGL *opengl)
 
 	double width  = GTK_WIDGET(opengl)->allocation.width;
 	double height = GTK_WIDGET(opengl)->allocation.height;
-	double ang    = atan(height/FOV_DIST);
+	double ang    = atan((height/2)/FOV_DIST)*2;
 	double atmos  = 100000;
 	double near   = MAX(elev*0.75 - atmos, 50); // View 100km of atmosphere
 	double far    = elev + 2*EARTH_R + atmos;   // on both sides of the earth
diff --git a/src/grits-util.h b/src/grits-util.h
index 8e7a2fd..9a22ab5 100644
--- a/src/grits-util.h
+++ b/src/grits-util.h
@@ -180,7 +180,7 @@ void grits_bounds_set_bounds(GritsBounds *bounds,
  *
  * Used by GritsOpenGL to set up the drawing window
  */
-#define FOV_DIST   2078.46
+#define FOV_DIST   (1039.23)
 
 /**
  * MPPX:
diff --git a/src/grits-viewer.c b/src/grits-viewer.c
index b4b672a..f7d70e9 100644
--- a/src/grits-viewer.c
+++ b/src/grits-viewer.c
@@ -163,11 +163,11 @@ static gboolean on_motion_notify(GritsViewer *viewer, GdkEventMotion *event, gpo
 	gdouble lat, lon, elev, scale, rx, ry, rz;
 	grits_viewer_get_location(GRITS_VIEWER(viewer), &lat, &lon, &elev);
 	grits_viewer_get_rotation(GRITS_VIEWER(viewer), &rx,  &ry,  &rz);
-	scale = (elev/EARTH_R/40) * (sin(deg2rad(ABS(rx)))*4+1);
+	scale = (elev/EARTH_R/14.1) * (sin(deg2rad(ABS(rx)))*4+1);
 	switch (viewer->drag_mode) {
-	case GRITS_DRAG_PAN:  grits_viewer_pan(viewer, -y*scale, x*scale, 0); break;
+	case GRITS_DRAG_PAN:  grits_viewer_pan(viewer, -y*scale*0.782, x*scale, 0); break;
 	case GRITS_DRAG_ZOOM: grits_viewer_zoom(viewer, pow(2, -y/500)); break;
-	case GRITS_DRAG_TILT: grits_viewer_rotate(viewer, y/30, 0, x/20); break;
+	case GRITS_DRAG_TILT: grits_viewer_rotate(viewer, y/10, 0, x/10); break;
 	}
 	viewer->drag_x = event->x;
 	viewer->drag_y = event->y;
@@ -587,7 +587,7 @@ static void grits_viewer_init(GritsViewer *viewer)
 	viewer->time        = time(NULL);
 	viewer->location[0] = 40;
 	viewer->location[1] = -100;
-	viewer->location[2] = 4*EARTH_R;
+	viewer->location[2] = EARTH_R;
 	viewer->rotation[0] = 0;
 	viewer->rotation[1] = 0;
 	viewer->rotation[2] = 0;