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

@@ -1171,6 +1171,9 @@ void BindShaderHeatHaze( Material* material ) {
 	gl_heatHazeShaderMaterial->SetUniform_DeformEnable( true );
 
 	// draw to background image
+	if ( r_msaa.Get() ) {
+		GL_BlitMSAAToFBO( tr.mainFBO[backEnd.currentMainFBO] );
+	}
 	R_BindFBO( tr.mainFBO[1 - backEnd.currentMainFBO] );
 }
 
@@ -2302,6 +2305,11 @@ void MaterialSystem::RenderMaterial( Material& material, const uint32_t viewID )
 		R_BindFBO( tr.mainFBO[backEnd.currentMainFBO] );
 
 		RenderIndirect( material, viewID );
+
+		if ( r_msaa.Get() ) {
+			GL_BlitFBOToMSAA( tr.mainFBO[backEnd.currentMainFBO] );
+			R_BindFBO( tr.msaaFBO );
+		}
 	}
 
 	if ( r_showTris->integer

src/engine/renderer/tr_backend.cpp

@@ -208,6 +208,26 @@ GLuint64 GL_BindToTMU( int unit, image_t *image )
 	return 0;
 }
 
+void GL_BlitFBOToMSAA( FBO_t* fbo ) {
+	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 );
+
+	R_BindFBO( GL_DRAW_FRAMEBUFFER, fbo );
+	glState.currentFBO = nullptr;
+}
+
+void GL_BlitMSAAToFBO( FBO_t* fbo ) {
+	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 );
+
+	R_BindFBO( GL_READ_FRAMEBUFFER, fbo );
+	glState.currentFBO = nullptr;
+}
+
 void GL_BlendFunc( GLenum sfactor, GLenum dfactor )
 {
 	if ( glState.blendSrc != ( signed ) sfactor || glState.blendDst != ( signed ) dfactor )
@@ -3082,6 +3102,9 @@ void RB_RenderBloom()
 
 		GL_PopMatrix(); // special 1/4th of the screen contrastRenderFBO ortho
 
+		if ( r_msaa.Get() ) {
+			GL_BlitMSAAToFBO( tr.mainFBO[backEnd.currentMainFBO] );
+		}
 		R_BindFBO( tr.contrastRenderFBO );
 		GL_ClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
 		glClear( GL_COLOR_BUFFER_BIT );
@@ -3148,6 +3171,11 @@ void RB_RenderBloom()
 		                  backEnd.viewParms.viewportWidth, backEnd.viewParms.viewportHeight );
 	}
 
+	if ( r_msaa.Get() ) {
+		GL_BlitFBOToMSAA( tr.mainFBO[backEnd.currentMainFBO] );
+		R_BindFBO( tr.msaaFBO );
+	}
+
 	// go back to 3D
 	GL_PopMatrix();
 
@@ -3170,6 +3198,10 @@ void RB_RenderMotionBlur()
 
 	gl_motionblurShader->BindProgram( 0 );
 
+	if ( r_msaa.Get() ) {
+		GL_BlitMSAAToFBO( tr.mainFBO[backEnd.currentMainFBO] );
+	}
+
 	// Swap main FBOs
 	gl_motionblurShader->SetUniform_ColorMapBindless(
 		GL_BindToTMU( 0, tr.currentRenderImage[backEnd.currentMainFBO] )
@@ -3196,6 +3228,11 @@ void RB_RenderMotionBlur()
 	                   backEnd.viewParms.viewportX, backEnd.viewParms.viewportY,
 	                   backEnd.viewParms.viewportWidth, backEnd.viewParms.viewportHeight );
 
+	if ( r_msaa.Get() ) {
+		GL_BlitFBOToMSAA( tr.mainFBO[backEnd.currentMainFBO] );
+		R_BindFBO( tr.msaaFBO );
+	}
+
 	GL_PopMatrix();
 
 	GL_CheckErrors();
@@ -4628,7 +4665,11 @@ static void RB_RenderView( bool depthPass )
 	backEnd.pc.c_surfaces += backEnd.viewParms.numDrawSurfs;
 
 	// disable offscreen rendering
-	R_BindFBO( tr.mainFBO[ backEnd.currentMainFBO ] );
+	if ( r_msaa.Get() ) {
+		R_BindFBO( tr.msaaFBO );
+	} else {
+		R_BindFBO( tr.mainFBO[backEnd.currentMainFBO] );
+	}
 
 	// we will need to change the projection matrix before drawing
 	// 2D images again

src/engine/renderer/tr_fbo.cpp

@@ -303,7 +303,8 @@ 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;
@@ -355,28 +356,34 @@ void R_AttachFBOTexturePackedDepthStencil( int texId )
 	GL_fboShim.glFramebufferTexture2D( GL_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
 ============
 */
 void R_BindFBO( FBO_t *fbo )
 {
-	if ( !fbo )
-	{
+	R_BindFBO( GL_FRAMEBUFFER, fbo );
+}
+
+void R_BindFBO( const GLenum target, FBO_t* fbo ) {
+	if ( !fbo ) {
 		R_BindNullFBO();
 		return;
 	}
 
-	if ( r_logFile->integer )
-	{
+	if ( r_logFile->integer ) {
 		// don't just call LogComment, or we will get a call to va() every frame!
 		GLimp_LogComment( va( "--- R_BindFBO( %s ) ---\n", fbo->name ) );
 	}
 
-	if ( glState.currentFBO != fbo )
-	{
-		GL_fboShim.glBindFramebuffer( GL_FRAMEBUFFER, fbo->frameBuffer );
+	if ( glState.currentFBO != fbo ) {
+		GL_fboShim.glBindFramebuffer( target, fbo->frameBuffer );
 
 		glState.currentFBO = fbo;
 	}
@@ -436,6 +443,17 @@ void R_InitFBOs()
 	R_AttachFBOTexturePackedDepthStencil( tr.currentDepthImage->texnum );
 	R_CheckFBO( tr.mainFBO[1] );
 
+	if( r_msaa.Get() ) {
+		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 ( glConfig2.realtimeLighting
 		&& r_realtimeLightingRenderer.Get() == Util::ordinal( realtimeLightingRenderer_t::TILED ) )
 	{