diff --git a/src/g_shared/a_skies.cpp b/src/g_shared/a_skies.cpp
index 4e57c638e..57fce23fd 100644
--- a/src/g_shared/a_skies.cpp
+++ b/src/g_shared/a_skies.cpp
@@ -126,13 +126,16 @@ void ASkyPicker::PostBeginPlay ()
 	else
 	{
 		int boxindex = P_GetSkyboxPortal(box);
+		// Do not override special portal types, only regular skies.
 		if (0 == (args[1] & 2))
 		{
-			Sector->Portals[sector_t::ceiling] = boxindex;
+			if (Sector->GetPortalType(sector_t::ceiling) == PORTS_SKYVIEWPOINT)
+				Sector->Portals[sector_t::ceiling] = boxindex;
 		}
 		if (0 == (args[1] & 1))
 		{
-			Sector->Portals[sector_t::floor] = boxindex;
+			if (Sector->GetPortalType(sector_t::floor) == PORTS_SKYVIEWPOINT)
+				Sector->Portals[sector_t::floor] = boxindex;
 		}
 	}
 	Destroy ();
diff --git a/src/gl/compatibility/gl_20.cpp b/src/gl/compatibility/gl_20.cpp
index e059a3563..1dac5ac38 100644
--- a/src/gl/compatibility/gl_20.cpp
+++ b/src/gl/compatibility/gl_20.cpp
@@ -49,6 +49,7 @@
 #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"
 #include "gl/system/gl_cvars.h"
 #include "gl/renderer/gl_renderstate.h"
@@ -452,7 +453,7 @@ bool gl_SetupLight(int group, Plane & p, ADynamicLight * light, Vector & nearPt,
 
 bool gl_SetupLightTexture()
 {
-	if (GLRenderer->gllight == NULL) return false;
+	if (GLRenderer->gllight == nullptr) return false;
 	FMaterial * pat = FMaterial::ValidateTexture(GLRenderer->gllight, false);
 	pat->Bind(CLAMP_XY, 0);
 	return true;
@@ -464,6 +465,95 @@ bool gl_SetupLightTexture()
 //
 //==========================================================================
 
+bool GLWall::PutWallCompat(int passflag)
+{
+	static int list_indices[2][2] =
+	{ { GLLDL_WALLS_PLAIN, GLLDL_WALLS_FOG },{ GLLDL_WALLS_MASKED, GLLDL_WALLS_FOGMASKED } };
+
+	// are lights possible?
+	if (gl_fixedcolormap != CM_DEFAULT || !gl_lights || seg->sidedef == nullptr || type == RENDERWALL_M2SNF || !gltexture) return false;
+
+	// multipassing these is problematic.
+	if ((flags&GLWF_SKYHACK && type == RENDERWALL_M2S)) return false;
+
+	// Any lights affecting this wall?
+	if (!(seg->sidedef->Flags & WALLF_POLYOBJ))
+	{
+		if (seg->sidedef->lighthead == nullptr) return false;
+	}
+	else if (sub)
+	{
+		if (sub->lighthead != nullptr) return false;
+	}
+
+	bool foggy = (!gl_isBlack(Colormap.FadeColor) || level.flags&LEVEL_HASFADETABLE);
+	bool masked = passflag == 2 && gltexture->isMasked();
+
+	int list = list_indices[masked][foggy];
+	if (list == GLLDL_WALLS_PLAIN)
+	{
+		if (gltexture->tex->gl_info.Brightmap && gl.glslversion >= 0.f) list = GLLDL_WALLS_BRIGHT;
+		//if (flags & GLWF_GLOW) list = GLLDL_WALLS_BRIGHT;
+	}
+	gl_drawinfo->dldrawlists[list].AddWall(this);
+	return true;
+
+}
+
+//==========================================================================
+//
+// Fog boundary without any shader support
+//
+//==========================================================================
+
+void GLWall::RenderFogBoundaryCompat()
+{
+	// without shaders some approximation is needed. This won't look as good
+	// as the shader version but it's an acceptable compromise.
+	float fogdensity = gl_GetFogDensity(lightlevel, Colormap.FadeColor);
+
+	float dist1 = Dist2(ViewPos.X, ViewPos.Y, glseg.x1, glseg.y1);
+	float dist2 = Dist2(ViewPos.X, ViewPos.Y, glseg.x2, glseg.y2);
+
+	// these values were determined by trial and error and are scale dependent!
+	float fogd1 = (0.95f - exp(-fogdensity*dist1 / 62500.f)) * 1.05f;
+	float fogd2 = (0.95f - exp(-fogdensity*dist2 / 62500.f)) * 1.05f;
+
+	float fc[4] = { Colormap.FadeColor.r / 255.0f,Colormap.FadeColor.g / 255.0f,Colormap.FadeColor.b / 255.0f,fogd2 };
+
+	gl_RenderState.EnableTexture(false);
+	gl_RenderState.EnableFog(false);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0);
+	gl_RenderState.Apply();
+	glEnable(GL_POLYGON_OFFSET_FILL);
+	glPolygonOffset(-1.0f, -128.0f);
+	glDepthFunc(GL_LEQUAL);
+	glColor4f(fc[0], fc[1], fc[2], fogd1);
+	glBegin(GL_TRIANGLE_FAN);
+	glTexCoord2f(lolft.u, lolft.v);
+	glVertex3f(glseg.x1, zbottom[0], glseg.y1);
+	glTexCoord2f(uplft.u, uplft.v);
+	glVertex3f(glseg.x1, ztop[0], glseg.y1);
+	glColor4f(fc[0], fc[1], fc[2], fogd2);
+	glTexCoord2f(uprgt.u, uprgt.v);
+	glVertex3f(glseg.x2, ztop[1], glseg.y2);
+	glTexCoord2f(lorgt.u, lorgt.v);
+	glVertex3f(glseg.x2, zbottom[1], glseg.y2);
+	glEnd();
+	glDepthFunc(GL_LESS);
+	glPolygonOffset(0.0f, 0.0f);
+	glDisable(GL_POLYGON_OFFSET_FILL);
+	gl_RenderState.EnableFog(true);
+	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.5f);
+	gl_RenderState.EnableTexture(true);
+}
+
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
 void FGLRenderer::RenderMultipassStuff()
 {
 	return;
diff --git a/src/gl/data/gl_vertexbuffer.h b/src/gl/data/gl_vertexbuffer.h
index c56cadcba..b88cc6ca1 100644
--- a/src/gl/data/gl_vertexbuffer.h
+++ b/src/gl/data/gl_vertexbuffer.h
@@ -197,11 +197,12 @@ struct FModelVertex
 class FModelVertexBuffer : public FVertexBuffer
 {
 	int mIndexFrame[2];
-	unsigned int ibo_id;
+	FModelVertex *vbo_ptr;
+	uint32_t ibo_id;
 
 public:
 
-	FModelVertexBuffer(bool needindex);
+	FModelVertexBuffer(bool needindex, bool singleframe);
 	~FModelVertexBuffer();
 
 	FModelVertex *LockVertexBuffer(unsigned int size);
@@ -210,7 +211,7 @@ public:
 	unsigned int *LockIndexBuffer(unsigned int size);
 	void UnlockIndexBuffer();
 
-	unsigned int SetupFrame(unsigned int frame1, unsigned int frame2);
+	unsigned int SetupFrame(unsigned int frame1, unsigned int frame2, unsigned int size);
 	void BindVBO();
 };
 
diff --git a/src/gl/models/gl_models.cpp b/src/gl/models/gl_models.cpp
index dc937ea40..e2187c59c 100644
--- a/src/gl/models/gl_models.cpp
+++ b/src/gl/models/gl_models.cpp
@@ -73,32 +73,17 @@ EXTERN_CVAR(Int, gl_fogmode)
 extern TDeletingArray<FVoxel *> Voxels;
 extern TDeletingArray<FVoxelDef *> VoxelDefs;
 
