tr_backend: fix FXAA sampling by using GL_LINEAR on currentRender

- fix FXAA by using GL_LINEAR on currentRender,
- restore GL_NEAREST after that to not break other effects.

Author: illwieckz

src/engine/renderer/GLUtils.h

@@ -140,6 +140,7 @@ struct GLConfig
 	bool bufferStorageAvailable;
 	bool uniformBufferObjectAvailable;
 	bool mapBufferRangeAvailable;
+	bool samplerObjectsAvailable;
 	bool syncAvailable;
 	bool textureBarrierAvailable;
 	bool halfFloatVertexAvailable;

src/engine/renderer/glsl_source/fxaa_fp.glsl

@@ -46,7 +46,12 @@ ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 
 #insert fxaa3_11_fp
 
+#if defined(HAVE_ARB_bindless_texture)
+uniform sampler2D u_ColorMap_linear;
+#define u_ColorMap u_ColorMap_linear
+#else
 uniform sampler2D	u_ColorMap;
+#endif
 
 #if __VERSION__ > 120
 out vec4 outputColor;

src/engine/renderer/tr_backend.cpp

@@ -1603,7 +1603,7 @@ void RB_RenderSSAO()
 
 void RB_FXAA()
 {
-	if ( !r_FXAA.Get() || !gl_fxaaShader )
+	if ( !r_FXAA.Get() || !gl_fxaaShader || !glConfig.samplerObjectsAvailable )
 	{
 		return;
 	}
@@ -1625,11 +1625,42 @@ void RB_FXAA()
 		GL_BindToTMU( 0, tr.currentRenderImage[backEnd.currentMainFBO] )
 	);
 
+	// FXAA expects GL_LINEAR for the sampling to work.
+	GLuint64 handle = 0;
+
+	if ( glConfig.usingBindlessTextures )
+	{
+		// Set a handler.
+		GLuint texture = tr.currentRenderImage[backEnd.currentMainFBO]->texnum;
+		handle = glGetTextureSamplerHandleARB( texture, tr.linearSampler );
+		glMakeTextureHandleResidentARB( handle );
+		GLuint program = gl_fxaaShader->GetProgram()->id;
+		GLint location = glGetUniformLocation( program, "u_ColorMap_linear" );
+		glUniformHandleui64ARB( location, handle );
+	}
+	else
+	{
+		// Bind a sampler.
+		glBindSampler( 0, tr.linearSampler );
+	}
+
 	// This shader is run last, so let it render to screen.
 	R_BindNullFBO();
 
 	Tess_InstantScreenSpaceQuad();
 
+	// Make sure we didn't break other effects expecting GL_NEAREST.
+	if ( glConfig.usingBindlessTextures )
+	{
+		// Unset the handler.
+		glMakeTextureHandleNonResidentARB( handle );
+	}
+	else
+	{
+		// Unbind the sampler.
+		glBindSampler( 0, 0 );
+	}
+
 	GL_CheckErrors();
 }
 
@@ -1697,7 +1728,7 @@ void RB_CameraPostFX() {
 		GL_BindToTMU( 0, tr.currentRenderImage[backEnd.currentMainFBO] ) 
 	);
 
-	if ( r_FXAA.Get() && gl_fxaaShader )
+	if ( r_FXAA.Get() && gl_fxaaShader && glConfig.samplerObjectsAvailable )
 	{
 		// Swap main FBOs.
 		backEnd.currentMainFBO = 1 - backEnd.currentMainFBO;
@@ -3848,6 +3879,12 @@ void R_ShutdownBackend()
 		glDisableVertexAttribArray( i );
 	}
 	glState.vertexAttribsState = 0;
+
+	if ( tr.linearSampler )
+	{
+		glDeleteSamplers( 1, &tr.linearSampler );
+		tr.linearSampler = 0;
+	}
 }
 
 const RenderCommand *EndOfListCommand::ExecuteSelf( ) const

src/engine/renderer/tr_local.h

@@ -2595,6 +2595,8 @@ enum
 		float         inverseSawToothTable[ FUNCTABLE_SIZE ];
 
 		scissorState_t scissor;
+
+		GLuint linearSampler;
 	};
 
 	extern const matrix_t quakeToOpenGLMatrix;

src/engine/renderer/tr_shade.cpp

@@ -222,6 +222,8 @@ static void GLSL_InitGPUShadersOrError()
 
 	GL_CheckErrors();
 
+	bool requireLinearSampler = false;
+
 	gl_shaderManager.InitDriverInfo();
 
 	/* It must be done before GenerateBuiltinHeaders() because glConfig.realtimeLighting
@@ -374,6 +376,15 @@ static void GLSL_InitGPUShadersOrError()
 		gl_shaderManager.LoadShader( gl_fxaaShader );
 
 		gl_fxaaShader->MarkProgramForBuilding();
+
+		requireLinearSampler = true;
+	}
+
+	if ( requireLinearSampler && !tr.linearSampler )
+	{
+		glGenSamplers( 1, &tr.linearSampler );
+		glSamplerParameteri( tr.linearSampler, GL_TEXTURE_MAG_FILTER, GL_LINEAR) ;
+		glSamplerParameteri( tr.linearSampler, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
 	}
 
 	gl_shaderManager.PostProcessGlobalUniforms();

src/engine/sys/sdl_glimp.cpp

@@ -90,6 +90,8 @@ static Cvar::Cvar<bool> r_arb_multi_draw_indirect( "r_arb_multi_draw_indirect",
 	"Use GL_ARB_multi_draw_indirect if available", Cvar::NONE, true );
 static Cvar::Cvar<bool> r_arb_program_interface_query( "r_arb_program_interface_query",
 	"Load GL_ARB_program_interface_query if available", Cvar::NONE, true );
+static Cvar::Cvar<bool> r_arb_sampler_objects( "r_arb_sampler_objects",
+	"Use GL_ARB_sampler_objects if available", Cvar::NONE, true );
 static Cvar::Cvar<bool> r_arb_shader_draw_parameters( "r_arb_shader_draw_parameters",
 	"Use GL_ARB_shader_draw_parameters if available", Cvar::NONE, true );
 static Cvar::Cvar<bool> r_arb_shader_atomic_counters( "r_arb_shader_atomic_counters",
@@ -2018,6 +2020,7 @@ static void GLimp_InitExtensions()
 	Cvar::Latch( r_arb_internalformat_query2 );
 	Cvar::Latch( r_arb_map_buffer_range );
 	Cvar::Latch( r_arb_multi_draw_indirect );
+	Cvar::Latch( r_arb_sampler_objects );
 	Cvar::Latch( r_arb_shader_atomic_counters );
 	Cvar::Latch( r_arb_shader_atomic_counter_ops );
 	Cvar::Latch( r_arb_shader_draw_parameters );
@@ -2374,6 +2377,9 @@ static void GLimp_InitExtensions()
 	// made required in OpenGL 3.0
 	glConfig.mapBufferRangeAvailable = LOAD_EXTENSION_WITH_TEST( ExtFlag_CORE, ARB_map_buffer_range, r_arb_map_buffer_range.Get() );
 
+	// made required in OpenGL 3.3
+	glConfig.samplerObjectsAvailable = LOAD_EXTENSION_WITH_TEST( ExtFlag_NONE, ARB_sampler_objects, r_arb_sampler_objects.Get() );
+
 	// made required in OpenGL 3.2
 	glConfig.syncAvailable = LOAD_EXTENSION_WITH_TEST( ExtFlag_CORE, ARB_sync, r_arb_sync.Get() );