constant scale for perspective

diff --git a/src/opengl.c b/src/opengl.c
index 94d1cd18a840151469aef70efb31f02fec8407b7..09b41d5fa1aa8354d3bc41ebb2007542538a8f44 100644 (file)
--- a/src/opengl.c
+++ b/src/opengl.c
@@ -1,4 +1,5 @@
 #include <config.h>
+#include <math.h>
 #include <gtk/gtk.h>
 #include <gtk/gtkgl.h>
 #include <GL/gl.h>
@@ -42,22 +43,24 @@ static gboolean configure_start(GtkWidget *da, GdkEventConfigure *event, gpointe
        if (!gdk_gl_drawable_gl_begin(gldrawable, glcontext))
                g_assert_not_reached();
 
-       glViewport(0, 0, da->allocation.width, da->allocation.height);
+
+       double width  = da->allocation.width;
+       double height = da->allocation.height;
+       double dist   = 500*1000; // 500 km
+       glViewport(0, 0, width, height);
 
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
-       //glRotatef(0, 0, 2, 45);
-       gluPerspective(45.0f, 1, 0.1f, 10000000.0f);
-       //glFrustum(-1, 1, -1, 1, -1, 1);
+       double rad = atan(height/2*1000.0/dist); // 1px = 1000 meters
+       double deg = (rad*180)/M_PI;
+       gluPerspective(deg*2, width/height, 0.1f, 10000000.0f);
 
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
-       double scale = 500*1000; // 500 km
-       //glOrtho(-scale,scale,-scale,scale,-10000,10000);
-       glTranslatef(0.0, 0.0, -2.5*scale);
+       glTranslatef(0.0, 0.0, -dist);
        glRotatef(-45, 1, 0, 0);
 
        return FALSE;