-
-class DeletingModelArray : public TArray<FModel *>
-{
-public:
-
-#if 1
-	~DeletingModelArray()
-	{
-		for(unsigned i=0;i<Size();i++)
-		{
-			delete (*this)[i];
-		}
-
-	}
-#endif
-};
-
 DeletingModelArray Models;
 
 
 void gl_LoadModels()
 {
+	/*
 	for (int i = Models.Size() - 1; i >= 0; i--)
 	{
 		Models[i]->BuildVertexBuffer();
 	}
+	*/
 }
 
 void gl_FlushModels()
@@ -111,16 +96,22 @@ void gl_FlushModels()
 
 //===========================================================================
 //
+// Uses a hardware buffer if either single frame (i.e. no interpolation needed)
+// or shading is available (interpolation is done by the vertex shader)
 //
+// If interpolation has to be done on the CPU side this will fall back
+// to CPU-side arrays.
 //
 //===========================================================================
 
-FModelVertexBuffer::FModelVertexBuffer(bool needindex)
+FModelVertexBuffer::FModelVertexBuffer(bool needindex, bool singleframe)
+	: FVertexBuffer(singleframe || gl.glslversion > 0)
 {
+	vbo_ptr = nullptr;
 	ibo_id = 0;
 	if (needindex)
 	{
-		glGenBuffers(1, &ibo_id);
+		glGenBuffers(1, &ibo_id);	// The index buffer can always be a real buffer.
 	}
 }
 
@@ -161,6 +152,10 @@ FModelVertexBuffer::~FModelVertexBuffer()
 	{
 		glDeleteBuffers(1, &ibo_id);
 	}
+	if (vbo_ptr != nullptr)
+	{
+		delete[] vbo_ptr;
+	}
 }
 
 //===========================================================================
@@ -171,9 +166,19 @@ FModelVertexBuffer::~FModelVertexBuffer()
 
 FModelVertex *FModelVertexBuffer::LockVertexBuffer(unsigned int size)
 {
-	glBindBuffer(GL_ARRAY_BUFFER, vbo_id);
-	glBufferData(GL_ARRAY_BUFFER, size * sizeof(FModelVertex), NULL, GL_STATIC_DRAW);
-	return (FModelVertex*)glMapBufferRange(GL_ARRAY_BUFFER, 0, size * sizeof(FModelVertex), GL_MAP_WRITE_BIT|GL_MAP_INVALIDATE_BUFFER_BIT);
+	if (vbo_id > 0)
+	{
+		glBindBuffer(GL_ARRAY_BUFFER, vbo_id);
+		glBufferData(GL_ARRAY_BUFFER, size * sizeof(FModelVertex), nullptr, GL_STATIC_DRAW);
+		return (FModelVertex*)glMapBufferRange(GL_ARRAY_BUFFER, 0, size * sizeof(FModelVertex), GL_MAP_WRITE_BIT | GL_MAP_INVALIDATE_BUFFER_BIT);
+	}
+	else
+	{
+		if (vbo_ptr != nullptr) delete[] vbo_ptr;
+		vbo_ptr = new FModelVertex[size];
+		memset(vbo_ptr, 0, size * sizeof(FModelVertex));
+		return vbo_ptr;
+	}
 }
 
 //===========================================================================
@@ -184,8 +189,11 @@ FModelVertex *FModelVertexBuffer::LockVertexBuffer(unsigned int size)
 
 void FModelVertexBuffer::UnlockVertexBuffer()
 {
-	glBindBuffer(GL_ARRAY_BUFFER, vbo_id);
-	glUnmapBuffer(GL_ARRAY_BUFFER); 
+	if (vbo_id > 0)
+	{
+		glBindBuffer(GL_ARRAY_BUFFER, vbo_id);
+		glUnmapBuffer(GL_ARRAY_BUFFER);
+	}
 }
 
 //===========================================================================
@@ -204,7 +212,7 @@ unsigned int *FModelVertexBuffer::LockIndexBuffer(unsigned int size)
 	}
 	else
 	{
-		return NULL;
+		return nullptr;
 	}
 }
 
@@ -216,8 +224,11 @@ unsigned int *FModelVertexBuffer::LockIndexBuffer(unsigned int size)
 
 void FModelVertexBuffer::UnlockIndexBuffer()
 {
-	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo_id);
-	glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER); 
+	if (ibo_id > 0)
+	{
+		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo_id);
+		glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
+	}
 }
 
 
@@ -227,21 +238,44 @@ void FModelVertexBuffer::UnlockIndexBuffer()
 // This must be called after gl_RenderState.Apply!
 //
 //===========================================================================
+static TArray<FModelVertex> iBuffer;
 
-unsigned int FModelVertexBuffer::SetupFrame(unsigned int frame1, unsigned int frame2)
+unsigned int FModelVertexBuffer::SetupFrame(unsigned int frame1, unsigned int frame2, unsigned int size)
 {
 	glBindBuffer(GL_ARRAY_BUFFER, vbo_id);
-	if (gl.glslversion > 0)
+	if (vbo_id > 0)
 	{
-		glVertexAttribPointer(VATTR_VERTEX, 3, GL_FLOAT, false, sizeof(FModelVertex), &VMO[frame1].x);
-		glVertexAttribPointer(VATTR_TEXCOORD, 2, GL_FLOAT, false, sizeof(FModelVertex), &VMO[frame1].u);
-		glVertexAttribPointer(VATTR_VERTEX2, 3, GL_FLOAT, false, sizeof(FModelVertex), &VMO[frame2].x);
+		if (gl.glslversion > 0)
+		{
+			glVertexAttribPointer(VATTR_VERTEX, 3, GL_FLOAT, false, sizeof(FModelVertex), &VMO[frame1].x);
+			glVertexAttribPointer(VATTR_TEXCOORD, 2, GL_FLOAT, false, sizeof(FModelVertex), &VMO[frame1].u);
+			glVertexAttribPointer(VATTR_VERTEX2, 3, GL_FLOAT, false, sizeof(FModelVertex), &VMO[frame2].x);
+		}
+		else
+		{
+			// only used for single frame models so there is no vertex2 here, which has no use without a shader.
+			glVertexPointer(3, GL_FLOAT, sizeof(FModelVertex), &VMO[frame1].x);
+			glTexCoordPointer(2, GL_FLOAT, sizeof(FModelVertex), &VMO[frame1].u);
+		}
+	}
+	else if (frame1 == frame2 || size == 0 || gl_RenderState.GetInterpolationFactor() == 0.f)
+	{
+		glVertexPointer(3, GL_FLOAT, sizeof(FModelVertex), &vbo_ptr[frame1].x);
+		glTexCoordPointer(2, GL_FLOAT, sizeof(FModelVertex), &vbo_ptr[frame1].u);
 	}
 	else
 	{
-		// only used for single frame models so there is no vertex2 here, which has no use without a shader.
-		glVertexPointer(3, GL_FLOAT, sizeof(FModelVertex), &VMO[frame1].x);
-		glTexCoordPointer(2, GL_FLOAT, sizeof(FModelVertex), &VMO[frame1].u);
+		// must interpolate
+		iBuffer.Resize(size);
+		glVertexPointer(3, GL_FLOAT, sizeof(FModelVertex), &iBuffer[0].x);
+		glTexCoordPointer(2, GL_FLOAT, sizeof(FModelVertex), &vbo_ptr[frame1].u);
+		float frac = gl_RenderState.GetInterpolationFactor();
+		for (unsigned i = 0; i < size; i++)
+		{
+			iBuffer[i].x = vbo_ptr[frame1 + i].x * (1.f - frac) + vbo_ptr[frame2 + i].x * frac;
+			iBuffer[i].y = vbo_ptr[frame1 + i].y * (1.f - frac) + vbo_ptr[frame2 + i].y * frac;
+			iBuffer[i].z = vbo_ptr[frame1 + i].z * (1.f - frac) + vbo_ptr[frame2 + i].z * frac;
+		}
 	}
 	return frame1;
 }
@@ -254,7 +288,7 @@ unsigned int FModelVertexBuffer::SetupFrame(unsigned int frame1, unsigned int fr
 
 FModel::~FModel()
 {
-	if (mVBuf != NULL) delete mVBuf;
+	if (mVBuf != nullptr) delete mVBuf;
 }
 
