1 files changed, 796 insertions, 0 deletions
diff --git a/src/field/field_ground_effect.c b/src/field/field_ground_effect.c
new file mode 100644
index 000000000..5af8ea3e3
--- /dev/null
+++ b/src/field/field_ground_effect.c
@@ -0,0 +1,796 @@
+#include "global.h"
+#include "field_ground_effect.h"
+#include "field_effect.h"
+#include "field_effect_helpers.h"
+#include "field_map_obj_helpers.h"
+#include "fieldmap.h"
+#include "metatile_behavior.h"
+
+static void nullsub(struct MapObject *mapObj, struct Sprite *sprite, u8);
+static void DoTracksGroundEffect_Footprints(struct MapObject *mapObj, struct Sprite *sprite, u8);
+static void DoTracksGroundEffect_BikeTireTracks(
+    struct MapObject *mapObj, struct Sprite *sprite, u8);
+void GroundEffect_SpawnOnTallGrass(struct MapObject *mapObj, struct Sprite *sprite);
+void sub_8063E94(struct MapObject *mapObj, struct Sprite *sprite);
+void sub_8063EE0(struct MapObject *mapObj, struct Sprite *sprite);
+void sub_8063F2C(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_WaterReflection(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_IceReflection(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_FlowingWater(struct MapObject *mapObj, struct Sprite *sprite);
+void sub_8063FA0(struct MapObject *mapObj, struct Sprite *sprite);
+void sub_8063FCC(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_Ripple(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_StepOnPuddle(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_SandPile(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_JumpOnTallGrass(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_JumpOnLongGrass(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_JumpOnShallowWater(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_JumpOnWater(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_JumpLandingDust(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_ShortGrass(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_HotSprings(struct MapObject *mapObj, struct Sprite *sprite);
+void GroundEffect_Seaweed(struct MapObject *mapObj, struct Sprite *sprite);
+u8 GetReflectionTypeByMetatileBehavior(u32 behavior);
+
+static void GetAllGroundEffectFlags_OnSpawn(struct MapObject *mapObj, u32 *flags)
+{
+    FieldObjectUpdateMetatileBehaviors(mapObj);
+    GetGroundEffectFlags_Reflection(mapObj, flags);
+    GetGroundEffectFlags_TallGrassOnSpawn(mapObj, flags);
+    GetGroundEffectFlags_LongGrassOnSpawn(mapObj, flags);
+    GetGroundEffectFlags_SandPile(mapObj, flags);
+    GetGroundEffectFlags_ShallowFlowingWater(mapObj, flags);
+    GetGroundEffectFlags_ShortGrass(mapObj, flags);
+    GetGroundEffectFlags_HotSprings(mapObj, flags);
+}
+
+static void GetAllGroundEffectFlags_OnBeginStep(struct MapObject *mapObj, u32 *flags)
+{
+    FieldObjectUpdateMetatileBehaviors(mapObj);
+    GetGroundEffectFlags_Reflection(mapObj, flags);
+    GetGroundEffectFlags_TallGrassOnBeginStep(mapObj, flags);
+    GetGroundEffectFlags_LongGrassOnBeginStep(mapObj, flags);
+    GetGroundEffectFlags_Tracks(mapObj, flags);
+    GetGroundEffectFlags_SandPile(mapObj, flags);
+    GetGroundEffectFlags_ShallowFlowingWater(mapObj, flags);
+    GetGroundEffectFlags_Puddle(mapObj, flags);
+    GetGroundEffectFlags_ShortGrass(mapObj, flags);
+    GetGroundEffectFlags_HotSprings(mapObj, flags);
+}
+
+static void GetAllGroundEffectFlags_OnFinishStep(struct MapObject *mapObj, u32 *flags)
+{
+    FieldObjectUpdateMetatileBehaviors(mapObj);
+    GetGroundEffectFlags_ShallowFlowingWater(mapObj, flags);
+    GetGroundEffectFlags_SandPile(mapObj, flags);
+    GetGroundEffectFlags_Puddle(mapObj, flags);
+    GetGroundEffectFlags_Ripple(mapObj, flags);
