Fix some ghost stuff

TODO.txt

@@ -1,5 +1,6 @@
 =========== GENERAL ==============
 
+- ghost visible distance
 - test if the replay stretching works
 - replay validation
 - ghosts: if the replay for the ghost is too long (too many samples for the

game.h

@@ -350,7 +350,7 @@ void LCR_gameResetRun(uint8_t replay, uint8_t ghost)
   LCR_game.runTimeMS = 0;
 }
 
-void _LCR_gameGetNthGhostSample(unsigned int n,
+void LCR_gameGetNthGhostSample(unsigned int n,
   LCR_GameUnit position[3], LCR_GameUnit rotation[3])
 {
   n *= LCR_GHOST_SAMPLE_SIZE;
@@ -392,14 +392,14 @@ void LCR_gameGhostGetTransform(uint32_t frame,
 {
   unsigned int n = ((frame >> LCR_game.ghost.stretch) / LCR_SETTING_GHOST_STEP); 
 
-  _LCR_gameGetNthGhostSample(n % 64,position,rotation);
+  LCR_gameGetNthGhostSample(n,position,rotation);
 
   if (n < LCR_SETTING_GHOST_MAX_SAMPLES - 1)
   {
     LCR_GameUnit carTransform[6];
 
     // interpolate:
-    _LCR_gameGetNthGhostSample((n % 64) + 1,carTransform,carTransform + 3);
+    LCR_gameGetNthGhostSample(n + 1,carTransform,carTransform + 3);
 
     n = (frame >> LCR_game.ghost.stretch) % LCR_SETTING_GHOST_STEP;
 
@@ -422,6 +422,15 @@ void LCR_gameGhostGetTransform(uint32_t frame,
         / LCR_SETTING_GHOST_STEP)) % LCR_GAME_UNIT;
     }
   }
+
+  /* Small hack: at the beginning the ghost can be seen misaligned with the
+    real car due to its quantized position, here we gradually snap it to the
+    nearest 1/8th of a block (which should hit the start position) during the
+    first 16 frames. */
+  if (LCR_racing.tick < 16)
+    for (int i = 0; i < 3; ++i)
+      position[i] = position[i] + (LCR_racing.tick * (position[i] -
+      ((position[i] + LCR_GAME_UNIT / 8) / (LCR_GAME_UNIT / 4)))) / 16;
 }
 
 void _LCR_gamePrepareGhost(void)
@@ -448,7 +457,8 @@ void _LCR_gamePrepareGhost(void)
     if (LCR_racing.tick % (LCR_SETTING_GHOST_STEP << LCR_game.ghost.stretch)
       == 0 || LCR_replayHasFinished())
     {
-      LCR_racingGetCarTransform(carTransform,carTransform + 3,0);
+      LCR_racingGetCarTransform(carTransform,carTransform + 3,
+        LCR_GAME_UNIT / 2);
 
       for (int i = 0; i < 3; ++i)
       {
@@ -474,10 +484,10 @@ void _LCR_gamePrepareGhost(void)
       currentSample[4] =
         (carTransform[4] & 0x0f) | (carTransform[5] << 4);
 
+      currentSample += LCR_GHOST_SAMPLE_SIZE;
+
       if (LCR_replayHasFinished())
         break;
-
-      currentSample += LCR_GHOST_SAMPLE_SIZE;
     }
 
     LCR_racingStep(0);

racing.h

@@ -120,7 +120,7 @@ struct
   uint16_t currentEvent;
   uint16_t currentFrame;
   uint32_t achievedTime;
-} LCR_replay;
+} LCR_replay; // TODO: move inside LCR_racing?
 
 /**
   Gets times of the run in milliseconds.
@@ -326,8 +326,6 @@ int LCR_replayHasFinished(void)
   }
 
   return LCR_replay.currentEvent > LCR_replay.eventCount;
-
-//  return LCR_replay.currentEvent >= LCR_replay.eventCount;
 }
 
 /**
@@ -957,8 +955,8 @@ void LCR_racingInit(void)
 
 /**
   Gets current car transformation intended for rendering, i.e. potentially with
-  smoothing and interpolation applied to the underlying internal state in the
+  smoothing and interpolation (by LCR_GameUnits) applied to the underlying
-  physics engine.
+  internal state in the physics engine.
 */
 void LCR_racingGetCarTransform(LCR_GameUnit position[3],
   LCR_GameUnit rotation[3], LCR_GameUnit interpolationParam)