vulkan: Fix multipass RTT in OIT mode

Use correct temp attachment depending on pass count. Keep attachment
index to bind the correct one before final subpass.
Use correct initial layout for OP+PT attachment 1 (was eUndefined) when
creating the RTT render pass.
Fixes Alone in the Dark cutscenes.
Issue #1609

Recreate RTT attachments if switching CopyToVRAM on/off.

core/rend/vulkan/oit/oit_drawer.cpp

@@ -264,9 +264,14 @@ void OITDrawer::UploadMainBuffer(const OITDescriptorSets::VertexShaderUniforms&
 vk::Framebuffer OITTextureDrawer::getFramebuffer(int renderPass, int renderPassCount)
 {
 	if (renderPass < renderPassCount - 1)
-		return *tempFramebuffers[(renderPassCount - 1 - renderPass) % 2];
-	else
+	{
+		framebufferIndex = (renderPassCount - renderPass) % 2;
+		return *tempFramebuffers[framebufferIndex];
+	}
+	else {
+		framebufferIndex = 0;
 		return *framebuffer;
+	}
 }
 
 bool OITDrawer::Draw(const Texture *fogTexture, const Texture *paletteTexture)
@@ -467,10 +472,11 @@ void OITDrawer::MakeBuffers(int width, int height, vk::ImageUsageFlags colorUsag
 {
 	oitBuffers->Init(width, height);
 
-	if (width <= maxWidth && height <= maxHeight)
+	if (width <= maxWidth && height <= maxHeight && colorUsage == currentBufferUsage)
 		return;
 	maxWidth = std::max(maxWidth, width);
 	maxHeight = std::max(maxHeight, height);
+	currentBufferUsage = colorUsage;
 
 	for (auto& framebuffer : tempFramebuffers) {
 		if (framebuffer)

core/rend/vulkan/oit/oit_drawer.h

@@ -82,7 +82,7 @@ class OITDrawer : public BaseDrawer
 
 	void MakeBuffers(int width, int height, vk::ImageUsageFlags colorUsage = {});
 	virtual vk::Framebuffer getFramebuffer(int renderPass, int renderPassCount) = 0;
-	virtual int getFramebufferIndex() { return 0; }
+	int getFramebufferIndex() { return framebufferIndex; }
 
 	vk::Rect2D viewport;
 	std::array<std::unique_ptr<FramebufferAttachment>, 2> colorAttachments;
@@ -92,6 +92,7 @@ class OITDrawer : public BaseDrawer
 	std::vector<bool> clearNeeded;
 	int maxWidth = 0;
 	int maxHeight = 0;
+	int framebufferIndex = 0;
 
 private:
 	void DrawPoly(const vk::CommandBuffer& cmdBuffer, u32 listType, bool autosort, Pass pass,
@@ -128,6 +129,7 @@ class OITDrawer : public BaseDrawer
 	OITDescriptorSets descriptorSets;
 	vk::Buffer curMainBuffer;
 	bool dithering = false;
+	vk::ImageUsageFlags currentBufferUsage {};
 };
 
 class OITScreenDrawer : public OITDrawer
@@ -186,7 +188,6 @@ class OITScreenDrawer : public OITDrawer
 
 protected:
 	vk::Framebuffer getFramebuffer(int renderPass, int renderPassCount) override;
-	int getFramebufferIndex() override { return framebufferIndex; }
 
 private:
 	void MakeFramebuffers(const vk::Extent2D& viewport);
@@ -195,7 +196,6 @@ class OITScreenDrawer : public OITDrawer
 	bool frameRendered = false;
 	float aspectRatio = 0.f;
 	bool frameStarted = false;
-	int framebufferIndex = 0;
 };
 
 class OITTextureDrawer : public OITDrawer

core/rend/vulkan/oit/oit_renderpass.cpp

@@ -31,7 +31,7 @@ vk::UniqueRenderPass RenderPasses::MakeRenderPass(bool initial, bool last, bool
 					initial ? vk::AttachmentLoadOp::eClear : vk::AttachmentLoadOp::eLoad,
 					last ? vk::AttachmentStoreOp::eDontCare : vk::AttachmentStoreOp::eStore,
 					vk::AttachmentLoadOp::eDontCare, vk::AttachmentStoreOp::eDontCare,
-					initial ? vk::ImageLayout::eUndefined : attach0.initialLayout, attach0.finalLayout),
+					initial ? vk::ImageLayout::eUndefined : attach0.finalLayout, attach0.finalLayout), // initial layout is eUndefined for rtt, so use final layout instead
 			// OP+PT depth attachment
 			vk::AttachmentDescription(vk::AttachmentDescriptionFlags(), GetContext()->GetDepthFormat(), vk::SampleCountFlagBits::e1,
 					initial ? vk::AttachmentLoadOp::eClear : vk::AttachmentLoadOp::eLoad,