diff --git a/include/SSystem/SComponent/c_bg_s.h b/include/SSystem/SComponent/c_bg_s.h
index 9a22cc946..49c69062f 100644
--- a/include/SSystem/SComponent/c_bg_s.h
+++ b/include/SSystem/SComponent/c_bg_s.h
@@ -55,7 +55,7 @@ public:
     s32 GetTriGrp(int, int) const;
     s32 GetGrpToRoomId(int, int) const;
     cM3dGPla* GetTriPla(int, int) const;
-    bool GetTriPnt(cBgS_PolyInfo&, cXyz*, cXyz*, cXyz*) const;
+    void GetTriPnt(cBgS_PolyInfo&, cXyz*, cXyz*, cXyz*) const;
     void ShdwDraw(cBgS_ShdwDraw*);
     s32 GetGrpInf(cBgS_PolyInfo&, int) const;
 
diff --git a/include/SSystem/SComponent/c_bg_s_gnd_chk.h b/include/SSystem/SComponent/c_bg_s_gnd_chk.h
index 7a6dca240..23873b4d4 100644
--- a/include/SSystem/SComponent/c_bg_s_gnd_chk.h
+++ b/include/SSystem/SComponent/c_bg_s_gnd_chk.h
@@ -20,11 +20,11 @@ public:
     void SetNowY(f32 y) { mNowY = y; }
     cXyz* GetPointP() { return &m_pos; }
     u32 GetWallPrecheck() const { return mWallPrecheck; }
-    void OffWall() { mFlags &= ~2; }
+    void OffWall() { mFlag &= ~2; }
 
-private:
+public:
     /* 0x24 */ cXyz m_pos;
-    /* 0x30 */ u32 mFlags;
+    /* 0x30 */ u32 mFlag;
     /* 0x34 */ f32 mNowY;
     /* 0x38 */ u32 mWallPrecheck;
     /* 0x3C */ u32 mGndPrecheck;
diff --git a/include/SSystem/SComponent/c_bg_s_lin_chk.h b/include/SSystem/SComponent/c_bg_s_lin_chk.h
index 8efa83a5c..f79757a90 100644
--- a/include/SSystem/SComponent/c_bg_s_lin_chk.h
+++ b/include/SSystem/SComponent/c_bg_s_lin_chk.h
@@ -10,7 +10,7 @@ class cBgS_LinChk : public cBgS_Chk, public cBgS_PolyInfo {
 public:
     /* 0x024 */ cM3dGLin mLin;
     /* 0x040 */ cXyz field_0x40;
-    /* 0x04C */ u32 field_0x4c;
+    /* 0x04C */ u32 mFlag;
     /* 0x050 */ bool mPreWallChk;
     /* 0x051 */ bool mPreGroundChk;
     /* 0x052 */ bool mPreRoofChk;
@@ -26,10 +26,10 @@ public:
 
     virtual ~cBgS_LinChk() {}
 
-    void ClrHit() { field_0x4c &= ~0x10; }
-    void SetHit() { field_0x4c |= 0x10; }
-    u32 ChkHit() const { return field_0x4c & 0x10; }
-    void ClrSttsRoofOff() { field_0x4c &= ~0x20000000; }
+    void ClrHit() { mFlag &= ~0x10; }
+    void SetHit() { mFlag |= 0x10; }
+    u32 ChkHit() const { return mFlag & 0x10; }
+    void ClrSttsRoofOff() { mFlag &= ~0x20000000; }
     void SetCross(const cXyz& pos) { mLin.SetEnd(pos); }
     cXyz& i_GetCross() { return mLin.GetEnd(); }
     cM3dGLin* GetLinP() { return &mLin; }
diff --git a/include/SSystem/SComponent/c_bg_s_poly_info.h b/include/SSystem/SComponent/c_bg_s_poly_info.h
index 45c67dd07..95c94b57c 100644
--- a/include/SSystem/SComponent/c_bg_s_poly_info.h
+++ b/include/SSystem/SComponent/c_bg_s_poly_info.h
@@ -2,6 +2,7 @@
 #define C_BG_S_POLY_INFO_H
 
