diff --git a/src/hardware/hw_clip.c b/src/hardware/hw_clip.c
index a194d3e95..32b41d8a2 100644
--- a/src/hardware/hw_clip.c
+++ b/src/hardware/hw_clip.c
@@ -320,12 +320,12 @@ void gld_clipper_Clear(void)
 
 #define RMUL (1.6f/1.333333f)
 
-angle_t gld_FrustumAngle(void)
+angle_t gld_FrustumAngle(angle_t tiltangle)
 {
 	double floatangle;
 	angle_t a1;
 
-	float tilt = (float)fabs(((double)(int)aimingangle) / ANG1);
+	float tilt = (float)fabs(((double)(int)tiltangle) / ANG1);
 
 	// NEWCLIP TODO: SRB2CBTODO: make a global render_fov for this function
 
@@ -334,12 +334,10 @@ angle_t gld_FrustumAngle(void)
 	float render_multiplier = 64.0f / render_fovratio / RMUL;
 
 	if (tilt > 90.0f)
-	{
 		tilt = 90.0f;
-	}
 
 	// If the pitch is larger than this you can look all around at a FOV of 90
-	if (abs((signed)aimingangle) > 46 * ANG1)
+	if (abs((signed)tiltangle) > 46 * ANG1)
 		return 0xffffffff;
 
 	// ok, this is a gross hack that barely works...
diff --git a/src/hardware/hw_clip.h b/src/hardware/hw_clip.h
index 3ba26e5e5..27a2ed1ef 100644
--- a/src/hardware/hw_clip.h
+++ b/src/hardware/hw_clip.h
@@ -17,7 +17,7 @@
 boolean gld_clipper_SafeCheckRange(angle_t startAngle, angle_t endAngle);
 void gld_clipper_SafeAddClipRange(angle_t startangle, angle_t endangle);
 void gld_clipper_Clear(void);
-angle_t gld_FrustumAngle(void);
+angle_t gld_FrustumAngle(angle_t tiltangle);
 #ifdef HAVE_SPHEREFRUSTRUM
 void gld_FrustrumSetup(void);
 boolean gld_SphereInFrustum(float x, float y, float z, float radius);
diff --git a/src/hardware/hw_defs.h b/src/hardware/hw_defs.h
index 6fea75bee..788661588 100644
--- a/src/hardware/hw_defs.h
+++ b/src/hardware/hw_defs.h
@@ -157,6 +157,7 @@ typedef struct
 #ifdef USE_FTRANSFORM_MIRROR
 	boolean     mirror;          // SRB2Kart: Encore Mode
 #endif
+	boolean     shearing;        // 14042019
 } FTransform;
 
 // Transformed vector, as passed to HWR API
diff --git a/src/hardware/hw_drv.h b/src/hardware/hw_drv.h
index b7f4b4b03..4f4f2b1d1 100644
--- a/src/hardware/hw_drv.h
+++ b/src/hardware/hw_drv.h
@@ -48,7 +48,7 @@ EXPORT void HWRAPI(SetSpecialState) (hwdspecialstate_t IdState, INT32 Value);
 //Hurdler: added for new development
 EXPORT void HWRAPI(DrawModel) (model_t *model, INT32 frameIndex, INT32 duration, INT32 tics, INT32 nextFrameIndex, FTransform *pos, float scale, UINT8 flipped, FSurfaceInfo *Surface);
 EXPORT void HWRAPI(CreateModelVBOs) (model_t *model);
-EXPORT void HWRAPI(SetTransform) (FTransform *ptransform);
+EXPORT void HWRAPI(SetTransform) (FTransform *ptransform, angle_t viewaiming);
 EXPORT INT32 HWRAPI(GetTextureUsed) (void);
 
 EXPORT void HWRAPI(FlushScreenTextures) (void);
diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index 3a688cb5b..5b30df0cf 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -118,6 +118,7 @@ FTransform atransform;
 // Float variants of viewx, viewy, viewz, etc.
 static float gr_viewx, gr_viewy, gr_viewz;
 static float gr_viewsin, gr_viewcos;
+static angle_t gr_aimingangle;
 
 static INT32 drawcount = 0;
 
