- add vanilla lightmode that behaves exactly as Doom's original light did

src/g_level.cpp

@@ -123,8 +123,9 @@ CUSTOM_CVAR(Bool, gl_notexturefill, false, CVAR_NOINITCALL)
 CUSTOM_CVAR(Int, gl_lightmode, 3, CVAR_ARCHIVE | CVAR_NOINITCALL)
 {
 	int newself = self;
-	if (newself > 4) newself = 8;	// use 8 for software lighting to avoid conflicts with the bit mask
-	if (newself < 0) newself = 0;
+	if (newself > 8) newself = 16;	// use 8 and 16 for software lighting to avoid conflicts with the bit mask
+	else if (newself > 4) newself = 8;
+	else if (newself < 0) newself = 0;
 	if (self != newself) self = newself;
 	else if ((level.info == nullptr || level.info->lightmode == -1)) level.lightmode = self;
 }

src/hwrenderer/scene/hw_drawinfo.cpp

@@ -388,7 +388,7 @@ void HWViewpointUniforms::SetDefaults()
 	mNormalViewMatrix.loadIdentity();
 	mViewHeight = viewheight;
 	mGlobVis = (float)R_GetGlobVis(r_viewwindow, r_visibility) / 32.f;
-	mPalLightLevels = static_cast<int>(gl_bandedswlight) | (static_cast<int>(gl_fogmode) << 8);
+	mPalLightLevels = static_cast<int>(gl_bandedswlight) | (static_cast<int>(gl_fogmode) << 8) | (static_cast<int>(gl_lightmode) << 16);
 	mClipLine.X = -10000000.0f;
 	mShadowmapFilter = gl_shadowmap_filter;
 

src/hwrenderer/scene/hw_renderstate.cpp

@@ -127,7 +127,7 @@ void FRenderState::SetFog(int lightlevel, int rellight, bool fullbright, const F
 	}
 	else
 	{
-		if ((level.lightmode == 2 || (level.lightmode == 8 && cmap->BlendFactor > 0)) && fogcolor == 0)
+		if ((level.lightmode == 2 || (level.lightmode >= 8 && cmap->BlendFactor > 0)) && fogcolor == 0)
 		{
 			float light = (float)hw_CalcLightLevel(lightlevel, rellight, false, cmap->BlendFactor);
 			SetShaderLight(light, lightlevel);
@@ -148,7 +148,7 @@ void FRenderState::SetFog(int lightlevel, int rellight, bool fullbright, const F
 		SetFog(fogcolor, fogdensity);
 
 		// Korshun: fullbright fog like in software renderer.
-		if (level.lightmode == 8 && cmap->BlendFactor == 0 && level.brightfog && fogdensity != 0 && fogcolor != 0)
+		if (level.lightmode >= 8 && cmap->BlendFactor == 0 && level.brightfog && fogdensity != 0 && fogcolor != 0)
 		{
 			SetSoftLightLevel(255);
 		}

src/hwrenderer/scene/hw_renderstate.h

@@ -326,7 +326,7 @@ public:
 
 	void SetSoftLightLevel(int llevel, int blendfactor = 0)
 	{
-		if (level.lightmode == 8 && blendfactor == 0) mLightParms[3] = llevel / 255.f;
+		if (level.lightmode >= 8 && blendfactor == 0) mLightParms[3] = llevel / 255.f;
 		else mLightParms[3] = -1.f;
 	}
 

src/hwrenderer/scene/hw_skyportal.cpp

@@ -165,7 +165,7 @@ void HWSkyPortal::DrawContents(HWDrawInfo *di, FRenderState &state)
 