+    GetGroundEffectFlags_ShortGrass(mapObj, flags);
+    GetGroundEffectFlags_HotSprings(mapObj, flags);
+    GetGroundEffectFlags_Seaweed(mapObj, flags);
+    GetGroundEffectFlags_JumpLanding(mapObj, flags);
+}
+
+void FieldObjectUpdateMetatileBehaviors(struct MapObject *mapObj)
+{
+    mapObj->mapobj_unk_1F = MapGridGetMetatileBehaviorAt(mapObj->coords3.x, mapObj->coords3.y);
+    mapObj->mapobj_unk_1E = MapGridGetMetatileBehaviorAt(mapObj->coords2.x, mapObj->coords2.y);
+}
+
+void GetGroundEffectFlags_Reflection(struct MapObject *mapObj, u32 *flags)
+{
+    u32 reflectionFlags[2] = { 0x00000020, 0x00000010 };
+    u8 type = FieldObjectCheckForReflectiveSurface(mapObj);
+
+    if (type)
+    {
+        if (!mapObj->mapobj_bit_17)
+        {
+            mapObj->mapobj_bit_17 = 0;
+            mapObj->mapobj_bit_17 = 1;
+            *flags |= reflectionFlags[type - 1];
+        }
+    }
+    else
+    {
+        mapObj->mapobj_bit_17 = 0;
+    }
+}
+
+void GetGroundEffectFlags_TallGrassOnSpawn(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsTallGrass(mapObj->mapobj_unk_1E))
+        *flags |= 0x1;
+}
+
+void GetGroundEffectFlags_TallGrassOnBeginStep(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsTallGrass(mapObj->mapobj_unk_1E))
+        *flags |= 0x2;
+}
+
+void GetGroundEffectFlags_LongGrassOnSpawn(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsLongGrass(mapObj->mapobj_unk_1E))
+        *flags |= 0x4;
+}
+
+void GetGroundEffectFlags_LongGrassOnBeginStep(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsLongGrass(mapObj->mapobj_unk_1E))
+        *flags |= 0x8;
+}
+
+void GetGroundEffectFlags_Tracks(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsDeepSand(mapObj->mapobj_unk_1F))
+    {
+        *flags |= 0x100;
+    }
+    else if (MetatileBehavior_IsSandOrDeepSand(mapObj->mapobj_unk_1F)
+             || MetatileBehavior_IsUnusedFootprintMetatile(mapObj->mapobj_unk_1F))
+    {
+        *flags |= 0x80;
+    }
+}
+
+void GetGroundEffectFlags_SandPile(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsDeepSand(mapObj->mapobj_unk_1E)
+        && MetatileBehavior_IsDeepSand(mapObj->mapobj_unk_1F))
+    {
+        if (!mapObj->mapobj_bit_20)
+        {
+            mapObj->mapobj_bit_20 = 0;
+            mapObj->mapobj_bit_20 = 1;
+            *flags |= 0x800;
+        }
+    }
+    else
+    {
+        mapObj->mapobj_bit_20 = 0;
+    }
+}
+
+void GetGroundEffectFlags_ShallowFlowingWater(struct MapObject *mapObj, u32 *flags)
+{
+    if ((MetatileBehavior_IsShallowFlowingWater(mapObj->mapobj_unk_1E)
+         && MetatileBehavior_IsShallowFlowingWater(mapObj->mapobj_unk_1F))
+        || (MetatileBehavior_IsPacifidlogLog(mapObj->mapobj_unk_1E)
+            && MetatileBehavior_IsPacifidlogLog(mapObj->mapobj_unk_1F)))
+    {
+        if (!mapObj->mapobj_bit_19)
+        {
+            mapObj->mapobj_bit_19 = 0;
+            mapObj->mapobj_bit_19 = 1;
+            *flags |= 0x40;
+        }
+    }
+    else
+    {
+        mapObj->mapobj_bit_19 = 0;
+    }
+}
+
+void GetGroundEffectFlags_Puddle(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsPuddle(mapObj->mapobj_unk_1E)
+        && MetatileBehavior_IsPuddle(mapObj->mapobj_unk_1F))
+    {
+        *flags |= 0x400;
+    }
+}
+
+void GetGroundEffectFlags_Ripple(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_HasRipples(mapObj->mapobj_unk_1E))
+        *flags |= 0x200;
+}
+
+void GetGroundEffectFlags_ShortGrass(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsShortGrass(mapObj->mapobj_unk_1E)
+        && MetatileBehavior_IsShortGrass(mapObj->mapobj_unk_1F))
+    {
+        if (!mapObj->mapobj_bit_18)
+        {
+            mapObj->mapobj_bit_18 = 0;
