Implement MSAA

Add `r_msaa`. When set to > 0, an MSAA FBO will be created with that many samples. This FBO will be used for rendering, other than when it requires sampling from current render/depth image. When such rendering is required the MSAA FBO will be blit into the main FBO and vice versa, to resolve the MSAA texture.

Author: VReaperV

src/engine/renderer/Material.cpp

@@ -1062,6 +1062,8 @@ void BindShaderHeatHaze( Material* material ) {
 	gl_heatHazeShaderMaterial->SetUniform_DeformEnable( true );
 
 	// draw to background image
+	TransitionMSAAToMain();
+
 	R_BindFBO( tr.mainFBO[1 - backEnd.currentMainFBO] );
 }
 
@@ -2237,6 +2239,8 @@ void MaterialSystem::RenderMaterial( Material& material, const uint32_t viewID )
 		R_BindFBO( tr.mainFBO[backEnd.currentMainFBO] );
 
 		RenderIndirect( material, viewID );
+
+		TransitionMainToMSAA();
 	}
 
 	if ( r_showTris->integer

src/engine/renderer/tr_backend.cpp

@@ -199,6 +199,53 @@ GLuint64 GL_BindToTMU( int unit, image_t *image )
 	return 0;
 }
 
+static void BlitFBOToMSAA( FBO_t* fbo ) {
+	glState.currentFBO = nullptr;
+
+	R_BindFBO( GL_READ_FRAMEBUFFER, fbo );
+	R_BindFBO( GL_DRAW_FRAMEBUFFER, tr.msaaFBO );
+	glBlitFramebuffer( 0, 0, fbo->width, fbo->height, 0, 0, tr.msaaFBO->width, tr.msaaFBO->height,
+		GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT, GL_NEAREST );
+
+	glState.currentFBO = nullptr;
+	R_BindFBO( GL_DRAW_FRAMEBUFFER, fbo );
+	glState.currentFBO = fbo;
+}
+
+static void BlitMSAAToFBO( FBO_t* fbo ) {
+	glState.currentFBO = nullptr;
+
+	R_BindFBO( GL_READ_FRAMEBUFFER, tr.msaaFBO );
+	R_BindFBO( GL_DRAW_FRAMEBUFFER, fbo );
+	glBlitFramebuffer( 0, 0, tr.msaaFBO->width, tr.msaaFBO->height, 0, 0, fbo->width, fbo->height,
+		GL_COLOR_BUFFER_BIT /* | GL_DEPTH_BUFFER_BIT */, GL_NEAREST );
+
+	glState.currentFBO = nullptr;
+	R_BindFBO( GL_READ_FRAMEBUFFER, fbo );
+	glState.currentFBO = fbo;
+}
+
+void TransitionMainToMSAA() {
+	if ( glConfig.MSAA ) {
+		BlitFBOToMSAA( tr.mainFBO[backEnd.currentMainFBO] );
+		R_BindFBO( tr.msaaFBO );
+	}
+}
+
+void TransitionMSAAToMain() {
+	if ( glConfig.MSAA ) {
+		BlitMSAAToFBO( tr.mainFBO[backEnd.currentMainFBO] );
+	}
+}
+
+void BindMSAAOrMainFBO() {
+	if ( glConfig.MSAA ) {
+		R_BindFBO( tr.msaaFBO );
+	} else {
+		R_BindFBO( tr.mainFBO[backEnd.currentMainFBO] );
+	}
+}
+
 void GL_BlendFunc( GLenum sfactor, GLenum dfactor )
 {
 	if ( glState.blendSrc != ( signed ) sfactor || glState.blendDst != ( signed ) dfactor )
@@ -797,7 +844,13 @@ void GL_TexImage2D( GLenum target, GLint level, GLint internalFormat, GLsizei wi
 	GLint finalFormat = GL_ToSRGB( internalFormat, isSRGB );
 
 	glTexImage2D( target, level, finalFormat, width, height, border, format, type, data );
+}
+
+void GL_TexImage2DMultisample( GLenum target, GLsizei samples, GLint internalFormat, GLsizei width, GLsizei height, bool fixedSampleLocations, bool isSRGB )
+{
+	GLint finalFormat = GL_ToSRGB( internalFormat, isSRGB );
 
+	glTexImage2DMultisample( target, samples, finalFormat, width, height, fixedSampleLocations );
 }
 
 void GL_TexImage3D( GLenum target, GLint level, GLint internalFormat, GLsizei width, GLsizei height, GLsizei depth, GLint border, GLenum format, GLenum type, const void *data, bool isSRGB )
@@ -1365,7 +1418,8 @@ void RB_RenderPostDepthLightTile()
 	Tess_Clear();
 
 	// back to main image
-	R_BindFBO( tr.mainFBO[ backEnd.currentMainFBO ] );
+	BindMSAAOrMainFBO();
+
 	GL_Viewport( backEnd.viewParms.viewportX, backEnd.viewParms.viewportY,
 		     backEnd.viewParms.viewportWidth, backEnd.viewParms.viewportHeight );
 	GL_Scissor( backEnd.viewParms.scissorX, backEnd.viewParms.scissorY,
@@ -1446,6 +1500,8 @@ void RB_RenderBloom()
 			GL_BindToTMU( 0, tr.currentRenderImage[backEnd.currentMainFBO] )
 		);
 
