// Copyright Epic Games, Inc. All Rights Reserved.

/*=============================================================================
	SkyPassRendering.cpp: Sky pass rendering implementation.
=============================================================================*/

#include "SkyPassRendering.h"
#include "BasePassRendering.h"
#include "MobileBasePassRendering.h"
#include "DeferredShadingRenderer.h"
#include "ScenePrivate.h"
#include "SceneRendering.h"
#include "MeshPassProcessor.inl"



FSkyPassMeshProcessor::FSkyPassMeshProcessor(const FScene* Scene, const FSceneView* InViewIfDynamicMeshCommand, const FMeshPassProcessorRenderState& InPassDrawRenderState, FMeshPassDrawListContext* InDrawListContext)
	: FMeshPassProcessor(Scene, Scene->GetFeatureLevel(), InViewIfDynamicMeshCommand, InDrawListContext)
	, PassDrawRenderState(InPassDrawRenderState)
{
}

void FSkyPassMeshProcessor::AddMeshBatch(const FMeshBatch& RESTRICT MeshBatch, uint64 BatchElementMask, const FPrimitiveSceneProxy* RESTRICT PrimitiveSceneProxy, int32 StaticMeshId)
{
	const FMaterialRenderProxy* MaterialRenderProxy = MeshBatch.MaterialRenderProxy;
	while (MaterialRenderProxy)
	{
		const FMaterial* Material = MaterialRenderProxy->GetMaterialNoFallback(FeatureLevel);
		if (Material && Material->IsSky())
		{
			if (TryAddMeshBatch(MeshBatch, BatchElementMask, PrimitiveSceneProxy, StaticMeshId, *MaterialRenderProxy, *Material))
			{
				break;
			}
		}

		MaterialRenderProxy = MaterialRenderProxy->GetFallback(FeatureLevel);
	}
}

bool FSkyPassMeshProcessor::TryAddMeshBatch(
	const FMeshBatch& RESTRICT MeshBatch,
	uint64 BatchElementMask,
	const FPrimitiveSceneProxy* RESTRICT PrimitiveSceneProxy,
	int32 StaticMeshId,
	const FMaterialRenderProxy& MaterialRenderProxy,
	const FMaterial& Material)
{
	const FMeshDrawingPolicyOverrideSettings OverrideSettings = ComputeMeshOverrideSettings(MeshBatch);
	const ERasterizerFillMode MeshFillMode = ComputeMeshFillMode(MeshBatch, Material, OverrideSettings);
	const ERasterizerCullMode MeshCullMode = ComputeMeshCullMode(MeshBatch, Material, OverrideSettings);
	return Process(MeshBatch, BatchElementMask, PrimitiveSceneProxy, StaticMeshId, MaterialRenderProxy, Material, MeshFillMode, MeshCullMode);
}

bool FSkyPassMeshProcessor::Process(
	const FMeshBatch& MeshBatch,
	uint64 BatchElementMask,
	const FPrimitiveSceneProxy* RESTRICT PrimitiveSceneProxy,
	int32 StaticMeshId,
	const FMaterialRenderProxy& RESTRICT MaterialRenderProxy,
	const FMaterial& RESTRICT MaterialResource,
	ERasterizerFillMode MeshFillMode,
	ERasterizerCullMode MeshCullMode)
{
	typedef FUniformLightMapPolicy LightMapPolicyType;
	FUniformLightMapPolicy NoLightmapPolicy(LMP_NO_LIGHTMAP);
	const FVertexFactory* VertexFactory = MeshBatch.VertexFactory;

	if (Scene->GetShadingPath()==EShadingPath::Deferred)
	{
		TMeshProcessorShaders<
			TBasePassVertexShaderPolicyParamType<LightMapPolicyType>,
			TBasePassPixelShaderPolicyParamType<LightMapPolicyType>> SkyPassShaders;

		const bool bRenderSkylight = false;
		if (!GetBasePassShaders<LightMapPolicyType>(
			MaterialResource,
			VertexFactory->GetType(),
			NoLightmapPolicy,
			FeatureLevel,
			bRenderSkylight,
			false,
			&SkyPassShaders.VertexShader,
			&SkyPassShaders.PixelShader
			))
		{
			return false;
		}