+            mapObj->mapobj_bit_18 = 1;
+            *flags |= 0x20000;
+        }
+    }
+    else
+    {
+        mapObj->mapobj_bit_18 = 0;
+    }
+}
+
+void GetGroundEffectFlags_HotSprings(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsHotSprings(mapObj->mapobj_unk_1E)
+        && MetatileBehavior_IsHotSprings(mapObj->mapobj_unk_1F))
+    {
+        if (!mapObj->mapobj_bit_21)
+        {
+            mapObj->mapobj_bit_21 = 0;
+            mapObj->mapobj_bit_21 = 1;
+            *flags |= 0x40000;
+        }
+    }
+    else
+    {
+        mapObj->mapobj_bit_21 = 0;
+    }
+}
+
+void GetGroundEffectFlags_Seaweed(struct MapObject *mapObj, u32 *flags)
+{
+    if (MetatileBehavior_IsSeaweed(mapObj->mapobj_unk_1E))
+        *flags |= 0x80000;
+}
+
+void GetGroundEffectFlags_JumpLanding(struct MapObject *mapObj, u32 *flags)
+{
+    typedef bool8 (*MetatileFunc)(u8);
+
+    static const MetatileFunc metatileFuncs[] = {
+        MetatileBehavior_IsTallGrass,
+        MetatileBehavior_IsLongGrass,
+        MetatileBehavior_IsPuddle,
+        MetatileBehavior_IsSurfableWaterOrUnderwater,
+        MetatileBehavior_IsShallowFlowingWater,
+        MetatileBehavior_IsATile,
+    };
+
+    static const u32 jumpLandingFlags[] = {
+        0x00001000, // Landing in tall grass
+        0x00002000, // Landing in long grass
+        0x00004000, // Landing on puddle
+        0x00008000, // Landing on surfable water or underwater
+        0x00004000, // Landing on shallow flowing water
+        0x00010000, // Landing on any other type of ground
+    };
+
+    if (mapObj->mapobj_bit_5 && !mapObj->mapobj_bit_25)
+    {
+        u8 i;
+
+        for (i = 0; i < 6; i++)
+        {
+            if (metatileFuncs[i](mapObj->mapobj_unk_1E))
+            {
+                *flags |= jumpLandingFlags[i];
+                return;
+            }
+        }
+    }
+}
+
+u8 FieldObjectCheckForReflectiveSurface(struct MapObject *mapObj)
+{
+    const struct MapObjectGraphicsInfo *info = GetFieldObjectGraphicsInfo(mapObj->graphicsId);
+
+    // ceil div by tile width?
+    s16 width = (info->width + 8) >> 4;
+    s16 height = (info->height + 8) >> 4;
+    s16 i;
+    s16 j;
+    u8 result;
+    u8 b;
+    s16 one;
+
+#define RETURN_REFLECTION_TYPE_AT(x, y)              \
+    b = MapGridGetMetatileBehaviorAt(x, y);          \
+    result = GetReflectionTypeByMetatileBehavior(b); \
+    if (result != 0)                                 \
+        return result;
+
+    for (i = 0, one = 1; i < height; i++)
+    {
+        RETURN_REFLECTION_TYPE_AT(mapObj->coords2.x, mapObj->coords2.y + one + i)
+        RETURN_REFLECTION_TYPE_AT(mapObj->coords3.x, mapObj->coords3.y + one + i)
+        for (j = 1; j < width; j++)
+        {
+            RETURN_REFLECTION_TYPE_AT(mapObj->coords2.x + j, mapObj->coords2.y + one + i)
+            RETURN_REFLECTION_TYPE_AT(mapObj->coords2.x - j, mapObj->coords2.y + one + i)
+            RETURN_REFLECTION_TYPE_AT(mapObj->coords3.x + j, mapObj->coords3.y + one + i)
+            RETURN_REFLECTION_TYPE_AT(mapObj->coords3.x - j, mapObj->coords3.y + one + i)
+        }
+    }
+    return 0;
+
+#undef RETURN_REFLECTION_TYPE_AT
+}
+
+u8 GetReflectionTypeByMetatileBehavior(u32 behavior)
+{
+    if (MetatileBehavior_IsIce(behavior))
+        return 1;
+    else if (MetatileBehavior_IsReflective(behavior))
+        return 2;
+    else
+        return 0;
+}
+
+u8 GetLedgeJumpDirection(s16 x, s16 y, u8 z)
+{
+    static bool8 (*const unknown_08376040[])(u8) = {
+        MetatileBehavior_IsJumpSouth,
+        MetatileBehavior_IsJumpNorth,
+        MetatileBehavior_IsJumpWest,
+        MetatileBehavior_IsJumpEast,
+    };
+
+    u8 b;
+    u8 index = z;
+
+    if (index == 0)