 #include "dolphin/types.h"
+#include "JSystem/JUtility/JUTAssert.h"
 #include "global.h"
 
 class cBgW;
@@ -25,6 +26,12 @@ public:
     void SetPolyInfo(const cBgS_PolyInfo& other) {
         *this = other;
     }
+    void SetActorInfo(int bg_index, void* bgw, unsigned int actor_id) {
+        JUT_ASSERT(0x59, 0 <= bg_index);
+        mBgIndex = bg_index;
+        mpBgW = (cBgW*)bgw;
+        mActorId = actor_id;
+    }
     bool ChkSafe(const void* bgw, unsigned int pid) {
         if (mpBgW == bgw && mActorId == pid)
             return true;
diff --git a/include/SSystem/SComponent/c_bg_w.h b/include/SSystem/SComponent/c_bg_w.h
index 883c303c7..0ca04eacc 100644
--- a/include/SSystem/SComponent/c_bg_w.h
+++ b/include/SSystem/SComponent/c_bg_w.h
@@ -139,12 +139,12 @@ public:
     bool Set(cBgD_t*, u32, f32(*)[3][4]);
     void RwgLineCheck(u16, cBgS_LinChk*);
     void LineCheckRp(cBgS_LinChk*, int);
-    void LineCheckGrpRp(cBgS_LinChk*, int, int);
+    bool LineCheckGrpRp(cBgS_LinChk*, int, int);
     bool RwgGroundCheckCommon(f32, u16, cBgS_GndChk*);
     bool RwgGroundCheckGnd(u16, cBgS_GndChk*);
     bool RwgGroundCheckWall(u16, cBgS_GndChk*);
     void GroundCrossRp(cBgS_GndChk*, int);
-    void GroundCrossGrpRp(cBgS_GndChk*, int, int);
+    bool GroundCrossGrpRp(cBgS_GndChk*, int, int);
     void CopyOldMtx();
     void Move();
     void RwgShdwDraw(int, cBgS_ShdwDraw*);
diff --git a/src/SSystem/SComponent/c_bg_s.cpp b/src/SSystem/SComponent/c_bg_s.cpp
index 9b8381aae..40a2a6247 100644
--- a/src/SSystem/SComponent/c_bg_s.cpp
+++ b/src/SSystem/SComponent/c_bg_s.cpp
@@ -4,6 +4,8 @@
 //
 
 #include "SSystem/SComponent/c_bg_s.h"
+#include "SSystem/SComponent/c_bg_s_gnd_chk.h"
+#include "SSystem/SComponent/c_bg_s_lin_chk.h"
 #include "SSystem/SComponent/c_bg_w.h"
 #include "JSystem/JUtility/JUTAssert.h"
 #include "dolphin/types.h"
@@ -69,6 +71,10 @@ bool cBgS::Regist(cBgW* bgw, unsigned int pid, void* actor) {
     return true;
 }
 
+static void dummy() {
+    OSReport("c_bg_s_poly_info.h");
+}
+
 /* 80246600-8024669C       .text Release__4cBgSFP4cBgW */
 int cBgS::Release(cBgW* bgw) {
     if (bgw == NULL)
@@ -103,13 +109,42 @@ void cBgS::Dt() {
 }
 
 /* 8024676C-802468E4       .text LineCross__4cBgSFP11cBgS_LinChk */
-bool cBgS::LineCross(cBgS_LinChk*) {
-    /* Nonmatching */
+bool cBgS::LineCross(cBgS_LinChk* chk) {
+    bool ret = false;
+    chk->ClearPi();
+    chk->ClrHit();
+    for (s32 bg_index = 0; bg_index < (s32)ARRAY_SIZE(m_chk_element); bg_index++) {
+        cBgS_ChkElm* elm = &m_chk_element[bg_index];
+        if (elm->ChkUsed() && elm->m_bgw_base_ptr->pm_vtx_tbl != NULL && !chk->ChkSameActorPid(elm->m_actor_id)) {
+            chk->mPreWallChk = !(chk->mFlag & 0x40000000);
+            chk->mPreGroundChk = !(chk->mFlag & 0x80000000);
+            chk->mPreRoofChk = !(chk->mFlag & 0x20000000);
+            if (elm->m_bgw_base_ptr->LineCheckGrpRp(chk, elm->m_bgw_base_ptr->m_rootGrpIdx, 1)) {
+                chk->SetActorInfo(bg_index, elm->m_bgw_base_ptr, elm->m_actor_id);
+                ret = true;
+            }
+        }
+    }
+    if (ret)
+        chk->SetHit();
+    return ret;
 }
 
