diff --git a/src/gl/compatibility/gl_20.cpp b/src/gl/compatibility/gl_20.cpp
index c9a615c0c9..de9a957a88 100644
--- a/src/gl/compatibility/gl_20.cpp
+++ b/src/gl/compatibility/gl_20.cpp
@@ -41,7 +41,6 @@
 #include "actorinlines.h"
 #include "g_levellocals.h"
 #include "gl/dynlights/gl_dynlight.h"
-#include "gl/utility/gl_geometric.h"
 #include "gl/renderer/gl_renderer.h"
 #include "gl/renderer/gl_lightdata.h"
 #include "gl/system/gl_interface.h"
@@ -641,7 +640,7 @@ void GLFlat::DrawSubsectorLights(subsector_t * sub, int pass)
 			continue;
 		}
 
-		p.Set(plane.plane);
+		p.Set(plane.plane.Normal(), plane.plane.fD());
 		if (!gl_SetupLight(sub->sector->PortalGroup, p, light, nearPt, up, right, scale, false, pass != GLPASS_LIGHTTEX))
 		{
 			node = node->nextLight;
@@ -715,7 +714,8 @@ bool GLWall::PrepareLight(ADynamicLight * light, int pass)
 	FVector3 nearPt, up, right;
 	float scale;
 
-	p.Set(&glseg);
+	auto normal = glseg.Normal();
+	p.Set(normal, -normal.X * glseg.x1 - normal.Y * glseg.y1);
 
 	if (!p.ValidNormal())
 	{
diff --git a/src/gl/dynlights/gl_dynlight.h b/src/gl/dynlights/gl_dynlight.h
index 1ecdca4ce7..99979f034a 100644
--- a/src/gl/dynlights/gl_dynlight.h
+++ b/src/gl/dynlights/gl_dynlight.h
@@ -25,7 +25,6 @@
 
 #include "c_cvars.h"
 #include "a_dynlight.h"
-#include "gl/utility/gl_geometric.h"
 
 
 struct FDynLightData
diff --git a/src/gl/gl_functions.h b/src/gl/gl_functions.h
index 2401926fff..620533f1e7 100644
--- a/src/gl/gl_functions.h
+++ b/src/gl/gl_functions.h
@@ -7,6 +7,5 @@ class AActor;
 
 void gl_PreprocessLevel();
 void gl_CleanLevelData();
-void gl_LinkLights();
 
 #endif
diff --git a/src/gl/scene/gl_flats.cpp b/src/gl/scene/gl_flats.cpp
index 7413c895ac..b70f6cdfe7 100644
--- a/src/gl/scene/gl_flats.cpp
+++ b/src/gl/scene/gl_flats.cpp
@@ -141,7 +141,7 @@ void GLFlat::SetupSubsectorLights(int pass, subsector_t * sub, int *dli)
 			continue;
 		}
 
-		p.Set(plane.plane);
+		p.Set(plane.plane.Normal(), plane.plane.fD());
 		gl_GetLight(sub->sector->PortalGroup, p, light, false, lightdata);
 		node = node->nextLight;
 	}
diff --git a/src/gl/scene/gl_walls_draw.cpp b/src/gl/scene/gl_walls_draw.cpp
index 17164bc496..1795f17691 100644
--- a/src/gl/scene/gl_walls_draw.cpp
+++ b/src/gl/scene/gl_walls_draw.cpp
@@ -74,14 +74,10 @@ void GLWall::SetupLights()
 	Plane p;
 
 	lightdata.Clear();
-	p.Set(&glseg);
 
