- add gl_dither for toggling dithered output on and off

src/gl/renderer/gl_postprocess.cpp

@@ -49,6 +49,8 @@
 
 extern bool vid_hdr_active;
 
+CVAR(Bool, gl_dither, false, CVAR_ARCHIVE | CVAR_GLOBALCONFIG | CVAR_NOINITCALL)
+
 void FGLRenderer::RenderScreenQuad()
 {
 	mVBO->BindVBO();
@@ -234,6 +236,11 @@ void FGLRenderer::DrawPresentTexture(const IntRect &box, bool applyGamma)
 		// Full screen exclusive mode treats a rgba16f frame buffer as linear.
 		// It probably will eventually in desktop mode too, but the DWM doesn't seem to support that.
 		mPresentShader->Uniforms->InvGamma *= 2.2f;
+		mPresentShader->Uniforms->ColorScale = gl_dither ? 1023.0f : 0.0f;
+	}
+	else
+	{
+		mPresentShader->Uniforms->ColorScale = gl_dither ? 255.0f : 0.0f;
 	}
 	mPresentShader->Uniforms->Scale = { screen->mScreenViewport.width / (float)mBuffers->GetWidth(), screen->mScreenViewport.height / (float)mBuffers->GetHeight() };
 	mPresentShader->Uniforms.Set();

src/gl/renderer/gl_stereo3d.cpp

@@ -39,6 +39,7 @@ EXTERN_CVAR(Float, vid_saturation)
 EXTERN_CVAR(Float, vid_brightness)
 EXTERN_CVAR(Float, vid_contrast)
 EXTERN_CVAR(Int, gl_satformula)
+EXTERN_CVAR(Bool, gl_dither)
 
 //==========================================================================
 //
@@ -162,6 +163,7 @@ static void prepareInterleavedPresent(FPresentShaderBase& shader)
 		shader.Uniforms->Saturation = clamp<float>(vid_saturation, -15.0f, 15.0f);
 		shader.Uniforms->GrayFormula = static_cast<int>(gl_satformula);
 	}
+	shader.Uniforms->ColorScale = gl_dither ? 255.0f : 0.0f;
 	shader.Uniforms->Scale = {
 		screen->mScreenViewport.width / (float)GLRenderer->mBuffers->GetWidth(),
 		screen->mScreenViewport.height / (float)GLRenderer->mBuffers->GetHeight()

src/hwrenderer/postprocessing/hw_presentshader.h

@@ -18,6 +18,8 @@ public:
 		int GrayFormula;
 		int WindowPositionParity; // top-of-window might not be top-of-screen
 		FVector2 Scale;
+		float ColorScale;
+		float Padding1, Padding2, Padding3;
 
 		static std::vector<UniformFieldDesc> Desc()
 		{
@@ -30,6 +32,7 @@ public:
 				{ "GrayFormula", UniformType::Int, offsetof(UniformBlock, GrayFormula) },
 				{ "WindowPositionParity", UniformType::Int, offsetof(UniformBlock, WindowPositionParity) },
 				{ "UVScale", UniformType::Vec2, offsetof(UniformBlock, Scale) },
+				{ "ColorScale", UniformType::Float, offsetof(UniformBlock, ColorScale) },
 			};
 		}
 	};

wadsrc/static/language.enu

@@ -2815,6 +2815,7 @@ GLPREFMNU_LENS					= "Lens distortion effect";
 GLPREFMNU_SSAO					= "Ambient occlusion quality";
 GLPREFMNU_SSAO_PORTALS			= "Portals with AO";
 GLPREFMNU_FXAA					= "FXAA Quality";
+GLPREFMNU_DITHER				= "Dither output";
 GLPREFMNU_PALTONEMAPORDER		= "Tonemap Palette Order";
 GLPREFMNU_PALTONEMAPPOWER		= "Tonemap Palette Exponent";
 GLPREFMNU_SWLMBANDED			= "Banded SW Lightmode";

wadsrc/static/menudef.txt

@@ -2286,6 +2286,7 @@ OptionMenu "OpenGLOptions" protected
 	Option "$GLPREFMNU_SSAO",		 			gl_ssao,						"SSAOModes"
 	Slider "$GLPREFMNU_SSAO_PORTALS",			gl_ssao_portals,				0.0, 4.0, 1.0, 0
 	Option "$GLPREFMNU_FXAA",		 			gl_fxaa,						"FXAAQuality"
+	Option "$GLPREFMNU_DITHER",		 			gl_dither,						"OnOff"
 	StaticText " "
 	Slider "$GLPREFMNU_PALTONEMAPPOWER",		gl_paltonemap_powtable,			0.2, 3.0, 0.1, 1
 	Option "$GLPREFMNU_PALTONEMAPORDER",		gl_paltonemap_reverselookup,	"LookupOrder"

wadsrc/static/shaders/glsl/present.fp

@@ -18,14 +18,16 @@ vec4 ApplyGamma(vec4 c)
 	return vec4(val, c.a);
 }
 
-vec4 Dither(vec4 c, float colorscale)
+vec4 Dither(vec4 c)
 {
+	if (ColorScale == 0.0)
+		return c;
 	vec2 texSize = vec2(textureSize(DitherTexture, 0));
 	float threshold = texture(DitherTexture, gl_FragCoord.xy / texSize).r;
-	return vec4(floor(c.rgb * colorscale + threshold) / colorscale, c.a);
+	return vec4(floor(c.rgb * ColorScale + threshold) / ColorScale, c.a);
 }
 
 void main()
 {
-	FragColor = Dither(ApplyGamma(texture(InputTexture, TexCoord)), 255.0);
+	FragColor = Dither(ApplyGamma(texture(InputTexture, TexCoord)));
 }