+        return 0;
+    else if (index > 4)
+        index -= 4;
+
+    index--;
+    b = MapGridGetMetatileBehaviorAt(x, y);
+
+    if (unknown_08376040[index](b) == 1)
+        return index + 1;
+
+    return 0;
+}
+
+void FieldObjectSetSpriteOamTableForLongGrass(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    if (mapObj->mapobj_bit_4)
+        return;
+
+    if (!MetatileBehavior_IsLongGrass(mapObj->mapobj_unk_1E))
+        return;
+
+    if (!MetatileBehavior_IsLongGrass(mapObj->mapobj_unk_1F))
+        return;
+
+    sprite->subspriteTableNum = 4;
+
+    if (ZCoordToPriority(mapObj->elevation) == 1)
+        sprite->subspriteTableNum = 5;
+}
+
+bool8 IsZCoordMismatchAt(u8 z, s16 x, s16 y)
+{
+    u8 mapZ;
+
+    if (z == 0)
+        return FALSE;
+
+    mapZ = MapGridGetZCoordAt(x, y);
+
+    if (mapZ == 0 || mapZ == 0xF)
+        return FALSE;
+
+    if (mapZ != z)
+        return TRUE;
+
+    return FALSE;
+}
+
+static const u8 sUnknown_08376050[] = {
+    0x73, 0x73, 0x53, 0x73, 0x53, 0x73, 0x53, 0x73, 0x53, 0x73, 0x53, 0x73, 0x53, 0x00, 0x00, 0x73
+};
+
+// Each byte corresponds to a sprite priority for a field object.
+// This is directly the inverse of gFieldObjectPriorities_08376070.
+static const u8 sFieldObjectPriorities_08376060[] = {
+    2, 2, 2, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 0, 0, 2
+};
+
+// Each byte corresponds to a sprite priority for a field object.
+// This is the inverse of gFieldObjectPriorities_08376060.
+// 1 = Above player sprite
+// 2 = Below player sprite
+static const u8 sFieldObjectPriorities_08376070[] = {
+    1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 0, 0, 1,
+};
+
+void FieldObjectUpdateZCoordAndPriority(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    if (mapObj->mapobj_bit_26)
+        return;
+
+    FieldObjectUpdateZCoord(mapObj);
+
+    sprite->subspriteTableNum = sFieldObjectPriorities_08376070[mapObj->elevation];
+    sprite->oam.priority = sFieldObjectPriorities_08376060[mapObj->elevation];
+}
+
+void InitObjectPriorityByZCoord(struct Sprite *sprite, u8 z)
+{
+    sprite->subspriteTableNum = sFieldObjectPriorities_08376070[z];
+    sprite->oam.priority = sFieldObjectPriorities_08376060[z];
+}
+
+u8 ZCoordToPriority(u8 z)
+{
+    return sFieldObjectPriorities_08376060[z];
+}
+
+void FieldObjectUpdateZCoord(struct MapObject *mapObj)
+{
+    u8 z = MapGridGetZCoordAt(mapObj->coords2.x, mapObj->coords2.y);
+    u8 z2 = MapGridGetZCoordAt(mapObj->coords3.x, mapObj->coords3.y);
+
+    if (z == 0xF || z2 == 0xF)
+        return;
+
+    mapObj->mapobj_unk_0B_0 = z;
+
+    if (z != 0 && z != 0xF)
+        mapObj->elevation = z;
+}
+
+void SetObjectSubpriorityByZCoord(u8 a, struct Sprite *sprite, u8 b)
+{
+    s32 tmp = sprite->centerToCornerVecY;
+    u32 tmpa = *(u16 *)&sprite->pos1.y;
+    u32 tmpb = *(u16 *)&gSpriteCoordOffsetY;
+    s32 tmp2 = (tmpa - tmp) + tmpb;
+    u16 tmp3 = (0x10 - ((((u32)tmp2 + 8) & 0xFF) >> 4)) * 2;
+    sprite->subpriority = tmp3 + sUnknown_08376050[a] + b;
+}
+
+void FieldObjectUpdateSubpriority(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    if (mapObj->mapobj_bit_26)
+        return;
+
+    SetObjectSubpriorityByZCoord(mapObj->elevation, sprite, 1);
+}
+
+bool8 AreZCoordsCompatible(u8 a, u8 b)
+{
+    if (a == 0 || b == 0)
+        return TRUE;
+
+    if (a != b)
+        return FALSE;
+
+    return TRUE;
+}
+
+void GroundEffect_SpawnOnTallGrass(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u8 *ptr;
+
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = 2;
+    gFieldEffectArguments[4] = (mapObj->localId << 8) | mapObj->mapNum;
+    gFieldEffectArguments[5] = mapObj->mapGroup;
+
+    ptr = (u8 *)&gSaveBlock1;