 	// We have no use for Doom lighting special handling here, so disable it for this function.
 	int oldlightmode = ::level.lightmode;
-	if (::level.lightmode == 8)
+	if (::level.lightmode >= 8)
 	{
 		::level.lightmode = 2;
 		state.SetSoftLightLevel(-1);

src/hwrenderer/scene/hw_weapon.cpp

@@ -107,7 +107,7 @@ void HWDrawInfo::DrawPSprite(HUDSprite *huds, FRenderState &state)
 void HWDrawInfo::DrawPlayerSprites(bool hudModelStep, FRenderState &state)
 {
 	int oldlightmode = level.lightmode;
-	if (!hudModelStep && level.lightmode == 8) level.lightmode = 2;	// Software lighting cannot handle 2D content so revert to lightmode 2 for that.
+	if (!hudModelStep && level.lightmode >= 8) level.lightmode = 2;	// Software lighting cannot handle 2D content so revert to lightmode 2 for that.
 	for (auto &hudsprite : hudsprites)
 	{
 		if ((!!hudsprite.mframe) == hudModelStep)
@@ -260,7 +260,7 @@ static WeaponLighting GetWeaponLighting(sector_t *viewsector, const DVector3 &po
 
 		l.lightlevel = hw_CalcLightLevel(l.lightlevel, getExtraLight(), true, 0);
 
-		if (level.lightmode == 8 || l.lightlevel < 92)
+		if (level.lightmode >= 8 || l.lightlevel < 92)
 		{
 			// Korshun: the way based on max possible light level for sector like in software renderer.
 			double min_L = 36.0 / 31.0 - ((l.lightlevel / 255.0) * (63.0 / 31.0)); // Lightlevel in range 0-63
@@ -499,7 +499,7 @@ void HWDrawInfo::PreparePlayerSprites(sector_t * viewsector, area_t in_area)
 	// hack alert! Rather than changing everything in the underlying lighting code let's just temporarily change
 	// light mode here to draw the weapon sprite.
 	int oldlightmode = level.lightmode;
-	if (level.lightmode == 8) level.lightmode = 2;
+	if (level.lightmode >= 8) level.lightmode = 2;
 
 	for (DPSprite *psp = player->psprites; psp != nullptr && psp->GetID() < PSP_TARGETCENTER; psp = psp->GetNext())
 	{

src/hwrenderer/utility/hw_lighting.cpp

@@ -88,7 +88,7 @@ int hw_CalcLightLevel(int lightlevel, int rellight, bool weapon, int blendfactor
 
 	if (lightlevel == 0) return 0;
 
-	bool darklightmode = (level.lightmode & 2) || (level.lightmode == 8 && blendfactor > 0);
+	bool darklightmode = (level.lightmode & 2) || (level.lightmode >= 8 && blendfactor > 0);
 
 	if (darklightmode && lightlevel < 192 && !weapon) 
 	{
@@ -130,7 +130,7 @@ PalEntry hw_CalcLightColor(int light, PalEntry pe, int blendfactor)
 
 	if (blendfactor == 0)
 	{
-		if (level.lightmode == 8)
+		if (level.lightmode >= 8)
 		{
 			return pe;
 		}
@@ -175,7 +175,7 @@ float hw_GetFogDensity(int lightlevel, PalEntry fogcolor, int sectorfogdensity,
 	float density;
 
 	int lightmode = level.lightmode;
-	if (lightmode == 8 && blendfactor > 0) lightmode = 2;	// The blendfactor feature does not work with software-style lighting.
+	if (lightmode >= 8 && blendfactor > 0) lightmode = 2;	// The blendfactor feature does not work with software-style lighting.
 
 	if (lightmode & 4)
 	{
@@ -190,7 +190,7 @@ float hw_GetFogDensity(int lightlevel, PalEntry fogcolor, int sectorfogdensity,
 	else if ((fogcolor.d & 0xffffff) == 0)
 	{
 		// case 2: black fog
-		if ((lightmode != 8 || blendfactor > 0) && !(level.flags3 & LEVEL3_NOLIGHTFADE))
+		if ((lightmode < 8 || blendfactor > 0) && !(level.flags3 & LEVEL3_NOLIGHTFADE))
 		{
 			density = distfogtable[level.lightmode != 0][hw_ClampLight(lightlevel)];
 		}

wadsrc/static/menudef.txt

@@ -2105,6 +2105,7 @@ OptionValue "LightingModes"
 	3, "$OPTVAL_DARK"
 	4, "$OPTVAL_LEGACY"
 	8, "$OPTVAL_SOFTWARE"
+	16, "$OPTVAL_VANILLA"
 }
 
