Implement partial overbright clamping like q3

The lighting values continue to be multiplied by pow(2,
tr.mapOverbrightBits) but the resulting values are capped at
pow(2, tr.overbrightBits) which defaults to 1. This matches
the original behavior of Quake 3 (in full screen mode) and
Tremulous 1.1.0. The cvar r_overbrightBits has come back
and has the same behavior as ioq3.

Setting r_overbrightBits to 0 gives you the behavior of pre-0.55
Unvanquished. Setting r_overbrightBits to 2 gives you 0.55.x behavior.

See #1542 for more
information.

Author: slipher

src/engine/renderer/tr_bsp.cpp

@@ -74,10 +74,7 @@ static void R_ColorShiftLightingBytes( byte bytes[ 4 ] )
 	backward compatible with this bug for diagnostic purpose and fair comparison with
 	other buggy engines. */
 
-	if ( tr.mapOverBrightBits == 0 )
-	{
-		return;
-	}
+	ASSERT_LT( tr.overbrightBits, tr.mapOverBrightBits );
 
 	/* Shift the color data based on overbright range.
 
@@ -94,7 +91,7 @@ static void R_ColorShiftLightingBytes( byte bytes[ 4 ] )
 	what hardware overbright bit feature was not doing, but
 	this implementation is entirely software. */
 
-	int shift = tr.mapOverBrightBits;
+	int shift = tr.mapOverBrightBits - tr.overbrightBits;
 
 	// shift the data based on overbright range
 	int r = bytes[ 0 ] << shift;
@@ -120,10 +117,7 @@ static void R_ColorShiftLightingBytes( byte bytes[ 4 ] )
 
 static void R_ColorShiftLightingBytesCompressed( byte bytes[ 8 ] )
 {
-	if ( tr.mapOverBrightBits == 0 )
-	{
-		return;
-	}
+	ASSERT_LT( tr.overbrightBits, tr.mapOverBrightBits );
 
 	// color shift the endpoint colors in the dxt block
 	unsigned short rgb565 = bytes[1] << 8 | bytes[0];
@@ -164,7 +158,7 @@ R_ProcessLightmap
 */
 void R_ProcessLightmap( byte *bytes, int width, int height, int bits )
 {
-	if ( tr.mapOverBrightBits == 0 )
+	if ( tr.overbrightBits >= tr.mapOverBrightBits )
 	{
 		return;
 	}
@@ -668,7 +662,7 @@ static void R_LoadLightmaps( lump_t *l, const char *bspName )
 					lightMapBuffer[( index * 4 ) + 2 ] = buf_p[( ( x + ( y * internalLightMapSize ) ) * 3 ) + 2 ];
 					lightMapBuffer[( index * 4 ) + 3 ] = 255;
 
-					if ( tr.legacyOverBrightClamping )
+					if ( tr.overbrightBits < tr.mapOverBrightBits )
 					{
 						R_ColorShiftLightingBytes( &lightMapBuffer[( index * 4 ) + 0 ] );
 					}
@@ -1029,7 +1023,7 @@ static void ParseFace( dsurface_t *ds, drawVert_t *verts, bspSurface_t *surf, in
 		cv->verts[ i ].lightColor = Color::Adapt( verts[ i ].color );
 
 
-		if ( tr.legacyOverBrightClamping )
+		if ( tr.overbrightBits < tr.mapOverBrightBits )
 		{
 			R_ColorShiftLightingBytes( cv->verts[ i ].lightColor.ToArray() );
 		}
@@ -1239,7 +1233,7 @@ static void ParseMesh( dsurface_t *ds, drawVert_t *verts, bspSurface_t *surf )
 
 		points[ i ].lightColor = Color::Adapt( verts[ i ].color );
 
-		if ( tr.legacyOverBrightClamping )
+		if ( tr.overbrightBits < tr.mapOverBrightBits )
 		{
 			R_ColorShiftLightingBytes( points[ i ].lightColor.ToArray() );
 		}
@@ -1366,7 +1360,7 @@ static void ParseTriSurf( dsurface_t *ds, drawVert_t *verts, bspSurface_t *surf,
 
 			cv->verts[ i ].lightColor = Color::Adapt( verts[ i ].color );
 
