- use the exact sRGB->linear transfer function in HDR mode as the 2.2 gamma approximation is visibly inaccurate in this case

# Conflicts:
#	src/rendering/gl/renderer/gl_postprocess.cpp
#	src/rendering/gl/renderer/gl_stereo3d.cpp
#	src/rendering/hwrenderer/postprocessing/hw_postprocess.h
#	src/rendering/vulkan/renderer/vk_postprocess.cpp
#	wadsrc/static/shaders/glsl/present.fp

# Conflicts:
#	src/gl/renderer/gl_postprocess.cpp
#	src/gl/stereo3d/gl_interleaved3d.cpp
#	src/hwrenderer/postprocessing/hw_presentshader.h

src/gl/renderer/gl_postprocess.cpp

@@ -900,12 +900,12 @@ void FGLRenderer::DrawPresentTexture(const GL_IRECT &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.
-		invgamma *= 2.2f;
-		mPresentShader->InvGamma.Set(invgamma);
+		mPresentShader->HdrMode.Set(1);
 		mPresentShader->ColorScale.Set(static_cast<float>((gl_dither_bpc == -1) ? 1023.0f : (float)((1 << gl_dither_bpc) - 1)));
 	}
 	else
 	{
+		mPresentShader->HdrMode.Set(0);
 		mPresentShader->ColorScale.Set(static_cast<float>((gl_dither_bpc == -1) ? 255.0f : (float)((1 << gl_dither_bpc) - 1)));
 	}
 	mPresentShader->Scale.Set(mScreenViewport.width / (float)mBuffers->GetWidth(), mScreenViewport.height / (float)mBuffers->GetHeight());

src/gl/shaders/gl_presentshader.cpp

@@ -50,6 +50,7 @@ void FPresentShaderBase::Init(const char * vtx_shader_name, const char * program
 	GrayFormula.Init(mShader, "GrayFormula");
 	Scale.Init(mShader, "UVScale");
 	ColorScale.Init(mShader, "ColorScale");
+	HdrMode.Init(mShader, "HdrMode");
 }
 
 void FPresentShader::Bind()

src/gl/shaders/gl_presentshader.h

@@ -16,6 +16,7 @@ public:
 	FBufferedUniform1i GrayFormula;
 	FBufferedUniform2f Scale;
 	FBufferedUniform1f ColorScale;
+	FBufferedUniform1i HdrMode;
 
 protected:
 	virtual void Init(const char * vtx_shader_name, const char * program_name);

src/gl/stereo3d/gl_interleaved3d.cpp

@@ -113,6 +113,7 @@ static void prepareInterleavedPresent(FPresentStereoShaderBase& shader)
 		shader.Saturation.Set(clamp<float>(vid_saturation, -15.0f, 15.0f));
 		shader.GrayFormula.Set(static_cast<int>(gl_satformula));
 	}
+	shader.HdrMode.Set(0);
 	shader.ColorScale.Set(static_cast<float>((gl_dither_bpc == -1) ? 255.0f : (float)((1 << gl_dither_bpc) - 1)));
 	shader.Scale.Set(
 		GLRenderer->mScreenViewport.width / (float)GLRenderer->mBuffers->GetWidth(),

wadsrc/static/shaders/glsl/present.fp

@@ -10,6 +10,7 @@ uniform float Saturation;
 uniform int GrayFormula;
 layout(binding=1) uniform sampler2D DitherTexture;
 uniform float ColorScale;
+uniform int HdrMode;
 
 vec4 ApplyGamma(vec4 c)
 {
@@ -35,7 +36,20 @@ vec4 Dither(vec4 c)
 	return vec4(floor(c.rgb * ColorScale + threshold) / ColorScale, c.a);
 }
 
+vec4 sRGBtoLinear(vec4 c)
+{
+	return vec4(mix(pow((c.rgb + 0.055) / 1.055, vec3(2.4)), c.rgb / 12.92, step(c.rgb, vec3(0.04045))), c.a);
+}
+
+vec4 ApplyHdrMode(vec4 c)
+{
+	if (HdrMode == 0)
+		return c;
+	else
+		return sRGBtoLinear(c);
+}
+
 void main()
 {
-	FragColor = Dither(ApplyGamma(texture(InputTexture, TexCoord)));
+	FragColor = Dither(ApplyHdrMode(ApplyGamma(texture(InputTexture, TexCoord))));
 }