Reintepreting a native array from <Vector3> as <float3>

Could there under any circumstances be an issue with converting
NativeArray<Vector3> vector3Array
using
NativeArray<float3> float3Array = vector3Array.Reinterpret<float3>(UnsafeUtility.SizeOf<Vector3>()); ?

Both Vector3 and float3 are internally stored using three float32, so I can't see any issue... but I'm not too experienced in low level programming, so perhaps on certain platforms it could cause issues, or something like that.

 

You're fine as long as Unity doesn't do something stupid with the layout in the future.

 

That *should* work, in fact you dont need

UnsafeUtility.SizeOf<Vector3>()

in the reinterpret method. Unity already checks the size of both the original and new types against each other and will throw an exception if they do not line up.

That extension method is used as a "safety override" confirming the reinterpret to resize the alignment of the new NativeArray to the new type size.

As both float3 and Vector3 *should* be the same size, you dont need that override.

 

Oh yeah, I do this all the time with no issues. If you reinterpret incompatible types you get garbage data, so it is easy enough to spot bugs. It seems extremely unlikely that Unity would change the float vector layout.

 

Thanks guys.

 

I find simpler to do
var vertices = new NativeArray<Vector3>(mesh.vertices, Allocator.TempJob).Reinterpret<float3>();
where mesh.vertices can by any other vector3[]

 

This copies the data twice - first at the

mesh.vertices

accessor, secondly in the NativeArray constructor. Also, you should probably dispose the NativeArray (not sure if you can do that with the reinterpreted array without storing the original somewhere). But sure, in case of editor code simple solutions are usually better than perfectly optimal code.

 

People are making it sound like this is tentatively safe, but this is pretty much one of the exact situations Reinterpret was made for, so this should be 100% safe unless Unity introduces some crazy bug that would break everything. I'm sure they had this type of conversion in mind when they created float3, and in fact, the reason you can use NativeArray<float3> and NativeArray<Vector3> in Mesh.SetVertices is because they use the underlying unsafe pointer to do pretty much this exact thing in a more direct way.