+    gFieldEffectArguments[6] = ((u8)gSaveBlock1.location.mapNum << 8)
+                         | (u8)gSaveBlock1.location.mapGroup;
+
+    gFieldEffectArguments[7] = 1;
+    FieldEffectStart(FLDEFF_TALL_GRASS);
+}
+
+void sub_8063E94(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u8 *ptr;
+
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = 2;
+    gFieldEffectArguments[4] = (mapObj->localId << 8) | mapObj->mapNum;
+    gFieldEffectArguments[5] = mapObj->mapGroup;
+
+    ptr = (u8 *)&gSaveBlock1;
+    gFieldEffectArguments[6] = ((u8)gSaveBlock1.location.mapNum << 8)
+                         | (u8)gSaveBlock1.location.mapGroup;
+
+    gFieldEffectArguments[7] = 0;
+    FieldEffectStart(FLDEFF_TALL_GRASS);
+}
+
+void sub_8063EE0(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u8 *ptr;
+
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = 2;
+    gFieldEffectArguments[4] = (mapObj->localId << 8) | mapObj->mapNum;
+    gFieldEffectArguments[5] = mapObj->mapGroup;
+
+    ptr = (u8 *)&gSaveBlock1;
+    gFieldEffectArguments[6] = ((u8)gSaveBlock1.location.mapNum << 8)
+                         | (u8)gSaveBlock1.location.mapGroup;
+
+    gFieldEffectArguments[7] = 1;
+    FieldEffectStart(FLDEFF_LONG_GRASS);
+}
+
+void sub_8063F2C(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u8 *ptr;
+
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = 2;
+    gFieldEffectArguments[4] = (mapObj->localId << 8) | mapObj->mapNum;
+    gFieldEffectArguments[5] = mapObj->mapGroup;
+
+    ptr = (u8 *)&gSaveBlock1;
+    gFieldEffectArguments[6] = ((u8)gSaveBlock1.location.mapNum << 8)
+                         | (u8)gSaveBlock1.location.mapGroup;
+
+    gFieldEffectArguments[7] = 0;
+    FieldEffectStart(FLDEFF_LONG_GRASS);
+}
+
+void GroundEffect_WaterReflection(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    SetUpReflection(mapObj, sprite, 0);
+}
+
+void GroundEffect_IceReflection(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    SetUpReflection(mapObj, sprite, 1);
+}
+
+void GroundEffect_FlowingWater(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    oe_exec_and_other_stuff(FLDEFF_FEET_IN_FLOWING_WATER, mapObj);
+}
+
+static void (*const gUnknown_08376080[])(struct MapObject *mapObj, struct Sprite *sprite, u8 a) = {
+    nullsub, DoTracksGroundEffect_Footprints, DoTracksGroundEffect_BikeTireTracks,
+};
+
+void sub_8063FA0(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    const struct MapObjectGraphicsInfo *info = GetFieldObjectGraphicsInfo(mapObj->graphicsId);
+    gUnknown_08376080[info->tracks](mapObj, sprite, 0);
+}
+
+void sub_8063FCC(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    const struct MapObjectGraphicsInfo *info = GetFieldObjectGraphicsInfo(mapObj->graphicsId);
+    gUnknown_08376080[info->tracks](mapObj, sprite, 1);
+}
+
+static void nullsub(struct MapObject *mapObj, struct Sprite *sprite, u8 a)
+{
+}
+
+static void DoTracksGroundEffect_Footprints(struct MapObject *mapObj, struct Sprite *sprite, u8 a)
+{
+    // First half-word is a Field Effect script id. (gFieldEffectScriptPointers)
+    u16 sandFootprints_FieldEffectData[2] = {
+            FLDEFF_SAND_FOOTPRINTS,
+            FLDEFF_DEEP_SAND_FOOTPRINTS
+    };
+
+    gFieldEffectArguments[0] = mapObj->coords3.x;
+    gFieldEffectArguments[1] = mapObj->coords3.y;
+    gFieldEffectArguments[2] = 149;
+    gFieldEffectArguments[3] = 2;
+    gFieldEffectArguments[4] = mapObj->mapobj_unk_18;
+    FieldEffectStart(sandFootprints_FieldEffectData[a]);
+}
+
+static void DoTracksGroundEffect_BikeTireTracks(
+    struct MapObject *mapObj, struct Sprite *sprite, u8 a)
+{
+    //  Specifies which bike track shape to show next.
