diff --git a/src/gl/scene/gl_portal.cpp b/src/gl/scene/gl_portal.cpp
index a186d4ff02..106bf4828f 100644
--- a/src/gl/scene/gl_portal.cpp
+++ b/src/gl/scene/gl_portal.cpp
@@ -952,16 +952,7 @@ void GLMirrorPortal::DrawContents()
 
 int GLMirrorPortal::ClipSeg(seg_t *seg) 
 { 
-	//we cannot use P_PointOnLineSide here because it loses the special meaning of 0 == 'on the line'.
-	int side1 = DMulScale32(seg->v1->y - linedef->v1->y, linedef->dx, linedef->v1->x - seg->v1->x, linedef->dy);
-	int side2 = DMulScale32(seg->v2->y - linedef->v1->y, linedef->dx, linedef->v1->x - seg->v2->x, linedef->dy);
-
-	if (side1 >= 0 && side2 >= 0)
-	// this seg is completely behind the mirror.
-	{
-		return PClip_InFront;
-	}
-	return PClip_Inside; 
+	return P_ClipLineToPortal(seg->linedef, linedef, viewx, viewy) ? PClip_InFront : PClip_Inside;
 }
 
 int GLMirrorPortal::ClipSubsector(subsector_t *sub) 
@@ -994,25 +985,6 @@ int GLMirrorPortal::ClipPoint(fixed_t x, fixed_t y)
 //-----------------------------------------------------------------------------
 //-----------------------------------------------------------------------------
 
-static void glTranslatePortal(line_t* src, line_t* dst, fixed_t& x, fixed_t& y, angle_t & angle)
-{
-	// Get the angle between the two linedefs, for rotating
-	// orientation and velocity. Rotate 180 degrees, and flip
-	// the position across the exit linedef, if reversed.
-
-	double xangle = atan2(double(dst->dy), double(dst->dx)) - atan2(double(src->dy), double(src->dx)) + M_PI;
-	double s = sin(xangle);
-	double c = cos(xangle);
-
-	fixed_t nposx = x - src->v1->x;
-	fixed_t nposy = y - src->v1->y;
-
-	// Rotate position along normal to match exit linedef
-	x = xs_RoundToInt(nposx * c - nposy * s) + dst->v2->x;
-	y = xs_RoundToInt(nposy * c + nposx * s) + dst->v2->y;
-	angle += xs_CRoundToInt(xangle * (ANGLE_180 / M_PI));
-}
-
 void GLLineToLineInfo::init(line_t *line)
 {
 	static const divline_t divlx = { 0, 0, 128 * FRACUNIT, 0 };
@@ -1030,8 +1002,9 @@ void GLLineToLineInfo::init(line_t *line)
 	viewy = ::viewy;
 	viewz = ::viewz;
 	viewangle = ::viewangle;
-	glTranslatePortal(line, line->getPortalDestination(), viewx, viewy, viewangle);
-	P_TranslatePortalZ(line, line->getPortalDestination(), viewz);
+	P_TranslatePortalXY(line, viewx, viewy);
+	P_TranslatePortalAngle(line, viewangle);
+	P_TranslatePortalZ(line, viewz);
 }