> On Nov 3, 2017, at 3:33 PM, Kelvin Ma <kelvin1...@gmail.com> wrote:
>
>
>
> On Fri, Nov 3, 2017 at 2:05 PM, Steve Canon via swift-evolution
> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
> If/when 16b floats were added to the standard lib, you would just write:
>
> let vertexData: [Float16] = [ 1, 0, 0.5, 1 ]
>
> I should note that something like vertex coordinates is usually better
> modeled with a more specific type than [Float], like SCNVector4 or
> simd.float4 or your own type, which also solves this problem:
>
> import SceneKit
> let vertexData = SCNVector4(1, 0, 0.5, 1)
>
> import simd
> let vertexData = float4(1, 0, 0.5, 1)
>
> (NB both of these frameworks are Apple-specific).
>
> - Steve
>
> Sent from my iPhone
>
> If @_fixed_layout was supported this would be sensible, but most graphics
> frameworks expect a plain buffer of floats and the packing order is implicit.
> We can’t model vertex vectors with Swift structs because we can’t safely
> pointer-cast them to an array of floats.
SCNVector4 is a C struct and hence has fixed layout. simd.float4 fixes its
ordering by having a single field that is an LLVM ext-vector type. Both can be
safely converted to a buffer of floats.
– Steve
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