Fix flame artifacts showing up after days

Due to floating point precision problems the flames started to look
weird after some days. With this change in place, we just reset the time
once or place per day to stop this from happening.

libloadviz/src/renderer.rs

@@ -35,6 +35,14 @@ impl Renderer {
             // FIXME: Draw something nice?
             return;
         }
+
+        // Too high values make the flames look like they have JPEG artifacts.
+        //
+        // Experiments showed that 14 days was really bad. 7 days was not bad.
+        // So let's cap it at somewhere around 70% of one day so that the cut
+        // comes at different times every day.
+        let dt_seconds = dt_seconds % (3600.0 * 17.3);
+
         let viz_loads = mirror_sort(currently_displayed_loads);
 
         for pixel_x in 0..width {