 OptionValue "Precision"

wadsrc/static/shaders/glsl/main.fp

@@ -119,17 +119,84 @@ vec4 getTexel(vec2 st)
 
 //===========================================================================
 //
-// Doom lighting equation exactly as calculated by zdoom.
+// Vanilla Doom wall colormap equation
+//
+//===========================================================================
+float R_WallColormap(float lightnum, float z)
+{
+	// R_ScaleFromGlobalAngle calculation
+	float projection = 160.0; // projection depends on SCREENBLOCKS!! 160 is the fullscreen value
+	vec3 line_v1 = pixelpos.xyz; // in vanilla this is the first curline vertex
+	vec3 line_normal = vWorldNormal.xyz;
+	float texscale = projection * clamp(dot(normalize(uCameraPos.xyz - line_v1), line_normal), 0.0, 1.0) / z;
+
+	float lightz = clamp(16.0 * texscale, 0.0, 47.0);
+
+	// scalelight[lightnum][lightz] lookup
+	float startmap = (15.0 - lightnum) * 4.0;
+	return startmap - lightz * 0.5;
+}
+
+//===========================================================================
+//
+// Vanilla Doom plane colormap equation
+//
+//===========================================================================
+float R_PlaneColormap(float lightnum, float z)
+{
+	float lightz = clamp(z / 16.0f, 0.0, 127.0);
+
+	// zlight[lightnum][lightz] lookup
+	float startmap = (15.0 - lightnum) * 4.0;
+	float scale = 160.0 / (lightz + 1.0);
+	return startmap - scale * 0.5;
+}
+
+//===========================================================================
+//
+// zdoom colormap equation
+//
+//===========================================================================
+float R_ZDoomColormap(float light, float z)
+{
+	float L = light * 255.0;
+	float vis = min(uGlobVis / z, 24.0 / 32.0);
+	float shade = 2.0 - (L + 12.0) / 128.0;
+	float lightscale = shade - vis;
+	return lightscale * 31.0;
+}
+
+float R_DoomColormap(float light, float z)
+{
+	if ((uPalLightLevels >> 16) == 16) // gl_lightmode 16
+	{
+		float lightnum = clamp(light * 15.0, 0.0, 15.0);
+
+		if (dot(vWorldNormal.xyz, vWorldNormal.xyz) > 0.5)
+		{
+			return mix(R_WallColormap(lightnum, z), R_PlaneColormap(lightnum, z), abs(vWorldNormal.y));
+		}
+		else // vWorldNormal is not set on sprites
+		{
+			return R_PlaneColormap(lightnum, z);
+		}
+	}
+	else
+	{
+		return R_ZDoomColormap(light, z);
+	}
+}
+
+//===========================================================================
+//
+// Doom software lighting equation
 //
 //===========================================================================
 float R_DoomLightingEquation(float light)
 {
-	// L is the integer light level used in the game
-	float L = light * 255.0;
-
-	// z is the depth in view/eye space, positive going into the screen
+	// z is the depth in view space, positive going into the screen
 	float z;
-	if ((uPalLightLevels >> 8) == 2)
+	if (((uPalLightLevels >> 8)  & 0xff) == 2)
 	{
 		z = distance(pixelpos.xyz, uCameraPos.xyz);
 	}
@@ -138,17 +205,13 @@ float R_DoomLightingEquation(float light)
 		z = pixelpos.w;
 	}
 
-	// The zdoom light equation
-	float vis = min(uGlobVis / z, 24.0 / 32.0);
-	float shade = 2.0 - (L + 12.0) / 128.0;
-	float lightscale;
+	float colormap = R_DoomColormap(light, z);
+
 	if ((uPalLightLevels & 0xff) != 0)
-		lightscale = float(-floor(-(shade - vis) * 31.0) - 0.5) / 31.0;
-	else
-		lightscale = shade - vis;
+		colormap = floor(colormap) + 0.5;
 
 	// Result is the normalized colormap index (0 bright .. 1 dark)
-	return clamp(lightscale, 1.0 - light, 31.0 / 32.0);
+	return clamp(colormap, 0.0, 31.0) / 32.0;
 }
 
 //===========================================================================