A bitmask that determines from which bits that stencil comparison tests can read.
- iOS 8.0+
- macOS 10.11+
- tvOS 9.0+
readMask bits are used for logical AND operations to both the stored stencil value and the reference value.
The least significant bits of the read mask are used. The default value is all ones. A logical AND operation with the default
readMask does not change the value.
Specifying Stencil Bit Mask Properties