Add cvar r_overbrightQ3 to simulate its overbright

The Quake 3 overbright implementation worked by scaling up the entire
color buffer. For surfaces that were not lit by precomputed lighting you
had to use cgen identityLighting to cancel out. This breaks a lot of
stuff so this cvar is only for testing.

Author: slipher

src/engine/renderer/gl_shader.cpp

@@ -2897,6 +2897,7 @@ GLShader_cameraEffects::GLShader_cameraEffects( GLShaderManager *manager ) :
 	GLShader( "cameraEffects", ATTR_POSITION | ATTR_TEXCOORD, manager ),
 	u_ColorMap3D( this ),
 	u_CurrentMap( this ),
+	u_GlobalLightFactor( this ),
 	u_ColorModulate( this ),
 	u_TextureMatrix( this ),
 	u_ModelViewProjectionMatrix( this ),

src/engine/renderer/gl_shader.h

@@ -3536,6 +3536,21 @@ class u_Time :
 	}
 };
 
+class u_GlobalLightFactor :
+	GLUniform1f
+{
+public:
+	u_GlobalLightFactor( GLShader *shader ) :
+		GLUniform1f( shader, "u_GlobalLightFactor" )
+	{
+	}
+
+	void SetUniform_GlobalLightFactor( float value )
+	{
+		this->SetValue( value );
+	}
+};
+
 class GLDeformStage :
 	public u_Time
 {
@@ -4459,6 +4474,7 @@ class GLShader_cameraEffects :
 	public GLShader,
 	public u_ColorMap3D,
 	public u_CurrentMap,
+	public u_GlobalLightFactor,
 	public u_ColorModulate,
 	public u_TextureMatrix,
 	public u_ModelViewProjectionMatrix,

src/engine/renderer/glsl_source/cameraEffects_fp.glsl

@@ -29,6 +29,7 @@ uniform sampler3D u_ColorMap3D;
 #endif
 
 uniform vec4      u_ColorModulate;
+uniform float     u_GlobalLightFactor; // 1 / tr.identityLight
 uniform float     u_InverseGamma;
 
 IN(smooth) vec2		var_TexCoords;
@@ -55,6 +56,7 @@ void main()
 	vec2 st = gl_FragCoord.st / r_FBufSize;
 
 	vec4 color = texture2D(u_CurrentMap, st);
+	color *= u_GlobalLightFactor;
 
 	if( u_Tonemap ) {
 		color.rgb = TonemapLottes( color.rgb * u_TonemapExposure );

src/engine/renderer/tr_backend.cpp

@@ -3350,6 +3350,7 @@ void RB_CameraPostFX()
 	// enable shader, set arrays
 	gl_cameraEffectsShader->BindProgram( 0 );
 
+	gl_cameraEffectsShader->SetUniform_GlobalLightFactor( 1.0f / tr.identityLight );
 	gl_cameraEffectsShader->SetUniform_ColorModulate( backEnd.viewParms.gradingWeights );
 
 	gl_cameraEffectsShader->SetUniform_InverseGamma( 1.0 / r_gamma->value );

src/engine/renderer/tr_bsp.cpp

@@ -3877,14 +3877,7 @@ static void R_LoadFogs( lump_t *l, lump_t *brushesLump, lump_t *sidesLump )
 		out->fogParms = shader->fogParms;
 
 		out->color = Color::Adapt( shader->fogParms.color );
-
-		/* Historically it was done:
-
-			out->color *= tr.identityLight;
-
-		But tr.identityLight is always 1.0f in Dæmon engine
-		as the as the overbright bit implementation is fully
-		software. */
+		out->color *= tr.identityLight;
 
 		out->color.SetAlpha( 1 );
 
@@ -5126,6 +5119,7 @@ void RE_LoadWorldMap( const char *name )
 	tr.worldLight = tr.lightMode;
 	tr.modelLight = lightMode_t::FULLBRIGHT;
 	tr.modelDeluxe = deluxeMode_t::NONE;
+	tr.mapLightFactor = tr.identityLight = 1.0f;
 
 	// Use fullbright lighting for everything if the world is fullbright.
 	if ( tr.worldLight != lightMode_t::FULLBRIGHT )
@@ -5197,11 +5191,19 @@ 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. */
+	/* Set GLSL overbright parameters if the lighting mode is not fullbright. */
 	if ( tr.lightMode != lightMode_t::FULLBRIGHT )
 	{
-		tr.mapLightFactor = float( 1 << tr.overbrightBits );
+		if ( r_overbrightQ3.Get() )
+		{
+			// light factor is applied to entire color buffer; identityLight can be used to cancel it
+			tr.identityLight = 1.0f / float( 1 << tr.overbrightBits );
+		}
+		else
+		{
+			// light factor is applied wherever a precomputed light is sampled
+			tr.mapLightFactor = float( 1 << tr.overbrightBits );
+		}
 	}
 
 	tr.worldLoaded = true;