+    //  For example, when the bike turns from up to right, it will show
+    //  a track that curves to the right.
+    //  Each 4-byte row corresponds to the initial direction of the bike, and
+    //  each byte in that row is for the next direction of the bike in the order
+    //  of down, up, left, right.
+    static const u8 bikeTireTracks_Transitions[4][4] = {
+        1, 2, 7, 8,
+        1, 2, 6, 5,
+        5, 8, 3, 4,
+        6, 7, 3, 4,
+    };
+
+    if (mapObj->coords2.x != mapObj->coords3.x || mapObj->coords2.y != mapObj->coords3.y)
+    {
+        gFieldEffectArguments[0] = mapObj->coords3.x;
+        gFieldEffectArguments[1] = mapObj->coords3.y;
+        gFieldEffectArguments[2] = 149;
+        gFieldEffectArguments[3] = 2;
+        gFieldEffectArguments[4] =
+            bikeTireTracks_Transitions[mapObj->mapobj_unk_20][mapObj->mapobj_unk_18 - 5];
+        FieldEffectStart(FLDEFF_BIKE_TIRE_TRACKS);
+    }
+}
+
+void GroundEffect_Ripple(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    DoRippleFieldEffect(mapObj, sprite);
+}
+
+void GroundEffect_StepOnPuddle(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    oe_exec_and_other_stuff(FLDEFF_SPLASH, mapObj);
+}
+
+void GroundEffect_SandPile(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    oe_exec_and_other_stuff(FLDEFF_SAND_PILE, mapObj);
+}
+
+void GroundEffect_JumpOnTallGrass(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u8 spriteId;
+
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = 2;
+    FieldEffectStart(FLDEFF_JUMP_TALL_GRASS);
+
+    spriteId = sub_8126FF0(
+        mapObj->localId, mapObj->mapNum, mapObj->mapGroup, mapObj->coords2.x, mapObj->coords2.y);
+
+    if (spriteId == MAX_SPRITES)
+        GroundEffect_SpawnOnTallGrass(mapObj, sprite);
+}
+
+void GroundEffect_JumpOnLongGrass(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = 2;
+    FieldEffectStart(FLDEFF_JUMP_LONG_GRASS);
+}
+
+void GroundEffect_JumpOnShallowWater(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = sprite->oam.priority;
+    FieldEffectStart(FLDEFF_JUMP_SMALL_SPLASH);
+}
+
+void GroundEffect_JumpOnWater(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = sprite->oam.priority;
+    FieldEffectStart(FLDEFF_JUMP_BIG_SPLASH);
+}
+
+void GroundEffect_JumpLandingDust(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    gFieldEffectArguments[2] = mapObj->elevation;
+    gFieldEffectArguments[3] = sprite->oam.priority;
+    FieldEffectStart(FLDEFF_DUST);
+}
+
+void GroundEffect_ShortGrass(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    oe_exec_and_other_stuff(FLDEFF_SHORT_GRASS, mapObj);
+}
+
+void GroundEffect_HotSprings(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    oe_exec_and_other_stuff(FLDEFF_HOT_SPRINGS_WATER, mapObj);
+}
+
+void GroundEffect_Seaweed(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    gFieldEffectArguments[0] = mapObj->coords2.x;
+    gFieldEffectArguments[1] = mapObj->coords2.y;