+		TransitionMSAAToMain();
+
 		R_BindFBO( tr.contrastRenderFBO );
 		GL_ClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
 		glClear( GL_COLOR_BUFFER_BIT );
@@ -1510,6 +1566,8 @@ void RB_RenderBloom()
 		GL_PopMatrix();
 	}
 
+	TransitionMainToMSAA();
+
 	GL_CheckErrors();
 }
 
@@ -1530,6 +1588,8 @@ void RB_RenderMotionBlur()
 
 	gl_motionblurShader->BindProgram();
 
+	TransitionMSAAToMain();
+
 	// Swap main FBOs
 	gl_motionblurShader->SetUniform_ColorMapBindless(
 		GL_BindToTMU( 0, tr.currentRenderImage[backEnd.currentMainFBO] )
@@ -1545,6 +1605,8 @@ void RB_RenderMotionBlur()
 
 	Tess_InstantScreenSpaceQuad();
 
+	TransitionMainToMSAA();
+
 	GL_CheckErrors();
 }
 
@@ -2666,7 +2728,7 @@ static void RB_RenderView( bool depthPass )
 	backEnd.pc.c_surfaces += backEnd.viewParms.numDrawSurfs;
 
 	// disable offscreen rendering
-	R_BindFBO( tr.mainFBO[ backEnd.currentMainFBO ] );
+	BindMSAAOrMainFBO();
 
 	// we will need to change the projection matrix before drawing
 	// 2D images again
@@ -2794,6 +2856,8 @@ static void RB_RenderPostProcess()
 		materialSystem.EndFrame();
 	}
 
+	TransitionMSAAToMain();
+
 	RB_FXAA();
 
 	// render chromatic aberration
@@ -3463,7 +3527,7 @@ const RenderCommand *ClearBufferCommand::ExecuteSelf( ) const
 	}
 
 	// disable offscreen rendering
-	R_BindFBO( tr.mainFBO[ backEnd.currentMainFBO ] );
+	R_BindFBO( tr.mainFBO[backEnd.currentMainFBO] );
 
 	// we will need to change the projection matrix before drawing
 	// 2D images again
@@ -3484,6 +3548,11 @@ const RenderCommand *ClearBufferCommand::ExecuteSelf( ) const
 
 	glClear( clearBits );
 
+	if ( glConfig.MSAA ) {
+		R_BindFBO( tr.msaaFBO );
+		glClear( clearBits );
+	}
+
 	return this + 1;
 }
 

src/engine/renderer/tr_fbo.cpp

@@ -152,7 +152,8 @@ R_AttachFBOTexture2D
 */
 void R_AttachFBOTexture2D( int target, int texId, int index )
 {
-	if ( target != GL_TEXTURE_2D && ( target < GL_TEXTURE_CUBE_MAP_POSITIVE_X || target > GL_TEXTURE_CUBE_MAP_NEGATIVE_Z ) )
+	if ( target != GL_TEXTURE_2D  && target != GL_TEXTURE_2D_MULTISAMPLE
+		&& ( target < GL_TEXTURE_CUBE_MAP_POSITIVE_X || target > GL_TEXTURE_CUBE_MAP_NEGATIVE_Z ) )
 	{
 		Log::Warn("R_AttachFBOTexture2D: invalid target %i", target );
 		return;
@@ -194,6 +195,11 @@ void R_AttachFBOTexturePackedDepthStencil( int texId )
 	GL_fboShim.glFramebufferTexture2D( GL_DRAW_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_TEXTURE_2D, texId, 0 );
 }
 
+void R_AttachFBOTexturePackedDepthStencilMSAA( int texId ) {
+	GL_fboShim.glFramebufferTexture2D( GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D_MULTISAMPLE, texId, 0 );
+	GL_fboShim.glFramebufferTexture2D( GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_TEXTURE_2D_MULTISAMPLE, texId, 0 );
+}
+
 /*
 ============
 R_BindFBO
@@ -271,6 +277,17 @@ void R_InitFBOs()
 		glConfig.usingReadonlyDepth = R_CheckFBO( tr.readonlyDepthFBO );
 	}
 
+	if ( glConfig.MSAA ) {
+		tr.msaaFBO = R_CreateFBO( "msaa", width, height );
+		R_BindFBO( tr.msaaFBO );
+		GL_CheckErrors();
+		R_AttachFBOTexture2D( GL_TEXTURE_2D_MULTISAMPLE, tr.currentRenderImageMSAA->texnum, 0 );
+		GL_CheckErrors();
+		R_AttachFBOTexturePackedDepthStencilMSAA( tr.currentDepthImageMSAA->texnum );
+		GL_CheckErrors();
+		R_CheckFBO( tr.msaaFBO );
+	}
+
 	if ( glConfig.realtimeLighting )
 	{
 		/* It's only required to create frame buffers only used by the