 
@@ -266,8 +300,8 @@ static int * SpriteModelHash;
 
 static void DeleteModelHash()
 {
-	if (SpriteModelHash != NULL) delete [] SpriteModelHash;
-	SpriteModelHash = NULL;
+	if (SpriteModelHash != nullptr) delete [] SpriteModelHash;
+	SpriteModelHash = nullptr;
 }
 
 //===========================================================================
@@ -278,12 +312,15 @@ static void DeleteModelHash()
 
 static int FindGFXFile(FString & fn)
 {
+	int lump = Wads.CheckNumForFullName(fn);	// if we find something that matches the name plus the extension, return it and do not enter the substitution logic below.
+	if (lump != -1) return lump;
+
 	int best = -1;
 	int dot = fn.LastIndexOf('.');
 	int slash = fn.LastIndexOf('/');
 	if (dot > slash) fn.Truncate(dot);
 
-	static const char * extensions[] = { ".png", ".jpg", ".tga", ".pcx", NULL };
+	static const char * extensions[] = { ".png", ".jpg", ".tga", ".pcx", nullptr };
 
 	for (const char ** extp=extensions; *extp; extp++)
 	{
@@ -300,7 +337,7 @@ static int FindGFXFile(FString & fn)
 //
 //===========================================================================
 
-FTexture * LoadSkin(const char * path, const char * fn)
+FTextureID LoadSkin(const char * path, const char * fn)
 {
 	FString buffer;
 
@@ -309,11 +346,11 @@ FTexture * LoadSkin(const char * path, const char * fn)
 	int texlump = FindGFXFile(buffer);
 	if (texlump>=0)
 	{
-		return TexMan.FindTexture(Wads.GetLumpFullName(texlump), FTexture::TEX_Any, FTextureManager::TEXMAN_TryAny);
+		return TexMan.CheckForTexture(Wads.GetLumpFullName(texlump), FTexture::TEX_Any, FTextureManager::TEXMAN_TryAny);
 	}
 	else 
 	{
-		return NULL;
+		return FNullTextureID();
 	}
 }
 
@@ -344,9 +381,9 @@ static int ModelFrameHash(FSpriteModelFrame * smf)
 //
 //===========================================================================
 
-static FModel * FindModel(const char * path, const char * modelfile)
+static unsigned FindModel(const char * path, const char * modelfile)
 {
-	FModel * model = NULL;
+	FModel * model = nullptr;
 	FString fullname;
 
 	fullname.Format("%s%s", path, modelfile);
@@ -355,12 +392,12 @@ static FModel * FindModel(const char * path, const char * modelfile)
 	if (lump<0)
 	{
 		Printf("FindModel: '%s' not found\n", fullname.GetChars());
-		return NULL;
+		return -1;
 	}
 
-	for(int i = 0; i< (int)Models.Size(); i++)
+	for(unsigned i = 0; i< Models.Size(); i++)
 	{
-		if (!Models[i]->mFileName.CompareNoCase(fullname)) return Models[i];
+		if (!Models[i]->mFileName.CompareNoCase(fullname)) return i;
 	}
 
 	int len = Wads.LumpLength(lump);
@@ -380,32 +417,31 @@ static FModel * FindModel(const char * path, const char * modelfile)
 		model = new FMD3Model;
 	}
 
-	if (model != NULL)
+	if (model != nullptr)
 	{
 		if (!model->Load(path, lump, buffer, len))
 		{
 			delete model;
-			return NULL;
+			return -1;
 		}
 	}
 	else
 	{
 		// try loading as a voxel
 		FVoxel *voxel = R_LoadKVX(lump);
-		if (voxel != NULL)
+		if (voxel != nullptr)
 		{
 			model = new FVoxelModel(voxel, true);
 		}
 		else
 		{
 			Printf("LoadModel: Unknown model format in '%s'\n", fullname.GetChars());
-			return NULL;
+			return -1;
 		}
 	}
 	// The vertex buffer cannot be initialized here because this gets called before OpenGL is initialized
 	model->mFileName = fullname;
-	Models.Push(model);
-	return model;
+	return Models.Push(model);
 }
 
 //===========================================================================
@@ -444,8 +480,9 @@ void gl_InitModels()
 	{
 		FVoxelModel *md = (FVoxelModel*)Models[VoxelDefs[i]->Voxel->VoxelIndex];
 		memset(&smf, 0, sizeof(smf));
-		smf.models[0] = md;
-		smf.skins[0] = md->GetPaletteTexture();
+		smf.modelIDs[1] = smf.modelIDs[2] = smf.modelIDs[3] = -1;
+		smf.modelIDs[0] = VoxelDefs[i]->Voxel->VoxelIndex;
+		smf.skinIDs[0] = md->GetPaletteTexture();
 		smf.xscale = smf.yscale = smf.zscale = VoxelDefs[i]->Scale;
 		smf.angleoffset = VoxelDefs[i]->AngleOffset.Degrees;
 		if (VoxelDefs[i]->PlacedSpin != 0)
@@ -474,6 +511,7 @@ void gl_InitModels()
 	}
 
 	memset(&smf, 0, sizeof(smf));
+	smf.modelIDs[0] = smf.modelIDs[1] = smf.modelIDs[2] = smf.modelIDs[3] = -1;
 	while ((Lump = Wads.FindLump("MODELDEF", &lastLump)) != -1)
 	{
 		FScanner sc(Lump);
@@ -483,10 +521,11 @@ void gl_InitModels()
 			{
 				sc.MustGetString();
 				memset(&smf, 0, sizeof(smf));
+				smf.modelIDs[1] = smf.modelIDs[2] = smf.modelIDs[3] = -1;
 				smf.xscale=smf.yscale=smf.zscale=1.f;
 
 				smf.type = PClass::FindClass(sc.String);
-				if (!smf.type || smf.type->Defaults == NULL) 
+				if (!smf.type || smf.type->Defaults == nullptr) 
 				{
 					sc.ScriptError("MODELDEF: Unknown actor type '%s'\n", sc.String);
 				}
@@ -505,15 +544,15 @@ void gl_InitModels()
 					else if (sc.Compare("model"))
 					{
 						sc.MustGetNumber();
-						index=sc.Number;
-						if (index<0 || index>=MAX_MODELS_PER_FRAME)
+						index = sc.Number;
+						if (index < 0 || index >= MAX_MODELS_PER_FRAME)
 						{
 							sc.ScriptError("Too many models in %s", smf.type->TypeName.GetChars());
 						}
 						sc.MustGetString();
 						FixPathSeperator(sc.String);
-						smf.models[index] = FindModel(path.GetChars(), sc.String);
-						if (!smf.models[index])
+						smf.modelIDs[index] = FindModel(path.GetChars(), sc.String);
+						if (smf.modelIDs[index] == -1)
 						{
 							Printf("%s: model not found in %s\n", sc.String, path.GetChars());
 						}
@@ -521,11 +560,11 @@ void gl_InitModels()
 					else if (sc.Compare("scale"))
 					{
 						sc.MustGetFloat();
-						smf.xscale=sc.Float;
+						smf.xscale = sc.Float;
 						sc.MustGetFloat();
-						smf.yscale=sc.Float;
+						smf.yscale = sc.Float;
 						sc.MustGetFloat();
-						smf.zscale=sc.Float;
+						smf.zscale = sc.Float;
 					}
 					// [BB] Added zoffset reading. 
 					// Now it must be considered deprecated.
@@ -631,12 +670,12 @@ void gl_InitModels()
 						FixPathSeperator(sc.String);
 						if (sc.Compare(""))
 						{
-							smf.skins[index]=NULL;
+							smf.skinIDs[index]=FNullTextureID();
 						}
 						else
 						{
-							smf.skins[index]=LoadSkin(path.GetChars(), sc.String);
-							if (smf.skins[index] == NULL)
+							smf.skinIDs[index] = LoadSkin(path.GetChars(), sc.String);
+							if (!smf.skinIDs[index].isValid())
 							{
 								Printf("Skin '%s' not found in '%s'\n",
 									sc.String, smf.type->TypeName.GetChars());
@@ -678,9 +717,10 @@ void gl_InitModels()
 						if (isframe)
 						{
 							sc.MustGetString();
-							if (smf.models[index]!=NULL) 
+							if (smf.modelIDs[index] != -1)
 							{
-								smf.modelframes[index] = smf.models[index]->FindFrame(sc.String);
+								FModel *model = Models[smf.modelIDs[index]];
+								smf.modelframes[index] = model->FindFrame(sc.String);
 								if (smf.modelframes[index]==-1) sc.ScriptError("Unknown frame '%s' in %s", sc.String, smf.type->TypeName.GetChars());
 							}
 							else smf.modelframes[index] = -1;
@@ -765,7 +805,7 @@ FSpriteModelFrame * gl_FindModelFrame(const PClass * ti, int sprite, int frame,
 		if (frame < sprdef->numframes)
 		{
 			spriteframe_t *sprframe = &SpriteFrames[sprdef->spriteframes + frame];
-			if (sprframe->Voxel != NULL)
+			if (sprframe->Voxel != nullptr)
 			{
 				int index = sprframe->Voxel->VoxeldefIndex;
 				if (dropped && sprframe->Voxel->DroppedSpin !=sprframe->Voxel->PlacedSpin) index++;
@@ -773,7 +813,7 @@ FSpriteModelFrame * gl_FindModelFrame(const PClass * ti, int sprite, int frame,
 			}
 		}
 	}
-	return NULL;
+	return nullptr;
 }
 