-		if ( tr.legacyOverBrightClamping )
+		if ( tr.overbrightBits < tr.mapOverBrightBits )
 		{
 			R_ColorShiftLightingBytes( cv->verts[ i ].lightColor.ToArray() );
 		}
@@ -4112,7 +4106,7 @@ void R_LoadLightGrid( lump_t *l )
 		tmpDirected[ 2 ] = in->directed[ 2 ];
 		tmpDirected[ 3 ] = 255;
 
-		if ( tr.legacyOverBrightClamping )
+		if ( tr.overbrightBits < tr.mapOverBrightBits )
 		{
 			R_ColorShiftLightingBytes( tmpAmbient );
 			R_ColorShiftLightingBytes( tmpDirected );
@@ -4372,24 +4366,6 @@ void R_LoadEntities( lump_t *l, std::string &externalEntities )
 				tr.mapOverBrightBits = Math::Clamp( atof( value ), 0.0, 3.0 );
 				continue;
 			}
-
-			if ( !Q_stricmp( keyname, "overbrightClamping" ) )
-			{
-				if ( !Q_stricmp( value, "0" ) )
-				{
-					tr.legacyOverBrightClamping = false;
-				}
-				else if ( !Q_stricmp( value, "1" ) )
-				{
-					tr.legacyOverBrightClamping = true;
-				}
-				else
-				{
-					Log::Warn( "invalid value for worldspawn key overbrightClamping" );
-				}
-
-				continue;
-			}
 		}
 
 		// check for deluxe mapping provided by NetRadiant's q3map2
@@ -5122,6 +5098,9 @@ void RE_LoadWorldMap( const char *name )
 	}
 	R_LoadEntities( &header->lumps[ LUMP_ENTITIES ], externalEntities );
 
+	// Now we can set this after checking a possible worldspawn value for mapOverbrightBits
+	tr.overbrightBits = std::min( tr.mapOverBrightBits, r_overbrightBits.Get() );
+
 	R_LoadShaders( &header->lumps[ LUMP_SHADERS ] );
 
 	R_LoadLightmaps( &header->lumps[ LUMP_LIGHTMAPS ], name );
@@ -5159,7 +5138,6 @@ void RE_LoadWorldMap( const char *name )
 	tr.worldLight = tr.lightMode;
 	tr.modelLight = lightMode_t::FULLBRIGHT;
 	tr.modelDeluxe = deluxeMode_t::NONE;
-	tr.mapLightFactor = 1.0f;
 
 	// Use fullbright lighting for everything if the world is fullbright.
 	if ( tr.worldLight != lightMode_t::FULLBRIGHT )
@@ -5233,9 +5211,9 @@ void RE_LoadWorldMap( const char *name )
 
 	/* Set GLSL overbright parameters if the legacy clamped overbright isn't used
 	and the lighting mode is not fullbright. */
-	if ( !tr.legacyOverBrightClamping && tr.lightMode != lightMode_t::FULLBRIGHT )
+	if ( tr.lightMode != lightMode_t::FULLBRIGHT )
 	{
-		tr.mapLightFactor = pow( 2, tr.mapOverBrightBits );
+		tr.mapLightFactor = float( 1 << tr.overbrightBits );
 	}
 
 	tr.worldLoaded = true;

src/engine/renderer/tr_image.cpp

@@ -1853,7 +1853,7 @@ image_t *R_FindImageFile( const char *imageName, imageParams_t &imageParams )
 		return nullptr;
 	}
 
-	if ( imageParams.bits & IF_LIGHTMAP && tr.legacyOverBrightClamping )
+	if ( imageParams.bits & IF_LIGHTMAP )
 	{
 		R_ProcessLightmap( *pic, width, height, imageParams.bits );
 	}
@@ -3054,6 +3054,7 @@ void R_InitImages()
 	tr.lightmaps.reserve( 128 );
 	tr.deluxemaps.reserve( 128 );
 
+	//TODO rewrite WoT with new info :)
 	/* These are the values expected by the rest of the renderer
 	(esp. tr_bsp), used for "gamma correction of the map".
 	Both were set to 0 if we had neither COMPAT_ET nor COMPAT_Q3,
@@ -3113,8 +3114,9 @@ void R_InitImages()
 	Because tr.overbrightBits is always 0, tr.identityLight is
 	always 1.0f. We can entirely remove it. */
 
