EM_Task/UnrealEd/Private/ThumbnailRendering/TextureThumbnailRenderer.cpp

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

#include "ThumbnailRendering/TextureThumbnailRenderer.h"
#include "CanvasItem.h"
#include "Engine/Engine.h"
#include "Engine/Texture.h"
#include "Engine/Texture2D.h"
#include "Engine/TextureLightProfile.h"
#include "ThumbnailRendering/ThumbnailManager.h"
#include "EngineGlobals.h"
#include "Engine/TextureCube.h"
#include "Engine/Texture2DArray.h"
#include "Texture2DPreview.h"
#include "Engine/TextureRenderTargetCube.h"

#include "CubemapUnwrapUtils.h"
#include "NormalMapPreview.h"
#include "CanvasTypes.h"

UTextureThumbnailRenderer::UTextureThumbnailRenderer(const FObjectInitializer& ObjectInitializer)
    : Super(ObjectInitializer)
{
}

void UTextureThumbnailRenderer::GetThumbnailSize(UObject* Object, float Zoom, uint32& OutWidth, uint32& OutHeight) const
{
    UTexture* Texture                         = Cast<UTexture>(Object);
    UTextureLightProfile* TextureLightProfile = Cast<UTextureLightProfile>(Object);

    if (TextureLightProfile)
    {
        // otherwise a 1D texture would result in a very boring thumbnail
        OutWidth  = 192;
        OutHeight = 192;
        return;
    }

    if (Texture != nullptr)
    {
        OutWidth  = FMath::TruncToInt(Zoom * (float)Texture->GetSurfaceWidth());
        OutHeight = FMath::TruncToInt(Zoom * (float)Texture->GetSurfaceHeight());
    }
    else
    {
        OutWidth = OutHeight = 0;
    }
}

void UTextureThumbnailRenderer::Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height, FRenderTarget*, FCanvas* Canvas, bool bAdditionalViewFamily)
{
    UTexture* Texture = Cast<UTexture>(Object);
    if (Texture != nullptr && Texture->Resource != nullptr)
    {
        UTexture2D* Texture2D = Cast<UTexture2D>(Texture);

        // Take the alpha channel into account for textures that have one.
        // This provides a much better preview than just showing RGB,
        // Because the RGB content in areas with an alpha of 0 is often garbage that will not be seen in normal conditions.
        // Non-UI textures often have uncorrelated data in the alpha channel (like a skin mask, specular power, etc) so we only preview UI textures this way.
        const bool bUseTranslucentBlend           = Texture2D && Texture2D->HasAlphaChannel() && ((Texture2D->LODGroup == TEXTUREGROUP_UI) || (Texture2D->LODGroup == TEXTUREGROUP_Pixels2D));

        UTextureCube* TextureCube                 = Cast<UTextureCube>(Texture);
        UTexture2DArray* Texture2DArray           = Cast<UTexture2DArray>(Texture);
        UTextureRenderTargetCube* RTTextureCube   = Cast<UTextureRenderTargetCube>(Texture);
        UTextureLightProfile* TextureLightProfile = Cast<UTextureLightProfile>(Texture);
        const bool bIsVirtualTexture              = Texture->IsCurrentlyVirtualTextured();

        TRefCountPtr<FBatchedElementParameters> BatchedElementParameters;

        if (TextureCube || RTTextureCube)
        {
            // is released by the render thread when it was rendered
            BatchedElementParameters = new FMipLevelBatchedElementParameters((float)0);

            // If the thumbnail is square then make it 2:1 for cubes.
            if (Width == Height)
            {
                Height = Width / 2;
                Y += Height / 2;
            }
        }
        else if (Texture2DArray)
        {
            bool bIsNormalMap        = Texture2DArray->IsNormalMap();
            bool bIsSingleChannel    = true;
            BatchedElementParameters = new FBatchedElementTexture2DPreviewParameters(0, 0, bIsNormalMap, bIsSingleChannel, false, false, true);
        }
        else if (TextureLightProfile)
        {
            BatchedElementParameters = new FIESLightProfileBatchedElementParameters(TextureLightProfile->Brightness);
        }
        else if (Texture2D && Texture2D->IsNormalMap())
        {
            BatchedElementParameters = new FNormalMapBatchedElementParameters();
        }

        if (bUseTranslucentBlend)
        {
            // If using alpha, draw a checkerboard underneath first.
            const int32 CheckerDensity = 8;
            auto* Checker              = UThumbnailManager::Get().CheckerboardTexture;
            Canvas->DrawTile(
                0.0f, 0.0f, Width, Height,                   // Dimensions
                0.0f, 0.0f, CheckerDensity, CheckerDensity,  // UVs
                FLinearColor::White, Checker->Resource);     // Tint & Texture
        }

        // Use A canvas tile item to draw
        FCanvasTileItem CanvasTile(FVector2D(X, Y), Texture->Resource, FVector2D(Width, Height), FLinearColor::White);
        CanvasTile.BlendMode                = bUseTranslucentBlend ? SE_BLEND_Translucent : SE_BLEND_Opaque;
        CanvasTile.BatchedElementParameters = BatchedElementParameters;
        if (bIsVirtualTexture && Texture->Source.GetNumBlocks() > 1)
        {
            // Adjust UVs to display entire UDIM range, acounting for UE4 inverted V-axis
            // We're not actually rendering a VT here, but the editor-only texture we're using is still using the UDIM tile layout
            // So we use inverted Y-axis, but then normalize back to [0,1)
            const FIntPoint BlockSize = Texture->Source.GetSizeInBlocks();
            const float RcpBlockSizeY = 1.0f / (float)BlockSize.Y;
            CanvasTile.UV0.Y          = (1.0f - (float)BlockSize.Y) * RcpBlockSizeY;
            CanvasTile.UV1.Y          = RcpBlockSizeY;
        }
        CanvasTile.Draw(Canvas);

        if (TextureLightProfile)
        {
            float Brightness = TextureLightProfile->Brightness;

            // Brightness in Lumens
            FText BrightnessText = FText::AsNumber(Brightness);
            FCanvasTextItem TextItem(FVector2D(5.0f, 5.0f), BrightnessText, GEngine->GetLargeFont(), FLinearColor::White);
            TextItem.EnableShadow(FLinearColor::Black);
            TextItem.Scale = FVector2D(Width / 128.0f, Height / 128.0f);
            TextItem.Draw(Canvas);
        }

        if (bIsVirtualTexture)
        {
            auto VTChars   = TEXT("VT");
            int32 VTWidth  = 0;
            int32 VTHeight = 0;
            StringSize(GEngine->GetLargeFont(), VTWidth, VTHeight, VTChars);
            float PaddingX = Width / 128.0f;
            float PaddingY = Height / 128.0f;
            float ScaleX   = Width / 64.0f;  // Text is 1/64'th of the size of the thumbnails
            float ScaleY   = Height / 64.0f;
            // VT overlay
            FCanvasTextItem TextItem(FVector2D(Width - PaddingX - VTWidth * ScaleX, Height - PaddingY - VTHeight * ScaleY), FText::FromString(VTChars), GEngine->GetLargeFont(), FLinearColor::White);
            TextItem.EnableShadow(FLinearColor::Black);
            TextItem.Scale = FVector2D(ScaleX, ScaleY);
            TextItem.Draw(Canvas);
        }
    }
}