 
@@ -792,7 +832,7 @@ void gl_RenderFrameModels( const FSpriteModelFrame *smf,
 {
 	// [BB] Frame interpolation: Find the FSpriteModelFrame smfNext which follows after smf in the animation
 	// and the scalar value inter ( element of [0,1) ), both necessary to determine the interpolated frame.
-	FSpriteModelFrame * smfNext = NULL;
+	FSpriteModelFrame * smfNext = nullptr;
 	double inter = 0.;
 	if( gl_interpolate_model_frames && !(smf->flags & MDL_NOINTERPOLATION) )
 	{
@@ -839,17 +879,17 @@ void gl_RenderFrameModels( const FSpriteModelFrame *smf,
 
 	for(int i=0; i<MAX_MODELS_PER_FRAME; i++)
 	{
-		FModel * mdl = smf->models[i];
-
-		if (mdl!=NULL)
+		if (smf->modelIDs[i] != -1)
 		{
+			FModel * mdl = Models[smf->modelIDs[i]];
+			FTexture *tex = smf->skinIDs[i].isValid()? TexMan(smf->skinIDs[i]) : nullptr;
 			mdl->BuildVertexBuffer();
 			gl_RenderState.SetVertexBuffer(mdl->mVBuf);
 
 			if ( smfNext && smf->modelframes[i] != smfNext->modelframes[i] )
-				mdl->RenderFrame(smf->skins[i], smf->modelframes[i], smfNext->modelframes[i], inter, translation);
+				mdl->RenderFrame(tex, smf->modelframes[i], smfNext->modelframes[i], inter, translation);
 			else
-				mdl->RenderFrame(smf->skins[i], smf->modelframes[i], smf->modelframes[i], 0.f, translation);
+				mdl->RenderFrame(tex, smf->modelframes[i], smf->modelframes[i], 0.f, translation);
 
 			gl_RenderState.SetVertexBuffer(GLRenderer->mVBO);
 		}
@@ -949,12 +989,12 @@ void gl_RenderModel(GLSprite * spr)
 	gl_RenderState.mModelMatrix.rotate(-smf->rolloffset, 1, 0, 0);
 
 	// consider the pixel stretching. For non-voxels this must be factored out here
-	float stretch = (smf->models[0] != NULL ? smf->models[0]->getAspectFactor() : 1.f) / glset.pixelstretch;
+	float stretch = (smf->modelIDs[0] != -1 ? Models[smf->modelIDs[0]]->getAspectFactor() : 1.f) / glset.pixelstretch;
 	gl_RenderState.mModelMatrix.scale(1, stretch, 1);
 
 
 	gl_RenderState.EnableModelMatrix(true);
-	gl_RenderFrameModels( smf, spr->actor->state, spr->actor->tics, spr->actor->GetClass(), NULL, translation );
+	gl_RenderFrameModels( smf, spr->actor->state, spr->actor->tics, spr->actor->GetClass(), nullptr, translation );
 	gl_RenderState.EnableModelMatrix(false);
 
 	glDepthFunc(GL_LESS);
@@ -975,7 +1015,7 @@ void gl_RenderHUDModel(pspdef_t *psp, float ofsX, float ofsY)
 	FSpriteModelFrame *smf = gl_FindModelFrame(playermo->player->ReadyWeapon->GetClass(), psp->state->sprite, psp->state->GetFrame(), false);
 
 	// [BB] No model found for this sprite, so we can't render anything.
-	if ( smf == NULL )
+	if ( smf == nullptr )
 		return;
 
 	glDepthFunc(GL_LEQUAL);
@@ -1012,7 +1052,7 @@ void gl_RenderHUDModel(pspdef_t *psp, float ofsX, float ofsY)
 	gl_RenderState.mViewMatrix.rotate(-smf->rolloffset, 1, 0, 0);
 	gl_RenderState.ApplyMatrices();
 
-	gl_RenderFrameModels( smf, psp->state, psp->tics, playermo->player->ReadyWeapon->GetClass(), NULL, 0 );
+	gl_RenderFrameModels( smf, psp->state, psp->tics, playermo->player->ReadyWeapon->GetClass(), nullptr, 0 );
 
 	glDepthFunc(GL_LESS);
 	if (!( playermo->RenderStyle == LegacyRenderStyles[STYLE_Normal] ))
@@ -1027,11 +1067,11 @@ void gl_RenderHUDModel(pspdef_t *psp, float ofsX, float ofsY)
 
 bool gl_IsHUDModelForPlayerAvailable (player_t * player)
 {
-	if ( (player == NULL) || (player->ReadyWeapon == NULL) || (player->psprites[0].state == NULL) )
+	if ( (player == nullptr) || (player->ReadyWeapon == nullptr) || (player->psprites[0].state == nullptr) )
 		return false;
 
 	FState* state = player->psprites[0].state;
 	FSpriteModelFrame *smf = gl_FindModelFrame(player->ReadyWeapon->GetClass(), state->sprite, state->GetFrame(), false);
-	return ( smf != NULL );
+	return ( smf != nullptr );
 }
 
diff --git a/src/gl/models/gl_models.h b/src/gl/models/gl_models.h
index a99f81322..33fa00736 100644
--- a/src/gl/models/gl_models.h
+++ b/src/gl/models/gl_models.h
@@ -1,6 +1,7 @@
 #ifndef __GL_MODELS_H_
 #define __GL_MODELS_H_
 
+#include "tarray.h"
 #include "gl/utility/gl_geometric.h"
 #include "gl/data/gl_vertexbuffer.h"
 #include "p_pspr.h"
@@ -16,7 +17,7 @@ enum { VX, VZ, VY };
 #define MD3_MAGIC			0x33504449
 #define NUMVERTEXNORMALS	162
 
-FTexture * LoadSkin(const char * path, const char * fn);
+FTextureID LoadSkin(const char * path, const char * fn);
 
 
 class FModel
@@ -33,6 +34,7 @@ public:
 	virtual int FindFrame(const char * name) = 0;
 	virtual void RenderFrame(FTexture * skin, int frame, int frame2, double inter, int translation=0) = 0;
 	virtual void BuildVertexBuffer() = 0;
+	virtual void AddSkins(BYTE *hitlist) = 0;
 	void DestroyVertexBuffer()
 	{
 		delete mVBuf;
@@ -124,7 +126,7 @@ protected:
 	int				mLumpNum;
 	DMDHeader	    header;
 	DMDInfo			info;
-	FTexture **		skins;
+	FTextureID *	skins;
 	ModelFrame  *	frames;
 	bool			allowTexComp;  // Allow texture compression with this.
 