@@ -3843,9 +3844,10 @@ void HWR_RenderDrawNodes(void)
 		} //i++
 	} // loop++
 
-	HWD.pfnSetTransform(&atransform);
-	HWD.pfnSetShader(0);
 	// Okay! Let's draw it all! Woo!
+	HWD.pfnSetTransform(&atransform, aimingangle);
+	HWD.pfnSetShader(0);
+
 	for (i = 0; i < p; i++)
 	{
 		if (sortnode[sortindex[i]].plane)
@@ -4464,7 +4466,19 @@ static void HWR_RenderFrame(INT32 viewnumber, player_t *player, boolean skybox)
 	atransform.scaley = (float)vid.width/vid.height;
 	atransform.scalez = 1;
 
-	atransform.anglex = (float)(aimingangle>>ANGLETOFINESHIFT)*(360.0f/(float)FINEANGLES);
+	// 14042019
+	if (!cv_grshearing.value)
+	{
+		gr_aimingangle = aimingangle;
+		atransform.shearing = false;
+	}
+	else
+	{
+		gr_aimingangle = 0;
+		atransform.shearing = true;
+	}
+
+	atransform.anglex = (float)(gr_aimingangle>>ANGLETOFINESHIFT)*(360.0f/(float)FINEANGLES);
 	atransform.angley = (float)(viewangle>>ANGLETOFINESHIFT)*(360.0f/(float)FINEANGLES);
 
 	atransform.fovxangle = fpov; // Tails
@@ -4492,7 +4506,7 @@ static void HWR_RenderFrame(INT32 viewnumber, player_t *player, boolean skybox)
 	if (skybox)
 		drewsky = true;
 
-	a1 = gld_FrustumAngle();
+	a1 = gld_FrustumAngle(gr_aimingangle);
 	gld_clipper_Clear();
 	gld_clipper_SafeAddClipRange(viewangle + a1, viewangle - a1);
 #ifdef HAVE_SPHEREFRUSTRUM
@@ -4500,7 +4514,7 @@ static void HWR_RenderFrame(INT32 viewnumber, player_t *player, boolean skybox)
 #endif
 
 	// Set transform and shader
-	HWD.pfnSetTransform(&atransform);
+	HWD.pfnSetTransform(&atransform, aimingangle);
 	HWD.pfnSetShader(0);
 
 	// Check for shaders
@@ -4529,7 +4543,7 @@ static void HWR_RenderFrame(INT32 viewnumber, player_t *player, boolean skybox)
 		HWR_RenderDrawNodes();
 
 	// Unset transform and shader
-	HWD.pfnSetTransform(NULL);
+	HWD.pfnSetTransform(NULL, 0.0f);
 	HWD.pfnUnSetShader();
 
 	// Disable fog
diff --git a/src/hardware/hw_main.h b/src/hardware/hw_main.h
index 6ed5893f7..04f10f123 100644
--- a/src/hardware/hw_main.h
+++ b/src/hardware/hw_main.h
@@ -127,6 +127,7 @@ void HWR_CorrectSWTricks(void);
 
 // Console variables
 extern consvar_t cv_grshaders;
+extern consvar_t cv_grshearing;
 extern consvar_t cv_grfov;
 extern consvar_t cv_grmd2;
 extern consvar_t cv_grfog;
diff --git a/src/hardware/r_opengl/r_opengl.c b/src/hardware/r_opengl/r_opengl.c
index 5866e5716..37c6c74ac 100644
--- a/src/hardware/r_opengl/r_opengl.c
+++ b/src/hardware/r_opengl/r_opengl.c
@@ -185,8 +185,6 @@ FUNCPRINTF void GL_DBG_Printf(const char *format, ...)
 #define pglEnable glEnable
 #define pglDisable glDisable
 #define pglGetFloatv glGetFloatv
-//glGetIntegerv
-//glGetString
 
 /* Depth Buffer */
 #define pglClearDepth glClearDepth
@@ -253,7 +251,6 @@ FUNCPRINTF void GL_DBG_Printf(const char *format, ...)
 /* Miscellaneous */
 typedef void (APIENTRY * PFNglClearColor) (GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha);
 static PFNglClearColor pglClearColor;
-//glClear
 typedef void (APIENTRY * PFNglColorMask) (GLboolean red, GLboolean green, GLboolean blue, GLboolean alpha);
 static PFNglColorMask pglColorMask;
 typedef void (APIENTRY * PFNglAlphaFunc) (GLenum func, GLclampf ref);
@@ -272,8 +269,6 @@ typedef void (APIENTRY * PFNglDisable) (GLenum cap);
 static PFNglDisable pglDisable;
 typedef void (APIENTRY * PFNglGetFloatv) (GLenum pname, GLfloat *params);
 static PFNglGetFloatv pglGetFloatv;
-//glGetIntegerv
-//glGetString
 