+	// TODO is there any reason to set these before a map is loaded?
 	tr.mapOverBrightBits = r_overbrightDefaultExponent.Get();
-	tr.legacyOverBrightClamping = r_overbrightDefaultClamp.Get();
+	tr.overbrightBits = std::min(tr.mapOverBrightBits, r_overbrightBits.Get());
 
 	// create default texture and white texture
 	R_CreateBuiltinImages();

src/engine/renderer/tr_init.cpp

@@ -92,7 +92,7 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 	cvar_t      *r_realtimeLightingCastShadows;
 	cvar_t      *r_precomputedLighting;
 	Cvar::Cvar<int> r_overbrightDefaultExponent("r_overbrightDefaultExponent", "default map light color shift (multiply by 2^x)", Cvar::NONE, 2);
-	Cvar::Cvar<bool> r_overbrightDefaultClamp("r_overbrightDefaultClamp", "clamp lightmap colors to 1 (in absence of map worldspawn value)", Cvar::NONE, false);
+	Cvar::Range<Cvar::Cvar<int>> r_overbrightBits("r_overbrightBits", "clamp lightmap colors to 2^x", Cvar::NONE, 1, 0, 3);
 	Cvar::Cvar<bool> r_overbrightIgnoreMapSettings("r_overbrightIgnoreMapSettings", "force usage of r_overbrightDefaultClamp / r_overbrightDefaultExponent, ignoring worldspawn", Cvar::NONE, false);
 	Cvar::Range<Cvar::Cvar<int>> r_lightMode("r_lightMode", "lighting mode: 0: fullbright (cheat), 1: vertex light, 2: grid light (cheat), 3: light map", Cvar::NONE, Util::ordinal(lightMode_t::MAP), Util::ordinal(lightMode_t::FULLBRIGHT), Util::ordinal(lightMode_t::MAP));
 	Cvar::Cvar<bool> r_colorGrading( "r_colorGrading", "Use color grading", Cvar::NONE, true );
@@ -1185,7 +1185,7 @@ ScreenshotCmd screenshotPNGRegistration("screenshotPNG", ssFormat_t::SSF_PNG, "p
 		r_realtimeLightingCastShadows = Cvar_Get( "r_realtimeLightingCastShadows", "1", 0 );
 		r_precomputedLighting = Cvar_Get( "r_precomputedLighting", "1", CVAR_CHEAT | CVAR_LATCH );
 		Cvar::Latch( r_overbrightDefaultExponent );
-		Cvar::Latch( r_overbrightDefaultClamp );
+		Cvar::Latch( r_overbrightBits );
 		Cvar::Latch( r_overbrightIgnoreMapSettings );
 		Cvar::Latch( r_lightMode );
 		Cvar::Latch( r_colorGrading );

src/engine/renderer/tr_local.h

@@ -2809,12 +2809,14 @@ enum class shaderProfilerRenderSubGroupsMode {
 
 		viewParms_t    viewParms;
 
-		// r_overbrightDefaultExponent, but can be overridden by mapper using the worldspawn
+		// Brightness scaling: roughly speaking, a lightmap value of x will be interpreted as
+		// min(x * pow(2, mapOverBrightBits), pow(2, overbrightBits))
+		// (but when a component hits the max allowed value, others are scaled down to keep the "same color")
 		int mapOverBrightBits;
-		// pow(2, mapOverbrightBits)
+		// min(r_overbrightBits.Get(), mapOverBrightBits)
+		int overbrightBits;
+		// pow(2, overbrightBits)
 		float mapLightFactor;
-		// May have to be true on some legacy maps: clamp and normalize multiplied colors.
-		bool legacyOverBrightClamping;
 
 		orientationr_t orientation; // for current entity
 
@@ -2938,7 +2940,7 @@ enum class shaderProfilerRenderSubGroupsMode {
 	extern cvar_t *r_realtimeLightingCastShadows;
 	extern cvar_t *r_precomputedLighting;
 	extern Cvar::Cvar<int> r_overbrightDefaultExponent;
-	extern Cvar::Cvar<bool> r_overbrightDefaultClamp;
+	extern Cvar::Range<Cvar::Cvar<int>> r_overbrightBits;
 	extern Cvar::Cvar<bool> r_overbrightIgnoreMapSettings;
 	extern Cvar::Range<Cvar::Cvar<int>> r_lightMode;
 	extern Cvar::Cvar<bool> r_colorGrading;