@@ -154,6 +156,8 @@ public:
 	virtual int FindFrame(const char * name);
 	virtual void RenderFrame(FTexture * skin, int frame, int frame2, double inter, int translation=0);
 	virtual void LoadGeometry();
+	virtual void AddSkins(BYTE *hitlist);
+
 	void UnloadGeometry();
 	void BuildVertexBuffer();
 
@@ -201,7 +205,7 @@ class FMD3Model : public FModel
 		int numTriangles;
 		int numSkins;
 
-		FTexture ** skins;
+		FTextureID * skins;
 		MD3Triangle * tris;
 		MD3TexCoord * texcoords;
 		MD3Vertex * vertices;
@@ -259,6 +263,7 @@ public:
 	virtual void RenderFrame(FTexture * skin, int frame, int frame2, double inter, int translation=0);
 	void LoadGeometry();
 	void BuildVertexBuffer();
+	virtual void AddSkins(BYTE *hitlist);
 };
 
 struct FVoxelVertexHash
@@ -295,7 +300,7 @@ class FVoxelModel : public FModel
 protected:
 	FVoxel *mVoxel;
 	bool mOwningVoxel;	// if created through MODELDEF deleting this object must also delete the voxel object
-	FTexture *mPalette;
+	FTextureID mPalette;
 	unsigned int mNumIndices;
 	TArray<FModelVertex> mVertices;
 	TArray<unsigned int> mIndices;
@@ -311,7 +316,8 @@ public:
 	void Initialize();
 	virtual int FindFrame(const char * name);
 	virtual void RenderFrame(FTexture * skin, int frame, int frame2, double inter, int translation=0);
-	FTexture *GetPaletteTexture() const { return mPalette; }
+	virtual void AddSkins(BYTE *hitlist);
+	FTextureID GetPaletteTexture() const { return mPalette; }
 	void BuildVertexBuffer();
 	float getAspectFactor();
 };
@@ -338,8 +344,8 @@ enum
 
 struct FSpriteModelFrame
 {
-	FModel * models[MAX_MODELS_PER_FRAME];
-	FTexture * skins[MAX_MODELS_PER_FRAME];
+	int modelIDs[MAX_MODELS_PER_FRAME];
+	FTextureID skinIDs[MAX_MODELS_PER_FRAME];
 	int modelframes[MAX_MODELS_PER_FRAME];
 	float xscale, yscale, zscale;
 	// [BB] Added zoffset, rotation parameters and flags.
@@ -368,4 +374,21 @@ void gl_RenderModel(GLSprite * spr);
 void gl_RenderHUDModel(pspdef_t *psp, float ofsx, float ofsy);
 bool gl_IsHUDModelForPlayerAvailable (player_t * player);
 
+
+class DeletingModelArray : public TArray<FModel *>
+{
+public:
+
+	~DeletingModelArray()
+	{
+		for (unsigned i = 0; i<Size(); i++)
+		{
+			delete (*this)[i];
+		}
+
+	}
+};
+
+extern DeletingModelArray Models;
+
 #endif
diff --git a/src/gl/models/gl_models_md2.cpp b/src/gl/models/gl_models_md2.cpp
index 7a27e12dc..c0bd155fb 100644
--- a/src/gl/models/gl_models_md2.cpp
+++ b/src/gl/models/gl_models_md2.cpp
@@ -159,7 +159,7 @@ bool FDMDModel::Load(const char * path, int lumpnum, const char * buffer, int le
 	}
 
 	// Allocate and load in the data.
-	skins = new FTexture *[info.numSkins];
+	skins = new FTextureID[info.numSkins];
 
 	for (i = 0; i < info.numSkins; i++)
 	{
@@ -304,7 +304,7 @@ void FDMDModel::BuildVertexBuffer()
 		int VertexBufferSize = info.numFrames * lodInfo[0].numTriangles * 3;
 		unsigned int vindex = 0;
 
-		mVBuf = new FModelVertexBuffer(false);
+		mVBuf = new FModelVertexBuffer(false, info.numFrames == 1);
 		FModelVertex *vertptr = mVBuf->LockVertexBuffer(VertexBufferSize);
 
 		for (int i = 0; i < info.numFrames; i++)
@@ -336,7 +336,22 @@ void FDMDModel::BuildVertexBuffer()
 	}
 }
 
+//===========================================================================
+//
+// for skin precaching
+//
+//===========================================================================
 
+void FDMDModel::AddSkins(BYTE *hitlist)
+{
+	for (int i = 0; i < info.numSkins; i++)
+	{
+		if (skins[i].isValid())
+		{
+			hitlist[skins[i].GetIndex()] |= FTexture::TEX_Flat;
+		}
+	}
+}
 
 //===========================================================================
 //
@@ -364,8 +379,8 @@ void FDMDModel::RenderFrame(FTexture * skin, int frameno, int frameno2, double i
 
 	if (!skin)
 	{
-		if (info.numSkins == 0) return;
-		skin = skins[0];
+		if (info.numSkins == 0 || !skins[0].isValid()) return;
+		skin = TexMan(skins[0]);
 		if (!skin) return;
 	}
 
@@ -375,7 +390,7 @@ void FDMDModel::RenderFrame(FTexture * skin, int frameno, int frameno2, double i
 	gl_RenderState.SetInterpolationFactor((float)inter);
 
 	gl_RenderState.Apply();
-	mVBuf->SetupFrame(frames[frameno].vindex, frames[frameno2].vindex);
+	mVBuf->SetupFrame(frames[frameno].vindex, frames[frameno2].vindex, lodInfo[0].numTriangles * 3);
 	glDrawArrays(GL_TRIANGLES, 0, lodInfo[0].numTriangles * 3);
 	gl_RenderState.SetInterpolationFactor(0.f);
 }
@@ -469,7 +484,7 @@ bool FMD2Model::Load(const char * path, int lumpnum, const char * buffer, int le
 		return false;
 	}
 
-	skins = new FTexture *[info.numSkins];
+	skins = new FTextureID[info.numSkins];
 
 	for (i = 0; i < info.numSkins; i++)
 	{
diff --git a/src/gl/models/gl_models_md3.cpp b/src/gl/models/gl_models_md3.cpp
index 024f8ac81..267e85c91 100644
--- a/src/gl/models/gl_models_md3.cpp
+++ b/src/gl/models/gl_models_md3.cpp
@@ -179,14 +179,14 @@ bool FMD3Model::Load(const char * path, int lumpnum, const char * buffer, int le
 
 		// copy shaders (skins)
 		md3_shader_t * shader = (md3_shader_t*)(((char*)ss) + LittleLong(ss->Ofs_Shaders));
-		s->skins = new FTexture *[s->numSkins];
+		s->skins = new FTextureID[s->numSkins];
 
 		for (int i = 0; i < s->numSkins; i++)
 		{
 			// [BB] According to the MD3 spec, Name is supposed to include the full path.
 			s->skins[i] = LoadSkin("", shader[i].Name);
 			// [BB] Fall back and check if Name is relative.
-			if (s->skins[i] == NULL)
+			if (!s->skins[i].isValid())
 				s->skins[i] = LoadSkin(path, shader[i].Name);
 		}
 	}
@@ -255,7 +255,7 @@ void FMD3Model::LoadGeometry()
 
 void FMD3Model::BuildVertexBuffer()
 {
-	if (mVBuf == NULL)
+	if (mVBuf == nullptr)
 	{
 		LoadGeometry();
 
@@ -269,11 +269,11 @@ void FMD3Model::BuildVertexBuffer()
 			ibufsize += 3 * surf->numTriangles;
 		}
 
-		mVBuf = new FModelVertexBuffer(true);
+		mVBuf = new FModelVertexBuffer(true, numFrames == 1);
 		FModelVertex *vertptr = mVBuf->LockVertexBuffer(vbufsize);
 		unsigned int *indxptr = mVBuf->LockIndexBuffer(ibufsize);
 
-		assert(vertptr != NULL && indxptr != NULL);
+		assert(vertptr != nullptr && indxptr != nullptr);
 
 		unsigned int vindex = 0, iindex = 0;
 
