Vulkan中KTX1纹理定向的问题

Question

我的Vulkan渲染器在将纹理定向到3d模型时遇到问题。

特别是，我有一个工作版本，该版本加载了bmp图像，并与正常外观的苹果完美融合。然后，我决定使用PVRTexTool生成的纹理编写KTX解析器。我能够加载和映射纹理（验证中没有错误），但方向已关闭。

我曾尝试在导出之前以不同的方式旋转和翻转图像，但是看起来总是一样。任何猜测我在这里做错了吗？

从VK_FORMAT_R8G8B8A8_UNORM / GL_RGBA8UI PVRTexTool加载生成的KTX中加载：

从BMP加载：

PVRTexTool生成的KTX文件的唯一方向输出如下（我无法找到如何更改它的方法：]

KTXOrientation S=r,T=d,R=i

KTX specification描述以下有关方向的信息：

为了帮助编写图像处理工具和查看器，KTX文件中数据的方向可以在文件的键/值元数据。请注意，此元数据仅影响逻辑数据的解释，对像素映射没有影响在文件字节流中进行纹理坐标处理。推荐的钥匙用途是：

KTXorientation

建议查看和编辑工具至少支持以下值：S = r，T = dS = r，T = uS = r，T = d，R = iS = r，T = u，R = o

where

S indicates the direction of increasing S values
T indicates the direction of increasing T values
R indicates the direction of increasing R values
r indicates increasing to the right
l indicates increasing to the left
d indicates increasing downwards
u indicates increasing upwards
o indicates increasing out from the screen (moving towards viewer)
i indicates increasing in towards the screen (moving away from viewer)

KTX解析器的代码：

  type Image_State (Data_Size : Int) is record
      Mipmaps,
      Faces,
      Height,
      Width,
      Format : Int_Unsigned_C;
      Data   : Array_Byte (1..Data_Size);
    end record;
  type Ptr_Image_State is access all Image_State;

  ----------------
  -- Load_Image --
  ----------------

  procedure Load_Image (Path : Str; Image : in out Ptr_Image_State) is

    -- https://www.khronos.org/opengles/sdk/tools/KTX/file_format_spec/
    type KTX_Header_State is record
        Id : Str_8 (1..12) := (others => NULL_CHAR_8);
        Endianness,
        Kind,   
        Kind_Size, 
        GL_Format, 
        Internal_Format, 
        Base_Format,
        Width,      
        Height, 
        Depth,     
        Array_Length, 
        Faces, 
        Mipmaps, 
        Key_Value_Bytes : Int_Unsigned_C := 0;
      end record with Pack;

    Image_Size : Int_Unsigned_C;
    Header     : KTX_Header_State;
    Data       : Ada.Streams.Stream_IO.File_Type; 
    begin
      Open (Data, In_File,
             To_Str_8 (S (OS_Info.App_Path) & "Assets\Textures" & S & Path & ".ktx"));

      -- Load the header and skip to the image data
      KTX_Header_State'Read (Ada.Streams.Stream_IO.Stream (Data), Header);
      Skip (Data, Int (Header.Key_Value_Bytes));
      Int_Unsigned_C'Read (Ada.Streams.Stream_IO.Stream (Data), Image_Size);

      -- Sanity check
      Assert (Header.Id (2..7) = "KTX 11");

      -- Map OpenGL format to Vulkan equivalent and fix up the mipmap count...
      if Header.Mipmaps = 0 then Header.Mipmaps := 1; end if; 
      case Header.Internal_Format is
        when 16#9137# => Header.Internal_Format := -- GL_COMPRESSED_RGBA_PVRTC_2BPPV2_IMG
          VK_FORMAT_PVRTC2_2BPP_UNORM_BLOCK_IMG; 
        when 16#9138# => Header.Internal_Format := -- GL_COMPRESSED_RGBA_PVRTC_4BPPV2_IMG
          VK_FORMAT_PVRTC2_4BPP_UNORM_BLOCK_IMG; 
        when 16#93F0# => Header.Internal_Format := -- GL_COMPRESSED_SRGB_ALPHA_PVRTC_2BPPV2_IMG
          VK_FORMAT_PVRTC2_2BPP_SRGB_BLOCK_IMG;  
        when 16#93F1# => Header.Internal_Format := -- GL_COMPRESSED_SRGB_ALPHA_PVRTC_4BPPV2_IMG
          VK_FORMAT_PVRTC2_4BPP_SRGB_BLOCK_IMG;  
        when 16#8D7C# => Header.Internal_Format := -- GL_RGBA8UI
          VK_FORMAT_R8G8B8A8_UNORM;              
        when others   => raise Unsupported_Compression_Format with Header.Internal_Format'Image;
      end case;

      -- Load the image in a single go - no reason for special loops...
      Image := new Image_State (Int (Image_Size),
                                Header.Mipmaps,
                                Header.Faces,
                                Header.Width,
                                Header.Height,
                                Header.Internal_Format, others => <>);
      Array_Byte'Read (Ada.Streams.Stream_IO.Stream (Data), Image.Data);   

      Close (Data);
    end;

Answer 1

如果我没看错文档，那么KTXorientation键/值对将存储在您在代码中跳过的数据中

Skip (Data, Int (Header.Key_Value_Bytes));

第2.14节keyAndValue描述了该节的格式