Identified task and sprite fields related to battle weather animations

Named task and sprite fields related to the animations for Hail, Rain Dance, and Sandstorm.

src/battle_anim_rock.c

@@ -388,6 +388,11 @@ static void AnimParticleInVortex_Step(struct Sprite *sprite)
     }
 }
 
+#define tBlendTimer     data[10]
+#define tBlend          data[11]
+#define tFullAlphaTimer data[11] // not a typo; this data field is used for multiple purposes
+#define tState          data[12]
+
 void AnimTask_LoadSandstormBackground(u8 taskId)
 {
     int var0;
@@ -430,45 +435,45 @@ static void AnimTask_LoadSandstormBackground_Step(u8 taskId)
 
     gBattle_BG1_Y += -1;
 
-    switch (gTasks[taskId].data[12])
+    switch (gTasks[taskId].tState)
     {
     case 0:
-        if (++gTasks[taskId].data[10] == 4)
+        if (++gTasks[taskId].tBlendTimer == 4)
         {
-            gTasks[taskId].data[10] = 0;
-            gTasks[taskId].data[11]++;
-            SetGpuReg(REG_OFFSET_BLDALPHA, BLDALPHA_BLEND(gTasks[taskId].data[11], 16 - gTasks[taskId].data[11]));
-            if (gTasks[taskId].data[11] == 7)
+            gTasks[taskId].tBlendTimer = 0;
+            gTasks[taskId].tBlend++;
+            SetGpuReg(REG_OFFSET_BLDALPHA, BLDALPHA_BLEND(gTasks[taskId].tBlend, 16 - gTasks[taskId].tBlend));
+            if (gTasks[taskId].tBlend == 7)
             {
-                gTasks[taskId].data[12]++;
-                gTasks[taskId].data[11] = 0;
+                gTasks[taskId].tState++;
+                gTasks[taskId].tFullAlphaTimer = 0;
             }
         }
         break;
     case 1:
-        if (++gTasks[taskId].data[11] == 101)
+        if (++gTasks[taskId].tFullAlphaTimer == 101)
         {
-            gTasks[taskId].data[11] = 7;
-            gTasks[taskId].data[12]++;
+            gTasks[taskId].tBlend = 7;
+            gTasks[taskId].tState++;
         }
         break;
     case 2:
-        if (++gTasks[taskId].data[10] == 4)
+        if (++gTasks[taskId].tBlendTimer == 4)
         {
-            gTasks[taskId].data[10] = 0;
-            gTasks[taskId].data[11]--;
-            SetGpuReg(REG_OFFSET_BLDALPHA, BLDALPHA_BLEND(gTasks[taskId].data[11], 16 - gTasks[taskId].data[11]));
-            if (gTasks[taskId].data[11] == 0)
+            gTasks[taskId].tBlendTimer = 0;
+            gTasks[taskId].tBlend--;
+            SetGpuReg(REG_OFFSET_BLDALPHA, BLDALPHA_BLEND(gTasks[taskId].tBlend, 16 - gTasks[taskId].tBlend));
+            if (gTasks[taskId].tBlend == 0)
             {
-                gTasks[taskId].data[12]++;
-                gTasks[taskId].data[11] = 0;
+                gTasks[taskId].tState++;
+                gTasks[taskId].tFullAlphaTimer = 0;
             }
         }
         break;
     case 3:
         GetBattleAnimBg1Data(&animBg);
         ClearBattleAnimBg(animBg.bgId);
-        gTasks[taskId].data[12]++;
+        gTasks[taskId].tState++;
         break;
     case 4:
         if (!IsContest())
@@ -484,21 +489,36 @@ static void AnimTask_LoadSandstormBackground_Step(u8 taskId)
     }
 }
 
+#undef tBlendTimer
+#undef tBlend
+#undef tFullAlphaTimer
+#undef tState
+
 // Animates the sprites that fly diagonally across the screen
 // in Sandstorm and Heat Wave.
-// arg 0: initial y pixel offset
-// arg 1: projectile speed
-// arg 2: y pixel drop
-// arg 3: ??? unknown (possibly a color bit)
+
+#define sState       data[0]
+#define sVelocityX   data[1] // 256ths of a pixel // init'd from gBattleAnimArgs[1]
+#define sVelocityY   data[2] // 256ths of a pixel // init'd from gBattleAnimArgs[2]
+#define sFractionalX data[3] // 256ths of a pixel
+#define sFractionalY data[4] // 256ths of a pixel
+#define sMirroredX   data[5] // init'd from gBattleAnimArgs[3]
+
+// The fields named "velocity" are arguably more like "acceleration," 
+// and the fields named "fractional" are arguably more like "velocity."
+//
+// ...is what I WOULD say if the "fractional" fields weren't AND'd with 
+// 0xFF after every frame.
+
 static void AnimFlyingSandCrescent(struct Sprite *sprite)
 {
-    if (sprite->data[0] == 0)
+    if (sprite->sState == 0)
     {
         if (gBattleAnimArgs[3] != 0 && GetBattlerSide(gBattleAnimAttacker) != B_SIDE_PLAYER)
         {
             sprite->x = DISPLAY_WIDTH + 64;
             gBattleAnimArgs[1] = -gBattleAnimArgs[1];
-            sprite->data[5] = 1;
+            sprite->sMirroredX = 1;
             sprite->oam.matrixNum = ST_OAM_HFLIP;
         }
         else
@@ -508,18 +528,18 @@ static void AnimFlyingSandCrescent(struct Sprite *sprite)
 
         sprite->y = gBattleAnimArgs[0];
         SetSubspriteTables(sprite, sFlyingSandSubspriteTable);
-        sprite->data[1] = gBattleAnimArgs[1];
-        sprite->data[2] = gBattleAnimArgs[2];
-        sprite->data[0]++;
+        sprite->sVelocityX = gBattleAnimArgs[1];
+        sprite->sVelocityY = gBattleAnimArgs[2];
+        sprite->sState++;
     }
     else
     {
-        sprite->data[3] += sprite->data[1];
-        sprite->data[4] += sprite->data[2];
-        sprite->x2 += (sprite->data[3] >> 8);
-        sprite->y2 += (sprite->data[4] >> 8);
-        sprite->data[3] &= 0xFF;
-        sprite->data[4] &= 0xFF;
+        sprite->sFractionalX += sprite->sVelocityX;
+        sprite->sFractionalY += sprite->sVelocityY;
+        sprite->x2 += (sprite->sFractionalX >> 8);
+        sprite->y2 += (sprite->sFractionalY >> 8);
+        sprite->sFractionalX &= 0xFF;
+        sprite->sFractionalY &= 0xFF;
 
         if (sprite->data[5] == 0)
         {
@@ -535,6 +555,13 @@ static void AnimFlyingSandCrescent(struct Sprite *sprite)
     }
 }
 
+#undef sState
+#undef sVelocityX
+#undef sVelocityY
+#undef sFractionalX
+#undef sFractionalY
+#undef sMirroredX
+
 // Animates the rising rocks in Ancient Power.
 // arg 0: initial x pixel offset
 // arg 1: initial y pixel offset