Static SCNPreferredRenderingAPIKey 

pub unsafe static SCNPreferredRenderingAPIKey: &'static SCNViewOption

Available on crate feature SCNView only.

Pass it as the key in the options dictionary given to initWithFrame:options:. The value is a NSNumber wrapping a SCNRenderingAPI. You can also select the preferred rendering API directly from the SCNView inspector in InterfaceBuilder.

See also Apple’s documentation