From c26e0f5923bd44a0356dab8064db3e2fadecd972 Mon Sep 17 00:00:00 2001
From: Preben Eriksen <plemsoft@plemsoft.com>
Date: Thu, 10 Nov 2022 13:41:40 +0100
Subject: [PATCH] PE: DDS - Improve import time if source already has mipmaps
 and are compressed.

---
 .../TextureTool/TextureTool.DirectXTex.cpp    | 27 ++++++++++++++-----
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/Source/Engine/Tools/TextureTool/TextureTool.DirectXTex.cpp b/Source/Engine/Tools/TextureTool/TextureTool.DirectXTex.cpp
index b58dd878a..540c8e186 100644
--- a/Source/Engine/Tools/TextureTool/TextureTool.DirectXTex.cpp
+++ b/Source/Engine/Tools/TextureTool/TextureTool.DirectXTex.cpp
@@ -623,8 +623,21 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
         sliceData.Mips.Resize(mipLevels);
     }
 
+    bool bKeepAsIs = false;
+    if (!options.FlipY &&options.Compress && type == ImageType::DDS && mipLevels == sourceMipLevels && DirectX::IsCompressed(sourceDxgiFormat))
+    {
+        if (!DirectX::IsSRGB(sourceDxgiFormat))
+        {
+            // PE: Keep image in the current compressed format (artist choice) so we dont have to run the slow mipmap generation.
+            // PE: Also converting a BC1 normal map to BC5 will not improve it but just use double gpu mem.
+            bKeepAsIs = true;
+            targetDxgiFormat = sourceDxgiFormat;
+            targetFormat = ToPixelFormat(currentImage->GetMetadata().format);
+        }
+    }
+
     // Decompress if texture is compressed (next steps need decompressed input data, for eg. mip maps generation or format changing)
-    if (DirectX::IsCompressed(sourceDxgiFormat))
+    if (!bKeepAsIs && DirectX::IsCompressed(sourceDxgiFormat))
     {
         auto& tmpImg = GET_TMP_IMG();
 
@@ -640,7 +653,7 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
     }
 
     // Fix sRGB problem
-    if (DirectX::IsSRGB(sourceDxgiFormat))
+    if (!bKeepAsIs && DirectX::IsSRGB(sourceDxgiFormat))
     {
         sourceDxgiFormat = ToDxgiFormat(PixelFormatExtensions::ToNonsRGB(ToPixelFormat(sourceDxgiFormat)));
         ((DirectX::TexMetadata&)currentImage->GetMetadata()).format = sourceDxgiFormat;
@@ -649,7 +662,7 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
     }
 
     // Remove alpha if source texture has it but output should not, valid for compressed output only (DirectX seams to use alpha to pre-multiply colors because BC1 format has no place for alpha)
-    if (DirectX::HasAlpha(sourceDxgiFormat) && options.Type == TextureFormatType::ColorRGB && options.Compress)
+    if (!bKeepAsIs && DirectX::HasAlpha(sourceDxgiFormat) && options.Type == TextureFormatType::ColorRGB && options.Compress)
     {
         auto& tmpImg = GET_TMP_IMG();
 
@@ -674,7 +687,7 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
     }
 
     // Check flip/rotate source image
-    if (options.FlipY)
+    if (!bKeepAsIs && options.FlipY)
     {
         auto& tmpImg = GET_TMP_IMG();
 
@@ -691,7 +704,7 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
     }
 
     // Generate mip maps chain
-    if (useMipLevels && options.GenerateMipMaps)
+    if (!bKeepAsIs && useMipLevels && options.GenerateMipMaps)
     {
         auto& tmpImg = GET_TMP_IMG();
 
@@ -714,7 +727,7 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
     }
 
     // Preserve mipmap alpha coverage (if requested)
-    if (DirectX::HasAlpha(currentImage->GetMetadata().format) && options.PreserveAlphaCoverage && useMipLevels)
+    if (!bKeepAsIs && DirectX::HasAlpha(currentImage->GetMetadata().format) && options.PreserveAlphaCoverage && useMipLevels)
     {
         auto& tmpImg = GET_TMP_IMG();
 
@@ -746,7 +759,7 @@ bool TextureTool::ImportTextureDirectXTex(ImageType type, const StringView& path
     ASSERT((int32)currentImage->GetMetadata().mipLevels >= mipLevels);
 
     // Compress mip maps or convert image
-    if (targetDxgiFormat != sourceDxgiFormat)
+    if (!bKeepAsIs && targetDxgiFormat != sourceDxgiFormat)
     {
         auto& tmpImg = GET_TMP_IMG();