@@ -309,6 +309,27 @@ void FMD3Model::BuildVertexBuffer()
 }
 
 
+//===========================================================================
+//
+// for skin precaching
+//
+//===========================================================================
+
+void FMD3Model::AddSkins(BYTE *hitlist)
+{
+	for (int i = 0; i < numSurfaces; i++)
+	{
+		MD3Surface * surf = &surfaces[i];
+		for (int j = 0; j < surf->numSkins; j++)
+		{
+			if (surf->skins[j].isValid())
+			{
+				hitlist[surf->skins[j].GetIndex()] |= FTexture::TEX_Flat;
+			}
+		}
+	}
+}
+
 //===========================================================================
 //
 //
@@ -344,8 +365,8 @@ void FMD3Model::RenderFrame(FTexture * skin, int frameno, int frameno2, double i
 		FTexture *surfaceSkin = skin;
 		if (!surfaceSkin)
 		{
-			if (surf->numSkins==0) return;
-			surfaceSkin = surf->skins[0];
+			if (surf->numSkins==0 || !surf->skins[0].isValid()) return;
+			surfaceSkin = TexMan(surf->skins[0]);
 			if (!surfaceSkin) return;
 		}
 
@@ -354,7 +375,7 @@ void FMD3Model::RenderFrame(FTexture * skin, int frameno, int frameno2, double i
 		gl_RenderState.SetMaterial(tex, CLAMP_NONE, translation, -1, false);
 
 		gl_RenderState.Apply();
-		mVBuf->SetupFrame(surf->vindex + frameno * surf->numVertices, surf->vindex + frameno2 * surf->numVertices);
+		mVBuf->SetupFrame(surf->vindex + frameno * surf->numVertices, surf->vindex + frameno2 * surf->numVertices, surf->numVertices);
 		glDrawElements(GL_TRIANGLES, surf->numTriangles * 3, GL_UNSIGNED_INT, (void*)(intptr_t)(surf->iindex * sizeof(unsigned int)));
 	}
 	gl_RenderState.SetInterpolationFactor(0.f);
@@ -370,6 +391,6 @@ FMD3Model::~FMD3Model()
 {
 	if (frames) delete [] frames;
 	if (surfaces) delete [] surfaces;
-	frames = NULL;
-	surfaces = NULL;
+	frames = nullptr;
+	surfaces = nullptr;
 }
diff --git a/src/gl/models/gl_voxels.cpp b/src/gl/models/gl_voxels.cpp
index 3a34117b9..ec7f0573b 100644
--- a/src/gl/models/gl_voxels.cpp
+++ b/src/gl/models/gl_voxels.cpp
@@ -213,7 +213,7 @@ FVoxelModel::FVoxelModel(FVoxel *voxel, bool owned)
 {
 	mVoxel = voxel;
 	mOwningVoxel = owned;
-	mPalette = new FVoxelTexture(voxel);
+	mPalette = TexMan.AddTexture(new FVoxelTexture(voxel));
 }
 
 //===========================================================================
@@ -224,7 +224,6 @@ FVoxelModel::FVoxelModel(FVoxel *voxel, bool owned)
 
 FVoxelModel::~FVoxelModel()
 {
-	delete mPalette;
 	if (mOwningVoxel) delete mVoxel;
 }
 
@@ -378,7 +377,7 @@ void FVoxelModel::BuildVertexBuffer()
 	{
 		Initialize();
 
-		mVBuf = new FModelVertexBuffer(true);
+		mVBuf = new FModelVertexBuffer(true, true);
 		FModelVertex *vertptr = mVBuf->LockVertexBuffer(mVertices.Size());
 		unsigned int *indxptr = mVBuf->LockIndexBuffer(mIndices.Size());
 
@@ -398,6 +397,17 @@ void FVoxelModel::BuildVertexBuffer()
 }
 
 
+//===========================================================================
+//
+// for skin precaching
+//
+//===========================================================================
+
+void FVoxelModel::AddSkins(BYTE *hitlist)
+{
+	hitlist[mPalette.GetIndex()] |= FTexture::TEX_Flat;
+}
+
 //===========================================================================
 //
 // 
@@ -443,7 +453,7 @@ void FVoxelModel::RenderFrame(FTexture * skin, int frame, int frame2, double int
 	gl_RenderState.SetMaterial(tex, CLAMP_NOFILTER, translation, -1, false);
 
 	gl_RenderState.Apply();
-	mVBuf->SetupFrame(0, 0);
+	mVBuf->SetupFrame(0, 0, 0);
 	glDrawElements(GL_TRIANGLES, mNumIndices, GL_UNSIGNED_INT, (void*)(intptr_t)0);
 }
 
diff --git a/src/gl/renderer/gl_renderstate.h b/src/gl/renderer/gl_renderstate.h
index cebbb9570..0172488eb 100644
--- a/src/gl/renderer/gl_renderstate.h
+++ b/src/gl/renderer/gl_renderstate.h
@@ -439,6 +439,11 @@ public:
 		mInterpolationFactor = fac;
 	}
 
+	float GetInterpolationFactor()
+	{
+		return mInterpolationFactor;
+	}
+
 	// Backwards compatibility crap follows
 	void ApplyFixedFunction();
 	void DrawColormapOverlay();
diff --git a/src/gl/scene/gl_scene.cpp b/src/gl/scene/gl_scene.cpp
index a87e522d3..44368775a 100644
--- a/src/gl/scene/gl_scene.cpp
+++ b/src/gl/scene/gl_scene.cpp
@@ -1019,23 +1019,10 @@ bool FGLInterface::UsesColormap() const
 
 void FGLInterface::PrecacheTexture(FTexture *tex, int cache)
 {
-	if (tex != NULL)
+	if (cache & (FTextureManager::HIT_Wall | FTextureManager::HIT_Flat | FTextureManager::HIT_Sky))
 	{
-		if (cache)
-		{
-			if (gl_precache)
-			{
-				if (cache & (FTextureManager::HIT_Wall | FTextureManager::HIT_Flat | FTextureManager::HIT_Sky))
-				{
-					FMaterial * gltex = FMaterial::ValidateTexture(tex, false);
-					if (gltex) gltex->Precache();
-				}
-			}
-		}
-		else
-		{
-			if (tex->gl_info.Material[0]) tex->gl_info.Material[0]->Clean(true);
-		}
+		FMaterial * gltex = FMaterial::ValidateTexture(tex, false);
+		if (gltex) gltex->Precache();
 	}
 }
 
@@ -1047,15 +1034,8 @@ void FGLInterface::PrecacheTexture(FTexture *tex, int cache)
 
 void FGLInterface::PrecacheSprite(FTexture *tex, SpriteHits &hits)
 {
-	if (hits.CountUsed() == 0)
-	{
-		if (tex->gl_info.Material[1]) tex->gl_info.Material[1]->Clean(true);
-	}
-	else
-	{
-		FMaterial * gltex = FMaterial::ValidateTexture(tex, true);
-		if (gltex) gltex->PrecacheList(hits);
-	}
+	FMaterial * gltex = FMaterial::ValidateTexture(tex, true);
+	if (gltex) gltex->PrecacheList(hits);
 }
 
 //==========================================================================
@@ -1070,6 +1050,8 @@ void FGLInterface::Precache(BYTE *texhitlist, TMap<PClassActor*, bool> &actorhit
 	SpriteHits **spritehitlist = new SpriteHits*[TexMan.NumTextures()];
 	TMap<PClassActor*, bool>::Iterator it(actorhitlist);
 	TMap<PClassActor*, bool>::Pair *pair;
+	BYTE *modellist = new BYTE[Models.Size()];
+	memset(modellist, 0, Models.Size());
 	memset(spritehitlist, 0, sizeof(SpriteHits**) * TexMan.NumTextures());
 
 	// this isn't done by the main code so it needs to be done here first:
@@ -1095,6 +1077,9 @@ void FGLInterface::Precache(BYTE *texhitlist, TMap<PClassActor*, bool> &actorhit
 		}
 	}
 
+	// Check all used actors.
+	// 1. mark all sprites associated with its states
+	// 2. mark all model data and skins associated with its states
 	while (it.NextPair(pair))
 	{
 		PClassActor *cls = pair->Key;
@@ -1103,11 +1088,29 @@ void FGLInterface::Precache(BYTE *texhitlist, TMap<PClassActor*, bool> &actorhit
 		for (int i = 0; i < cls->NumOwnedStates; i++)
 		{
 			spritelist[cls->OwnedStates[i].sprite].Insert(gltrans, true);
+			FSpriteModelFrame * smf = gl_FindModelFrame(cls, cls->OwnedStates[i].sprite, cls->OwnedStates[i].Frame, false);
+			if (smf != NULL)
+			{
+				for (int i = 0; i < MAX_MODELS_PER_FRAME; i++)
+				{
+					if (smf->skinIDs[i].isValid())
+					{
+						texhitlist[smf->skinIDs[i].GetIndex()] |= FTexture::TEX_Flat;
+					}
+					else if (smf->modelIDs[i] != -1)
+					{
+						Models[smf->modelIDs[i]]->AddSkins(texhitlist);
+					}
+					if (smf->modelIDs[i] != -1)
+					{
+						modellist[smf->modelIDs[i]] = 1;
+					}
+				}
+			}
 		}
 	}
 
