main loop: Fade correctly when simulation runs fast

[sdl-planets] / main.c

diff --git a/main.c b/main.c
index 87150f8f6d939e6f5e4ed6e927dcb3989acc03dd..7256fa48c3bac21ade6972d20b38cf684b2564b0 100644 (file)
--- a/main.c
+++ b/main.c
@@ -168,7 +168,7 @@ static void loop(SDL_Surface *screen, int num_of_planets, double total_mass,
        int last_framecount = 0, last_step_count = 0;
        unsigned long old_ticks, ticks = 0, last_frame_tick = 0;
        unsigned long step_count = 0;
-       double last_fps = 0, last_sps = 0;
+       double last_fps = 0, last_sps = 0, fade_amount;
        double step_time = 0, true_time = 0;
 
        init_camera(&camera);
@@ -221,14 +221,14 @@ static void loop(SDL_Surface *screen, int num_of_planets, double total_mass,
                if (last_frame_tick + (1000 * 1000) / MAX_FPS > ticks)
                        continue;
 
-               last_frame_tick = ticks;
-
                SDL_LockSurface(screen);
 
                if (status.tracers_enabled &&
                    !camera.speed.x && !camera.speed.y &&
                    camera.zoom_rate == 1) {
-                       fade_buf(screen, 10 * true_time);
+                       fade_amount = (ticks - last_frame_tick) /
+                               (1000 * 1000.0) * 20;
+                       fade_buf(screen, fade_amount);
                } else {
                        clear_buf(screen);
                }
@@ -242,6 +242,8 @@ static void loop(SDL_Surface *screen, int num_of_planets, double total_mass,
 
                SDL_Flip(screen);
 
+               last_frame_tick = ticks;
+
                if (last_fps_time + (500 * 1000) < ticks) {
                        last_framecount = framecount - last_framecount;
                        last_fps = last_framecount * 1000 * 1000 /