src/engine/renderer/tr_init.cpp

@@ -93,6 +93,7 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 	cvar_t      *r_precomputedLighting;
 	Cvar::Cvar<int> r_overbrightDefaultExponent("r_overbrightDefaultExponent", "default map light color shift (multiply by 2^x)", Cvar::NONE, 2);
 	Cvar::Range<Cvar::Cvar<int>> r_overbrightBits("r_overbrightBits", "clamp lightmap colors to 2^x", Cvar::NONE, 1, 0, 3);
+	Cvar::Cvar<bool> r_overbrightQ3("r_overbrightQ3", "brighten entire color buffer like Quake 3 (incompatible with newer assets)", Cvar::NONE, false);
 	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 );
@@ -1186,6 +1187,7 @@ ScreenshotCmd screenshotPNGRegistration("screenshotPNG", ssFormat_t::SSF_PNG, "p
 		r_precomputedLighting = Cvar_Get( "r_precomputedLighting", "1", CVAR_CHEAT | CVAR_LATCH );
 		Cvar::Latch( r_overbrightDefaultExponent );
 		Cvar::Latch( r_overbrightBits );
+		Cvar::Latch( r_overbrightQ3 );
 		Cvar::Latch( r_overbrightIgnoreMapSettings );
 		Cvar::Latch( r_lightMode );
 		Cvar::Latch( r_colorGrading );

src/engine/renderer/tr_local.h

@@ -825,7 +825,7 @@ enum class shaderProfilerRenderSubGroupsMode {
 	enum class colorGen_t
 	{
 	  CGEN_BAD,
-	  CGEN_IDENTITY_LIGHTING, // Always (1,1,1,1) in Dæmon engine as the overbright bit implementation is fully software.
+	  CGEN_IDENTITY_LIGHTING, // Always (1,1,1,1) in Dæmon engine, unless you set r_overbrightQ3.
 	  CGEN_IDENTITY, // always (1,1,1,1)
 	  CGEN_ENTITY, // grabbed from entity's modulate field
 	  CGEN_ONE_MINUS_ENTITY, // grabbed from 1 - entity.modulate
@@ -2817,8 +2817,10 @@ enum class shaderProfilerRenderSubGroupsMode {
 		int mapOverBrightBits;
 		// min(r_overbrightBits.Get(), mapOverBrightBits)
 		int overbrightBits;
-		// pow(2, overbrightBits)
+		// pow(2, overbrightBits), unless r_overbrightQ3 is on
 		float mapLightFactor;
+		// 1/pow(2, overbrightBits) if r_overbrightQ3 is on
+		float identityLight;
 
 		orientationr_t orientation; // for current entity
 
@@ -2943,6 +2945,7 @@ enum class shaderProfilerRenderSubGroupsMode {
 	extern cvar_t *r_precomputedLighting;
 	extern Cvar::Cvar<int> r_overbrightDefaultExponent;
 	extern Cvar::Range<Cvar::Cvar<int>> r_overbrightBits;
+	extern Cvar::Cvar<bool> r_overbrightQ3;
 	extern Cvar::Cvar<bool> r_overbrightIgnoreMapSettings;
 	extern Cvar::Range<Cvar::Cvar<int>> r_lightMode;
 	extern Cvar::Cvar<bool> r_colorGrading;

src/engine/renderer/tr_shade.cpp

@@ -2321,21 +2321,15 @@ void Tess_ComputeColor( shaderStage_t *pStage )
 	// rgbGen
 	switch ( pStage->rgbGen )
 	{
+		case colorGen_t::CGEN_IDENTITY_LIGHTING:
+			tess.svars.color = Color::Color(tr.identityLight, tr.identityLight, tr.identityLight);
+			break;
+
 		case colorGen_t::CGEN_IDENTITY:
 		case colorGen_t::CGEN_ONE_MINUS_VERTEX:
 		default:
-		case colorGen_t::CGEN_IDENTITY_LIGHTING:
-			/* Historically CGEN_IDENTITY_LIGHTING was done this way:
-
-			  tess.svars.color = Color::White * tr.identityLight;
-
-			But tr.identityLight is always 1.0f in Dæmon engine
-			as the as the overbright bit implementation is fully
-			software. */
-			{
 				tess.svars.color = Color::White;
 				break;
-			}
 
 		case colorGen_t::CGEN_VERTEX:
 			{

src/engine/renderer/tr_shader.cpp

@@ -4847,7 +4847,7 @@ static void CollapseStages()
 
 		bool rgbGen_identity =
 			stages[ i ].rgbGen == colorGen_t::CGEN_IDENTITY
-			|| stages[ i ].rgbGen == colorGen_t::CGEN_IDENTITY_LIGHTING;
+			|| ( stages[ i ].rgbGen == colorGen_t::CGEN_IDENTITY_LIGHTING && !r_overbrightQ3.Get() );
 
 		bool alphaGen_identity =
 			stages[ i ].alphaGen == alphaGen_t::AGEN_IDENTITY;