 /* 802468E4-80246A14       .text GroundCross__4cBgSFP11cBgS_GndChk */
-f32 cBgS::GroundCross(cBgS_GndChk*) {
-    /* Nonmatching */
+f32 cBgS::GroundCross(cBgS_GndChk* chk) {
+    chk->SetNowY(-1e+09);
+    chk->ClearPi();
+    chk->mWallPrecheck = (chk->mFlag & 0x02);
+    chk->mGndPrecheck = (chk->mFlag & 0x01);
+    for (s32 bg_index = 0; bg_index < (s32)ARRAY_SIZE(m_chk_element); bg_index++) {
+        cBgS_ChkElm* elm = &m_chk_element[bg_index];
+        if (elm->ChkUsed() && elm->m_bgw_base_ptr->pm_vtx_tbl != NULL && !chk->ChkSameActorPid(elm->m_actor_id)) {
+            if (elm->m_bgw_base_ptr->GroundCrossGrpRp(chk, elm->m_bgw_base_ptr->m_rootGrpIdx, 1)) {
+                chk->SetActorInfo(bg_index, elm->m_bgw_base_ptr, elm->m_actor_id);
+            }
+        }
+    }
+    return chk->GetNowY();
 }
 
 /* 80246A14-80246C98       .text ConvDzb__4cBgSFPv */
@@ -203,8 +238,13 @@ cM3dGPla* cBgS::GetTriPla(int bg_index, int poly_index) const {
     return m_chk_element[bg_index].m_bgw_base_ptr->GetTriPla(poly_index);
 }
 
+static void dummy2() {
+    // from c_bg_s_poly_info.h
+    OSReport("0 <= grp_index && grp_index < pm_bgd->m_g_num");
+}
+
 /* 802470B8-80247178       .text GetTriPnt__4cBgSCFR13cBgS_PolyInfoP4cXyzP4cXyzP4cXyz */
-bool cBgS::GetTriPnt(cBgS_PolyInfo& poly, cXyz* p0, cXyz* p1, cXyz* p2) const {
+void cBgS::GetTriPnt(cBgS_PolyInfo& poly, cXyz* p0, cXyz* p1, cXyz* p2) const {
     s32 id = poly.GetBgIndex();
     JUT_ASSERT(0x2f6, 0 <= id && id < 256);
     if (m_chk_element[id].ChkUsed())
diff --git a/src/SSystem/SComponent/c_bg_s_gnd_chk.cpp b/src/SSystem/SComponent/c_bg_s_gnd_chk.cpp
index d4b2831cf..31be62c52 100644
--- a/src/SSystem/SComponent/c_bg_s_gnd_chk.cpp
+++ b/src/SSystem/SComponent/c_bg_s_gnd_chk.cpp
@@ -10,5 +10,5 @@
 cBgS_GndChk::cBgS_GndChk() {
     m_pos = cXyz::Zero;
     SetActorPid(0xFFFFFFFF);
-    mFlags = 3;
+    mFlag = 3;
 }
diff --git a/src/SSystem/SComponent/c_bg_s_lin_chk.cpp b/src/SSystem/SComponent/c_bg_s_lin_chk.cpp
index 02e8d6825..f75b5e2b3 100644
--- a/src/SSystem/SComponent/c_bg_s_lin_chk.cpp
+++ b/src/SSystem/SComponent/c_bg_s_lin_chk.cpp
@@ -13,7 +13,7 @@ void cBgS_LinChk::ct() {
     mLin.mEnd = zero;
     field_0x40 = zero;
     SetActorPid(-1);
-    field_0x4c = 0;
+    mFlag = 0;
     mFrontFlag = 1;
     mBackFlag = 0;
 }
diff --git a/src/SSystem/SComponent/c_bg_w.cpp b/src/SSystem/SComponent/c_bg_w.cpp
index 810b3f594..598189c77 100644
--- a/src/SSystem/SComponent/c_bg_w.cpp
+++ b/src/SSystem/SComponent/c_bg_w.cpp
@@ -161,7 +161,7 @@ void cBgW::LineCheckRp(cBgS_LinChk*, int) {
 }
 
 /* 80248868-8024898C       .text LineCheckGrpRp__4cBgWFP11cBgS_LinChkii */
-void cBgW::LineCheckGrpRp(cBgS_LinChk*, int, int) {
+bool cBgW::LineCheckGrpRp(cBgS_LinChk*, int, int) {
     /* Nonmatching */
 }
 
@@ -198,7 +198,7 @@ void cBgW::GroundCrossRp(cBgS_GndChk*, int) {
 }
 
 /* 802491F4-80249368       .text GroundCrossGrpRp__4cBgWFP11cBgS_GndChkii */
-void cBgW::GroundCrossGrpRp(cBgS_GndChk*, int, int) {
+bool cBgW::GroundCrossGrpRp(cBgS_GndChk*, int, int) {
     /* Nonmatching */
 }