-	// Precache textures (and sprites).
-
+	// mark all sprite textures belonging to the marked sprites.
 	for (int i = (int)(sprites.Size() - 1); i >= 0; i--)
 	{
 		if (spritelist[i].CountUsed())
@@ -1129,14 +1132,59 @@ void FGLInterface::Precache(BYTE *texhitlist, TMap<PClassActor*, bool> &actorhit
 		}
 	}
 
+	// delete everything unused before creating any new resources to avoid memory usage peaks.
+
+	// delete unused models
+	for (unsigned i = 0; i < Models.Size(); i++)
+	{
+		if (!modellist[i]) Models[i]->DestroyVertexBuffer();
+	}
+
+	// delete unused textures
 	int cnt = TexMan.NumTextures();
 	for (int i = cnt - 1; i >= 0; i--)
 	{
-		PrecacheTexture(TexMan.ByIndex(i), texhitlist[i]);
-		if (spritehitlist[i] != nullptr) PrecacheSprite(TexMan.ByIndex(i), *spritehitlist[i]);
+		FTexture *tex = TexMan.ByIndex(i);
+		if (tex != nullptr)
+		{
+			if (!texhitlist[i])
+			{
+				if (tex->gl_info.Material[0]) tex->gl_info.Material[0]->Clean(true);
+			}
+			if (spritehitlist[i] == nullptr || (*spritehitlist[i]).CountUsed() == 0)
+			{
+				if (tex->gl_info.Material[1]) tex->gl_info.Material[1]->Clean(true);
+			}
+		}
 	}
+
+	if (gl_precache)
+	{
+		// cache all used textures
+		for (int i = cnt - 1; i >= 0; i--)
+		{
+			FTexture *tex = TexMan.ByIndex(i);
+			if (tex != nullptr)
+			{
+				PrecacheTexture(tex, texhitlist[i]);
+				if (spritehitlist[i] != nullptr && (*spritehitlist[i]).CountUsed() > 0)
+				{
+					PrecacheSprite(tex, *spritehitlist[i]);
+				}
+			}
+		}
+
+		// cache all used models
+		for (unsigned i = 0; i < Models.Size(); i++)
+		{
+			if (modellist[i]) 
+				Models[i]->BuildVertexBuffer();
+		}
+	}
+
 	delete[] spritehitlist;
 	delete[] spritelist;
+	delete[] modellist;
 }
 
 
diff --git a/src/gl/scene/gl_sprite.cpp b/src/gl/scene/gl_sprite.cpp
index 3f90b251e..c85de8a0d 100644
--- a/src/gl/scene/gl_sprite.cpp
+++ b/src/gl/scene/gl_sprite.cpp
@@ -287,8 +287,8 @@ void GLSprite::Draw(int pass)
 				if (drawBillboardFacingCamera) {
 					// [CMB] Rotate relative to camera XY position, not just camera direction,
 					// which is nicer in VR
-					float xrel = xcenter - GLRenderer->mViewActor->X();
-					float yrel = ycenter - GLRenderer->mViewActor->Y();
+					float xrel = xcenter - ViewPos.X;
+					float yrel = ycenter - ViewPos.Y;
 					float absAngleDeg = RAD2DEG(atan2(-yrel, xrel));
 					float counterRotationDeg = 270. - GLRenderer->mAngles.Yaw.Degrees; // counteracts existing sprite rotation
 					float relAngleDeg = counterRotationDeg + absAngleDeg;
diff --git a/src/gl/scene/gl_wall.h b/src/gl/scene/gl_wall.h
index 0d8096e76..fdf78ee6f 100644
--- a/src/gl/scene/gl_wall.h
+++ b/src/gl/scene/gl_wall.h
@@ -171,10 +171,13 @@ public:
 private:
 
 	void CheckGlowing();
+	bool PutWallCompat(int passflag);
 	void PutWall(bool translucent);
 	void PutPortal(int ptype);
 	void CheckTexturePosition();
 
+	void RenderFogBoundaryCompat();
+
 	void Put3DWall(lightlist_t * lightlist, bool translucent);
 	void SplitWallComplex(sector_t * frontsector, bool translucent, float maplightbottomleft, float maplightbottomright);
 	void SplitWall(sector_t * frontsector, bool translucent);
diff --git a/src/gl/scene/gl_walls.cpp b/src/gl/scene/gl_walls.cpp
index ae7cb70c8..906f7f3e1 100644
--- a/src/gl/scene/gl_walls.cpp
+++ b/src/gl/scene/gl_walls.cpp
@@ -139,6 +139,11 @@ void GLWall::PutWall(bool translucent)
 	}
 	else
 	{
+		if (gl.lightmethod == LM_SOFTWARE && !translucent)
+		{
+			// This is not yet ready.
+			//if (PutWallCompat(passflag[type])) return;
+		}
 
 		bool masked;
 
diff --git a/src/gl/scene/gl_walls_draw.cpp b/src/gl/scene/gl_walls_draw.cpp
index 8fe9d948e..9fe120ae2 100644
--- a/src/gl/scene/gl_walls_draw.cpp
+++ b/src/gl/scene/gl_walls_draw.cpp
@@ -228,16 +228,23 @@ void GLWall::RenderFogBoundary()
 {
 	if (gl_fogmode && gl_fixedcolormap == 0)
 	{
-		int rel = rellight + getExtraLight();
-		gl_SetFog(lightlevel, rel, &Colormap, false);
-		gl_RenderState.SetEffect(EFF_FOGBOUNDARY);
-		gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
-		glEnable(GL_POLYGON_OFFSET_FILL);
-		glPolygonOffset(-1.0f, -128.0f);
-		RenderWall(RWF_BLANK);
-		glPolygonOffset(0.0f, 0.0f);
-		glDisable(GL_POLYGON_OFFSET_FILL);
-		gl_RenderState.SetEffect(EFF_NONE);
+		if (gl.glslversion > 0.f)
+		{
+			int rel = rellight + getExtraLight();
+			gl_SetFog(lightlevel, rel, &Colormap, false);
+			gl_RenderState.SetEffect(EFF_FOGBOUNDARY);
+			gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
+			glEnable(GL_POLYGON_OFFSET_FILL);
+			glPolygonOffset(-1.0f, -128.0f);
+			RenderWall(RWF_BLANK);
+			glPolygonOffset(0.0f, 0.0f);
+			glDisable(GL_POLYGON_OFFSET_FILL);
+			gl_RenderState.SetEffect(EFF_NONE);
+		}
+		else
+		{
+			RenderFogBoundaryCompat();
+		}
 	}
 }
 
@@ -255,12 +262,19 @@ void GLWall::RenderMirrorSurface()
 	Vector v(glseg.y2-glseg.y1, 0 ,-glseg.x2+glseg.x1);
 	v.Normalize();
 
-	// we use texture coordinates and texture matrix to pass the normal stuff to the shader so that the default vertex buffer format can be used as is.
-	lolft.u = lorgt.u = uplft.u = uprgt.u = v.X();
-	lolft.v = lorgt.v = uplft.v = uprgt.v = v.Z();
+	if (gl.glslversion >= 0.f)
+	{
+		// we use texture coordinates and texture matrix to pass the normal stuff to the shader so that the default vertex buffer format can be used as is.
+		lolft.u = lorgt.u = uplft.u = uprgt.u = v.X();
+		lolft.v = lorgt.v = uplft.v = uprgt.v = v.Z();
 
