Add +ONLYVISIBLEINMIRRORS and +INVISIBLEINMIRRORS actor flags. The former makes the actor only visible in reflections, while the latter makes the actor not cast reflections in mirrors.

src/rendering/hwrenderer/scene/hw_sprites.cpp

@@ -735,6 +735,17 @@ void HWSprite::Process(HWDrawInfo *di, AActor* thing, sector_t * sector, area_t
 		viewmaster = thing->master;
 	}
 
+	// [Nash] filter visibility in mirrors
+	bool isInMirror = di->mCurrentPortal && (di->mCurrentPortal->mState->MirrorFlag > 0 || di->mCurrentPortal->mState->PlaneMirrorFlag > 0);
+	if (thing->renderflags2 & RF2_INVISIBLEINMIRRORS && isInMirror)
+	{
+		return;
+	}
+	else if (thing->renderflags2 & RF2_ONLYVISIBLEINMIRRORS && !isInMirror)
+	{
+		return;
+	}
+
 	// Some added checks if the camera actor is not supposed to be seen. It can happen that some portal setup has this actor in view in which case it may not be skipped here
 	if (viewmaster == camera && !vp.showviewer)
 	{

src/rendering/swrenderer/scene/r_opaque_pass.cpp

@@ -1028,6 +1028,17 @@ namespace swrenderer
 		if (!renderportal->CurrentPortalInSkybox && renderportal->CurrentPortal && !!P_PointOnLineSidePrecise(thing->Pos(), renderportal->CurrentPortal->dst))
 			return false;
 
+		// [Nash] filter visibility in mirrors
+		bool isInMirror = renderportal != nullptr && renderportal->IsInMirrorRecursively;
+		if (thing->renderflags2 & RF2_INVISIBLEINMIRRORS && isInMirror)
+		{
+			return false;
+		}
+		else if (thing->renderflags2 & RF2_ONLYVISIBLEINMIRRORS && !isInMirror)
+		{
+			return false;
+		}
+
 		double distanceSquared = (thing->Pos() - Thread->Viewport->viewpoint.Pos).LengthSquared();
 		if (distanceSquared > sprite_distance_cull)
 			return false;

src/rendering/swrenderer/scene/r_portal.cpp

@@ -339,6 +339,8 @@ namespace swrenderer
 
 		if (pds->mirror)
 		{
+			IsInMirrorRecursively = true;
+
 			//vertex_t *v1 = ds->curline->v1;
 			vertex_t *v1 = pds->src->v1;
 
@@ -465,6 +467,7 @@ namespace swrenderer
 
 		CurrentPortal = prevpds;
 		MirrorFlags = prevmf;
+		IsInMirrorRecursively = false;
 		viewpoint.Angles.Yaw = startang;
 		viewpoint.Pos = startpos;
 		viewpoint.Path[0] = savedpath[0];

src/rendering/swrenderer/scene/r_portal.h

@@ -48,6 +48,10 @@ namespace swrenderer
 		int WindowRight = 0;
 		uint16_t MirrorFlags = 0;
 
+		// [Nash] this is set when first entering a mirror portal, and is unset when leaving the final mirror portal recursion
+		// Used for the RF2_INVISIBLEINMIRRORS and RF2_ONLYVISIBLEINMIRRORS features
+		bool IsInMirrorRecursively = false;
+
 		PortalDrawseg* CurrentPortal = nullptr;
 		int CurrentPortalUniq = 0;
 		bool CurrentPortalInSkybox = false;