-	/*
-	if (!p.ValidNormal()) 
-	{
-		return;
-	}
-	*/
+	auto normal = glseg.Normal();
+	p.Set(normal, -normal.X * glseg.x1 - normal.Y * glseg.y1);
+
 	FLightNode *node;
 	if (seg->sidedef == NULL)
 	{
diff --git a/src/gl/utility/gl_geometric.h b/src/gl/utility/gl_geometric.h
deleted file mode 100644
index 5f5fad8e51..0000000000
--- a/src/gl/utility/gl_geometric.h
+++ /dev/null
@@ -1,86 +0,0 @@
-/*
-** gl_geometric.h
-**
-**---------------------------------------------------------------------------
-** Copyright 2003 Timothy Stump
-** All rights reserved.
-**
-** Redistribution and use in source and binary forms, with or without
-** modification, are permitted provided that the following conditions
-** are met:
-**
-** 1. Redistributions of source code must retain the above copyright
-**    notice, this list of conditions and the following disclaimer.
-** 2. Redistributions in binary form must reproduce the above copyright
-**    notice, this list of conditions and the following disclaimer in the
-**    documentation and/or other materials provided with the distribution.
-** 3. The name of the author may not be used to endorse or promote products
-**    derived from this software without specific prior written permission.
-**
-** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
-** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
-** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
-** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
-** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
-** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-**---------------------------------------------------------------------------
-**
-*/
-
-#ifndef __GL_GEOM
-#define __GL_GEOM
-
-#include "math.h"
-#include "r_defs.h"
-#include "gl/scene/gl_wall.h"
-
-struct GLSeg;
-
-class Plane
-{
-public:
-	void Set(GLSeg *seg)
-	{
-		m_normal = seg->Normal();
-		m_d = m_normal | FVector3(-seg->x1, 0, -seg->y1);
-	}
-
-	void Set(secplane_t &plane)
-	{
-		m_normal = { (float)plane.Normal().X, (float)plane.Normal().Z, (float)plane.Normal().Y };
-		m_d = (float)plane.fD();
-	}
-
-
-	float DistToPoint(float x, float y, float z)
-	{
-		FVector3 p(x, y, z);
-
-		return (m_normal | p) + m_d;
-	}
-
-
-	bool PointOnSide(float x, float y, float z)
-	{
-		return DistToPoint(x, y, z) < 0.f;
-	}
-
-	bool PointOnSide(FVector3 &v) { return PointOnSide(v.X, v.Y, v.Z); }
-	bool ValidNormal() { return m_normal.LengthSquared() == 1.f; }
-
-	float A() { return m_normal.X; }
-	float B() { return m_normal.Y; }
-	float C() { return m_normal.Z; }
-	float D() { return m_d; }
-
-	const FVector3 &Normal() const { return m_normal; }
-protected:
-	FVector3 m_normal;
-	float m_d;
-};
-
-#endif
diff --git a/src/vectors.h b/src/vectors.h
index 95d7c5fdf7..1d5e32307d 100644
--- a/src/vectors.h
+++ b/src/vectors.h
@@ -1673,4 +1673,48 @@ typedef TRotator<double>		DRotator;
 typedef TMatrix3x3<double>		DMatrix3x3;
 typedef TAngle<double>			DAngle;
 
+
+class Plane
+{
+public:
+	void Set(FVector3 normal, float d)
+	{
+		m_normal = normal;
+		m_d = d;
+	}
+
+	// same for a play-vector. Note that y and z are inversed.
+	void Set(DVector3 normal, double d)
+	{
+		m_normal = { (float)normal.X, (float)normal.Z, (float)normal.Y };
+		m_d = (float)d;
+	}
+
+	float DistToPoint(float x, float y, float z)
+	{
+		FVector3 p(x, y, z);
+
+		return (m_normal | p) + m_d;
+	}
+
+
+	bool PointOnSide(float x, float y, float z)
+	{
+		return DistToPoint(x, y, z) < 0.f;
+	}
+
+	bool PointOnSide(FVector3 &v) { return PointOnSide(v.X, v.Y, v.Z); }
+	bool ValidNormal() { return m_normal.LengthSquared() == 1.f; }
+
+	float A() { return m_normal.X; }
+	float B() { return m_normal.Y; }
+	float C() { return m_normal.Z; }
+	float D() { return m_d; }
+
+	const FVector3 &Normal() const { return m_normal; }
+protected:
+	FVector3 m_normal;
+	float m_d;
+};
+
 #endif