+    FieldEffectStart(FLDEFF_BUBBLES);
+}
+
+static void (*const gUnknown_083760A0[])(struct MapObject *mapObj, struct Sprite *sprite) = {
+    GroundEffect_SpawnOnTallGrass,
+    sub_8063E94,
+    sub_8063EE0,
+    sub_8063F2C,
+    GroundEffect_WaterReflection,
+    GroundEffect_IceReflection,
+    GroundEffect_FlowingWater,
+    sub_8063FA0,
+    sub_8063FCC,
+    GroundEffect_Ripple,
+    GroundEffect_StepOnPuddle,
+    GroundEffect_SandPile,
+    GroundEffect_JumpOnTallGrass,
+    GroundEffect_JumpOnLongGrass,
+    GroundEffect_JumpOnShallowWater,
+    GroundEffect_JumpOnWater,
+    GroundEffect_JumpLandingDust,
+    GroundEffect_ShortGrass,
+    GroundEffect_HotSprings,
+    GroundEffect_Seaweed
+};
+
+void sub_8064218(struct MapObject *mapObj, struct Sprite *sprite, u32 flags)
+{
+    u8 i;
+    for (i = 0; i < ARRAY_COUNT(gUnknown_083760A0); i++, flags >>= 1)
+        if (flags & 1)
+            gUnknown_083760A0[i](mapObj, sprite);
+}
+
+void filters_out_some_ground_effects(struct MapObject *mapObj, u32 *flags)
+{
+    if (mapObj->mapobj_bit_4)
+    {
+        mapObj->mapobj_bit_18 = 0;
+        mapObj->mapobj_bit_20 = 0;
+        mapObj->mapobj_bit_19 = 0;
+        mapObj->mapobj_bit_21 = 0;
+        *flags &= 0xFFF9F7BD;
+    }
+}
+
+void FilterOutStepOnPuddleGroundEffectIfJumping(struct MapObject *mapObj, u32 *flags)
+{
+    if (mapObj->mapobj_bit_5)
+        *flags &= 0xFFFFFBFF;
+}
+
+void DoGroundEffects_OnSpawn(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u32 flags;
+
+    if (mapObj->mapobj_bit_2)
+    {
+        flags = 0;
+        FieldObjectUpdateZCoordAndPriority(mapObj, sprite);
+        GetAllGroundEffectFlags_OnSpawn(mapObj, &flags);
+        FieldObjectSetSpriteOamTableForLongGrass(mapObj, sprite);
+        sub_8064218(mapObj, sprite, flags);
+        mapObj->mapobj_bit_2 = 0;
+        mapObj->mapobj_bit_4 = 0;
+    }
+}
+
+void DoGroundEffects_OnBeginStep(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u32 flags;
+
+    if (mapObj->mapobj_bit_2)
+    {
+        flags = 0;
+        FieldObjectUpdateZCoordAndPriority(mapObj, sprite);
+        GetAllGroundEffectFlags_OnBeginStep(mapObj, &flags);
+        FieldObjectSetSpriteOamTableForLongGrass(mapObj, sprite);
+        filters_out_some_ground_effects(mapObj, &flags);
+        sub_8064218(mapObj, sprite, flags);
+        mapObj->mapobj_bit_2 = 0;
+        mapObj->mapobj_bit_4 = 0;
+    }
+}
+
+void DoGroundEffects_OnFinishStep(struct MapObject *mapObj, struct Sprite *sprite)
+{
+    u32 flags;
+
+    if (mapObj->mapobj_bit_3)
+    {
+        flags = 0;
+        FieldObjectUpdateZCoordAndPriority(mapObj, sprite);
+        GetAllGroundEffectFlags_OnFinishStep(mapObj, &flags);
+        FieldObjectSetSpriteOamTableForLongGrass(mapObj, sprite);
+        FilterOutStepOnPuddleGroundEffectIfJumping(mapObj, &flags);
+        sub_8064218(mapObj, sprite, flags);
+        mapObj->mapobj_bit_3 = 0;
+        mapObj->mapobj_bit_5 = 0;
+    }
+}