		TBasePassShaderElementData<LightMapPolicyType> ShaderElementData(nullptr);
		ShaderElementData.InitializeMeshMaterialData(ViewIfDynamicMeshCommand, PrimitiveSceneProxy, MeshBatch, StaticMeshId, false);

		const FMeshDrawCommandSortKey SortKey = CalculateMeshStaticSortKey(SkyPassShaders.VertexShader, SkyPassShaders.PixelShader);

		BuildMeshDrawCommands(
			MeshBatch,
			BatchElementMask,
			PrimitiveSceneProxy,
			MaterialRenderProxy,
			MaterialResource,
			PassDrawRenderState,
			SkyPassShaders,
			MeshFillMode,
			MeshCullMode,
			SortKey,
			EMeshPassFeatures::Default,
			ShaderElementData);
	}
	else
	{
		TMeshProcessorShaders<
			TMobileBasePassVSPolicyParamType<LightMapPolicyType>,
			TMobileBasePassPSPolicyParamType<LightMapPolicyType>> SkyPassShaders;

		if (!MobileBasePass::GetShaders(
			LMP_NO_LIGHTMAP,
			0,
			MaterialResource,
			VertexFactory->GetType(),
			false,
			SkyPassShaders.VertexShader,
			SkyPassShaders.PixelShader
		))
		{
			return false;
		}

		// Mask sky pixels so we can skip them when rendering per-pixel fog
		PassDrawRenderState.SetDepthStencilState(TStaticDepthStencilState<
			false, CF_DepthNearOrEqual,
			true, CF_Always, SO_Keep, SO_Keep, SO_Replace,
			false, CF_Always, SO_Keep, SO_Keep, SO_Keep,
			0x00, STENCIL_MOBILE_SKY_MASK>::GetRHI());
		
		PassDrawRenderState.SetStencilRef(1); 
		
		TMobileBasePassShaderElementData<LightMapPolicyType> ShaderElementData(nullptr, false);
		ShaderElementData.InitializeMeshMaterialData(ViewIfDynamicMeshCommand, PrimitiveSceneProxy, MeshBatch, StaticMeshId, false);

		const FMeshDrawCommandSortKey SortKey = CalculateMeshStaticSortKey(SkyPassShaders.VertexShader, SkyPassShaders.PixelShader);

		BuildMeshDrawCommands(
			MeshBatch,
			BatchElementMask,
			PrimitiveSceneProxy,
			MaterialRenderProxy,
			MaterialResource,
			PassDrawRenderState,
			SkyPassShaders,
			MeshFillMode,
			MeshCullMode,
			SortKey,
			EMeshPassFeatures::Default,
			ShaderElementData);
	}

	return true;
}

FMeshPassProcessor* CreateSkyPassProcessor(const FScene* Scene, const FSceneView* InViewIfDynamicMeshCommand, FMeshPassDrawListContext* InDrawListContext)
{
	FMeshPassProcessorRenderState DrawRenderState;
	FExclusiveDepthStencil::Type BasePassDepthStencilAccess_NoDepthWrite = FExclusiveDepthStencil::Type(Scene->DefaultBasePassDepthStencilAccess & ~FExclusiveDepthStencil::DepthWrite);
	SetupBasePassState(BasePassDepthStencilAccess_NoDepthWrite, false, DrawRenderState);

	return new(FMemStack::Get()) FSkyPassMeshProcessor(Scene, InViewIfDynamicMeshCommand, DrawRenderState, InDrawListContext);
}

FRegisterPassProcessorCreateFunction RegisterSkyPass(&CreateSkyPassProcessor, EShadingPath::Deferred, EMeshPass::SkyPass, EMeshPassFlags::MainView);
FRegisterPassProcessorCreateFunction RegisterMobileSkyPass(&CreateSkyPassProcessor, EShadingPath::Mobile, EMeshPass::SkyPass, EMeshPassFlags::MainView);