Devil's advocate: does this make a difference in codegen outside of non-optimizing builds (i.e. debug without -Og)? The vector3 constructor is trivial and a candidate for constexpr. Additionally, the zero-argument default constructor initializes a vector3 to zero automatically (to prevent bugs with uninitialized vectors).

On the whole, this is probably better for consistency. It's easier to miss a non-zero constant in the explicit initializer form. One thing I'd like to see is for the matrix4x4fIdentity variables be moved to matrix4x4f::IDENTITY instead.

Final thought: the all-uppercase naming is appropriate for enumeration constants and macros, but as this is neither a macro nor an enum I think vector3f::Zero is more appropriate?

This was initially less about the quality of code gen and was more of a quality of life coding change for me. It was really annoying me seeing all of these calls to vector3f(0.f, 0.f, 0.f) everywhere! I initially changed them to use the default ctor but in some places the code became less readable, so I added the constant ZERO to make them clearer.

I've now done the matrix classes Identity functions making them into a static const and removed the other static const matrix4x4fIdentity like values