MaterialCacheVirtualTextureDescriptor.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Math/UnrealMath.h"
#include "NaniteDefinitions.h"
#include "TextureResource.h"
#include "VirtualTexturing.h"
 
class FTextureResource;
 
struct UMaterialCacheVirtualTextureDescriptor
{
    operator FUintVector2() const
    {
        FUintVector2 Out;
        FMemory::Memcpy(&Out, this, sizeof(FUintVector2));
        return Out;
    }
    
    // DWord0
    uint32_t PageX : 12;
    uint32_t PageY : 12;
    uint32_t PageTableMipBias : 4;
    uint32_t SpaceID : 4;
 
    // DWord1
    uint32_t WidthInPages : 12;
    uint32_t HeightInPages : 12;
    uint32_t MaxLevel : 6;
    uint32_t UVCoordinateIndex : 2;
};
 
inline UMaterialCacheVirtualTextureDescriptor PackMaterialCacheTextureDescriptor(FTextureResource* Resource, uint32_t UVCoordinateIndex) 
{
    checkf(UVCoordinateIndex <= 3 && UVCoordinateIndex < NANITE_MAX_UVS, TEXT("Out of bounds coordinate index, consider expanding bit-width of UVCoordinateIndex"));
 
    UMaterialCacheVirtualTextureDescriptor Descriptor{};
    if (!Resource)
    {
        return Descriptor;
    }
 
    FVirtualTexture2DResource* VirtualResource = Resource->GetVirtualTexture2DResource();
    if (!ensure(VirtualResource))
    {
        return Descriptor;
    }
 
    IAllocatedVirtualTexture* Allocation = VirtualResource->GetAllocatedVT();
    if (!ensure(Allocation))
    {
        return Descriptor;
    }
    
    Descriptor.PageX             = Allocation->GetVirtualPageX();
    Descriptor.PageY             = Allocation->GetVirtualPageY();
    Descriptor.WidthInPages      = Allocation->GetWidthInTiles();
    Descriptor.HeightInPages     = Allocation->GetHeightInTiles();
    Descriptor.PageTableMipBias  = FMath::FloorLog2(Allocation->GetVirtualTileSize());
    Descriptor.SpaceID           = Allocation->GetSpaceID();
    Descriptor.MaxLevel          = Allocation->GetMaxLevel();
    Descriptor.UVCoordinateIndex = UVCoordinateIndex;
    return Descriptor;
}
 
static_assert(sizeof(UMaterialCacheVirtualTextureDescriptor) == sizeof(FUintVector2), "Unexpected descriptor size");