Add a OneSideEveryOtherFrame reflection probe update mode

trinity/Eve/EveSpaceSceneRenderDriver.cpp

@@ -825,7 +825,7 @@ EveSpaceSceneRenderDriver::ReflectionFaces EveSpaceSceneRenderDriver::PrepareRef
 	ReflectionFaces faces;
 
 	Tr2ReflectionProbe* probe = m_scene->GetReflectionProbe();
-	if( !probe || !probe->IsValid() || !m_scene->m_display )
+	if( !probe || !probe->IsValid() || !m_scene->m_display || !probe->ShouldRenderThisFrame() )
 	{
 		return faces;
 	}

trinity/Tr2ReflectionProbe.cpp

@@ -64,6 +64,16 @@ bool Tr2ReflectionProbe::HasData() const
 	return m_hasData && m_postFilterTarget->IsValid();
 }
 
+bool Tr2ReflectionProbe::ShouldRenderThisFrame() const
+{
+	if( m_renderFrequency != ONE_SIDE_EVERY_OTHER_FRAME || !m_onePassDone )
+	{
+		return true;
+	}
+	// Frame parity rather than a toggle, so the answer stays the same however often a frame asks
+	return ( Tr2Renderer::GetCurrentFrameCounter() & 1 ) == 0;
+}
+
 uint8_t Tr2ReflectionProbe::GetStartFace() const
 {
 	if( m_renderFrequency == ALL_SIDES_PER_FRAME || !m_onePassDone )

trinity/Tr2ReflectionProbe.h

@@ -20,7 +20,10 @@ BLUE_CLASS( Tr2ReflectionProbe ) :
 	enum ReflectionProbeRenderFrequency
 	{
 		ONE_SIDE_PER_FRAME,
-		ALL_SIDES_PER_FRAME
+		ALL_SIDES_PER_FRAME,
+		// Renders one face and re-filters the cube on every second frame only, so a full
+		// update takes 12 frames. Halves the reflection pass cost for a slower update.
+		ONE_SIDE_EVERY_OTHER_FRAME
 	};
 
 	Tr2ReflectionProbe( IRoot* lockobj = NULL );
@@ -44,6 +47,9 @@ BLUE_CLASS( Tr2ReflectionProbe ) :
 	bool IsHollyWoodModeOn() const;
 	bool ReadyForDynamicObjectReflections() const;
 
+	// False on the frames that ONE_SIDE_EVERY_OTHER_FRAME skips; the render driver then
+	// renders no reflection faces and the last filtered reflection stays in use.
+	bool ShouldRenderThisFrame() const;
 	uint8_t GetStartFace() const;
 	uint8_t GetEndFace() const;
 

trinity/Tr2ReflectionProbe_Blue.cpp

@@ -8,6 +8,7 @@ BLUE_DEFINE( Tr2ReflectionProbe );
 const Be::VarChooser RenderFrequencyChooser[] = {
 	{ "OneSidePerFrame", BeCast( Tr2ReflectionProbe::ONE_SIDE_PER_FRAME ), "One side per frame" },
 	{ "AllSidesPerFrame", BeCast( Tr2ReflectionProbe::ALL_SIDES_PER_FRAME ), "All sides per frame" },
+	{ "OneSideEveryOtherFrame", BeCast( Tr2ReflectionProbe::ONE_SIDE_EVERY_OTHER_FRAME ), "One side every other frame" },
 	{ 0 }
 };