 /* Depth Buffer */
 typedef void (APIENTRY * PFNglClearDepth) (GLclampd depth);
@@ -2183,7 +2178,7 @@ EXPORT void HWRAPI(DrawModel) (model_t *model, INT32 frameIndex, INT32 duration,
 // -----------------+
 // SetTransform     :
 // -----------------+
-EXPORT void HWRAPI(SetTransform) (FTransform *stransform)
+EXPORT void HWRAPI(SetTransform) (FTransform *stransform, angle_t viewaiming)
 {
 	static boolean special_splitscreen;
 	pglLoadIdentity();
@@ -2204,12 +2199,27 @@ EXPORT void HWRAPI(SetTransform) (FTransform *stransform)
 		else
 			pglScalef(stransform->scalex, stransform->scaley, -stransform->scalez);
 
+		pglMatrixMode(GL_MODELVIEW);
 		pglRotatef(stransform->anglex, 1.0f, 0.0f, 0.0f);
 		pglRotatef(stransform->angley+270.0f, 0.0f, 1.0f, 0.0f);
 		pglTranslatef(-stransform->x, -stransform->z, -stransform->y);
 
 		pglMatrixMode(GL_PROJECTION);
 		pglLoadIdentity();
+
+		// jimita 14042019
+		// Simulate Software's y-shearing
+		// https://zdoom.org/wiki/Y-shearing
+		if (stransform->shearing)
+		{
+			float tilt = (float)(viewaiming>>ANGLETOFINESHIFT)*(360.0f/(float)FINEANGLES);
+			if (tilt >= 270.0f)
+				tilt = -(90.0f - (tilt - 270.0f));
+			tilt /= 24.0f;		// ?????????
+
+			pglTranslatef(0.0f, -tilt, 0.0f);
+		}
+
 		fovx90 = stransform->fovxangle > 0.0f && fabsf(stransform->fovxangle - 90.0f) < 0.5f;
 		special_splitscreen = (stransform->splitscreen && fovx90);
 		if (special_splitscreen)
diff --git a/src/hardware/r_opengl/r_opengl.h b/src/hardware/r_opengl/r_opengl.h
index d74b9445a..3380bdcbc 100644
--- a/src/hardware/r_opengl/r_opengl.h
+++ b/src/hardware/r_opengl/r_opengl.h
@@ -71,7 +71,6 @@ boolean SetupGLfunc(void);
 void SetupGLFunc4(void);
 void Flush(void);
 INT32 isExtAvailable(const char *extension, const GLubyte *start);
-int SetupPixelFormat(INT32 WantColorBits, INT32 WantStencilBits, INT32 WantDepthBits);
 void SetModelView(GLint w, GLint h);
 void SetStates(void);
 #ifdef USE_PALETTED_TEXTURE
diff --git a/src/r_main.c b/src/r_main.c
index bada24e48..9c143d488 100644
--- a/src/r_main.c
+++ b/src/r_main.c
@@ -1395,6 +1395,7 @@ void R_RegisterEngineStuff(void)
 	CV_RegisterVar(&cv_grsoftwarefog);
 	CV_RegisterVar(&cv_grfogdensity);
 	CV_RegisterVar(&cv_grmd2);
+	CV_RegisterVar(&cv_grshearing);
 	CV_RegisterVar(&cv_grshaders);
 #endif
 
diff --git a/src/v_video.c b/src/v_video.c
index bdebc06b1..b341076c4 100644
--- a/src/v_video.c
+++ b/src/v_video.c
@@ -72,9 +72,9 @@ consvar_t cv_grgammagreen = {"gr_gammagreen", "127", CV_SAVE|CV_CALL, grgamma_co
 consvar_t cv_grgammablue = {"gr_gammablue", "127", CV_SAVE|CV_CALL, grgamma_cons_t,
                             CV_Gammaxxx_ONChange, 0, NULL, NULL, 0, 0, NULL};
 
+consvar_t cv_grshearing = {"gr_shearing", "Off", CV_SAVE, CV_OnOff, NULL, 0, NULL, NULL, 0, 0, NULL};
 
 static CV_PossibleValue_t CV_MD2[] = {{0, "Off"}, {1, "On"}, {2, "Old"}, {0, NULL}};
-// console variables in development
 consvar_t cv_grmd2 = {"gr_md2", "Off", CV_SAVE, CV_MD2, NULL, 0, NULL, NULL, 0, 0, NULL};
 #endif