What's the etymology behind type name ID3D10Blob for direct x shaders? - windows

Question

What's the etymology behind type name ID3D10Blob for direct x shaders?
I'm reading http://www.directxtutorial.com/Lesson.aspx?lessonid=11-4-5 and trying to reason about the naming conventions in windows.
I see ID3D10Blob as (I)(D3D10)(Blob).
I = interface?
D3D10 = direct3d 10?
Blob = ?
I've seen "Binary large object" online for Blob, but I'm not sure if that has the same meaning in this context.
What does the blob term mean?

Answer 1

TL;DR: It's just a simple ref-counted container for a variable-length blob of binary data used by the D3DCompiler COM interfaces.
The HLSL compiler produces a 'shader blob' which is just an opaque binary object. It has a size and data. It could be really anything, but in the world of "COM" objects, it was implemented for Windows Vista as ID3D10Blob with the introduction of Direct3D 10.
Historically, Direct3D 9 and earlier had a 'fixed-function' rendering pipeline which means you could use it without HLSL shaders. For Direct3D 10, the 'fixed-function' was removed, so HLSL was required to use it at all. Therefore, a version of the Direct3D HLSL Compiler was added to the OS.
The ID3DBlob interface is what's used for Direct3D 11 or Direct3D 12, but if you look at it closely, it's the same thing.
typedef ID3D10Blob ID3DBlob;
The Direct3D API itself actually doesn't use this specific 'blob' interface. In a C++ STL world, you could use std::vector<uint8_t> as a shader blob:
inline std::vector<uint8_t> ReadData(_In_z_ const wchar_t* name)
{
std::ifstream inFile(name, std::ios::in | std::ios::binary | std::ios::ate);
if (!inFile)
throw std::exception("ReadData");
std::streampos len = inFile.tellg();
if (!inFile)
throw std::exception("ReadData");
std::vector<uint8_t> blob;
blob.resize(size_t(len));
inFile.seekg(0, std::ios::beg);
if (!inFile)
throw std::exception("ReadData");
inFile.read(reinterpret_cast<char*>(blob.data()), len);
if (!inFile)
throw std::exception("ReadData");
inFile.close();
return blob;
}
…
auto vertexShaderBlob = ReadData(L"VertexShader.cso");
ThrowIfFailed(
device->CreateVertexShader(vertexShaderBlob.data(), vertexShaderBlob.size(),
nullptr, m_spVertexShader.ReleaseAndGetAddressOf()));
auto pixelShaderBlob = ReadData(L"PixelShader.cso");
ThrowIfFailed(
device->CreatePixelShader(pixelShaderBlob.data(), pixelShaderBlob.size(),
nullptr, m_spPixelShader.ReleaseAndGetAddressOf()));
See Microsoft Docs and this blog post.