-	gl_RenderState.EnableTextureMatrix(true);
-	gl_RenderState.mTextureMatrix.computeNormalMatrix(gl_RenderState.mViewMatrix);
+		gl_RenderState.EnableTextureMatrix(true);
+		gl_RenderState.mTextureMatrix.computeNormalMatrix(gl_RenderState.mViewMatrix);
+	}
+	else
+	{
+		glNormal3fv(&v[0]);
+	}
 
 	// Use sphere mapping for this
 	gl_RenderState.SetEffect(EFF_SPHEREMAP);
diff --git a/src/gl/system/gl_interface.cpp b/src/gl/system/gl_interface.cpp
index e6e802e5c..7d091ebb6 100644
--- a/src/gl/system/gl_interface.cpp
+++ b/src/gl/system/gl_interface.cpp
@@ -168,7 +168,7 @@ void gl_LoadExtensions()
 	gl.vendorstring = (char*)glGetString(GL_VENDOR);
 	gl.lightmethod = LM_SOFTWARE;
 
-	if (gl.version >= 3.3f || CheckExtension("GL_ARB_sampler_objects"))
+	if ((gl.version >= 3.3f || CheckExtension("GL_ARB_sampler_objects")) && !Args->CheckParm("-nosampler"))
 	{
 		gl.flags |= RFL_SAMPLER_OBJECTS;
 	}
diff --git a/src/gl/system/gl_load.c b/src/gl/system/gl_load.c
index 9b89f2880..aed4e0ff8 100644
--- a/src/gl/system/gl_load.c
+++ b/src/gl/system/gl_load.c
@@ -42,6 +42,8 @@ static void* SunGetProcAddress (const GLubyte* name)
 #if defined(_WIN32)
 
 #ifdef _MSC_VER
+// disable inlining here because it creates an incredible amount of bloat in this file.
+#pragma inline_depth(0)
 #pragma warning(disable: 4055)
 #pragma warning(disable: 4054)
 #pragma warning(disable: 4996)
diff --git a/src/gl/textures/gl_material.cpp b/src/gl/textures/gl_material.cpp
index 5207ea00d..6a579b0d5 100644
--- a/src/gl/textures/gl_material.cpp
+++ b/src/gl/textures/gl_material.cpp
@@ -300,7 +300,7 @@ const FHardwareTexture *FGLTexture::Bind(int texunit, int clampmode, int transla
 		translation = GLTranslationPalette::GetInternalTranslation(translation);
 	}
 
-	bool needmipmap = (clampmode <= CLAMP_XY) || !(gl.flags & RFL_SAMPLER_OBJECTS);
+	bool needmipmap = (clampmode <= CLAMP_XY);
 
 	FHardwareTexture *hwtex = CreateHwTexture();
 
@@ -345,9 +345,9 @@ const FHardwareTexture *FGLTexture::Bind(int texunit, int clampmode, int transla
 			}
 			delete[] buffer;
 		}
-		if (!needmipmap) clampmode = CLAMP_XY_NOMIP;
 		if (tex->bHasCanvas) static_cast<FCanvasTexture*>(tex)->NeedUpdate();
-		if (lastSampler != clampmode || lastTranslation != translation)
+		if (translation != lastTranslation) lastSampler = 254;
+		if (lastSampler != clampmode)
 			lastSampler = GLRenderer->mSamplerManager->Bind(texunit, clampmode, lastSampler);
 		lastTranslation = translation;
 		return hwtex; 
diff --git a/src/gl/textures/gl_samplers.cpp b/src/gl/textures/gl_samplers.cpp
index db0193c69..cee2fd894 100644
--- a/src/gl/textures/gl_samplers.cpp
+++ b/src/gl/textures/gl_samplers.cpp
@@ -86,7 +86,6 @@ void FSamplerManager::UnbindAll()
 	{
 		for (int i = 0; i < FHardwareTexture::MAX_TEXTURES; i++)
 		{
-			mLastBound[i] = 0;
 			glBindSampler(i, 0);
 		}
 	}
@@ -97,12 +96,8 @@ BYTE FSamplerManager::Bind(int texunit, int num, int lastval)
 	if (gl.flags & RFL_SAMPLER_OBJECTS)
 	{
 		unsigned int samp = mSamplers[num];
-		//if (samp != mLastBound[texunit])
-		{
-			glBindSampler(texunit, samp);
-			mLastBound[texunit] = samp;
-			return 255;
-		}
+		glBindSampler(texunit, samp);
+		return 255;
 	}
 	else
 	{
@@ -112,7 +107,7 @@ BYTE FSamplerManager::Bind(int texunit, int num, int lastval)
 		case CLAMP_NONE:
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
-			if (lastval > CLAMP_XY_NOMIP)
+			if (lastval >= CLAMP_XY_NOMIP)
 			{
 				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, TexFilter[gl_texture_filter].minfilter);
 				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, TexFilter[gl_texture_filter].magfilter);
@@ -123,7 +118,7 @@ BYTE FSamplerManager::Bind(int texunit, int num, int lastval)
 		case CLAMP_X:
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
-			if (lastval > CLAMP_XY_NOMIP)
+			if (lastval >= CLAMP_XY_NOMIP)
 			{
 				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, TexFilter[gl_texture_filter].minfilter);
 				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, TexFilter[gl_texture_filter].magfilter);
@@ -134,7 +129,18 @@ BYTE FSamplerManager::Bind(int texunit, int num, int lastval)
 		case CLAMP_Y:
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-			if (lastval > CLAMP_XY_NOMIP)
+			if (lastval >= CLAMP_XY_NOMIP)
+			{
+				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, TexFilter[gl_texture_filter].minfilter);
+				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, TexFilter[gl_texture_filter].magfilter);
+				glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, gl_texture_filter_anisotropic);
+			}
+			break;
+
+		case CLAMP_XY:
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+			if (lastval >= CLAMP_XY_NOMIP)
 			{
 				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, TexFilter[gl_texture_filter].minfilter);
 				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, TexFilter[gl_texture_filter].magfilter);
@@ -143,15 +149,11 @@ BYTE FSamplerManager::Bind(int texunit, int num, int lastval)
 			break;
 
 		case CLAMP_XY_NOMIP:
-		case CLAMP_XY:
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-			if (lastval > CLAMP_XY_NOMIP)
-			{
-				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, TexFilter[gl_texture_filter].minfilter);
-				glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, TexFilter[gl_texture_filter].magfilter);
-				glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, gl_texture_filter_anisotropic);
-			}
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, TexFilter[gl_texture_filter].magfilter);
+			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, TexFilter[gl_texture_filter].magfilter);
+			glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 1);
 			break;
 
 		case CLAMP_NOFILTER:
diff --git a/src/gl/textures/gl_samplers.h b/src/gl/textures/gl_samplers.h
index daba65d45..b74d49a33 100644
--- a/src/gl/textures/gl_samplers.h
+++ b/src/gl/textures/gl_samplers.h
@@ -8,7 +8,6 @@ class FSamplerManager
 	// We need 6 different samplers: 4 for the different clamping modes,
 	// one for 2D-textures and one for voxel textures
 	unsigned int mSamplers[7];
-	unsigned int mLastBound[FHardwareTexture::MAX_TEXTURES];
 
 	void UnbindAll();
 
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 003138211..032abbc27 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -5567,6 +5567,11 @@ doplaysound:			if (funcIndex == ACSF_PlayActorSound)
 			if (argCount >= 2)
 			{
 				const char *a, *b;
+				// If the string indicies are the same, then they are the same string.
+				if (args[0] == args[1])
+				{
+					return 0;
+				}
 				a = FBehavior::StaticLookupString(args[0]);
 				b = FBehavior::StaticLookupString(args[1]);
 
diff --git a/src/p_lnspec.cpp b/src/p_lnspec.cpp
index 1ffeb813f..103ac1264 100644
--- a/src/p_lnspec.cpp
+++ b/src/p_lnspec.cpp
@@ -1132,7 +1132,7 @@ FUNC(LS_Teleport_Line)
 
 static void ThrustThingHelper(AActor *it, DAngle angle, double force, INTBOOL nolimit)
 {
-	it->VelFromAngle(angle, force);
+	it->Thrust(angle, force);
 	if (!nolimit)
 	{
 		it->Vel.X = clamp(it->Vel.X, -MAXMOVE, MAXMOVE);