Struct fidl_fuchsia_ui_gfx::SetCameraPoseBufferCmd

#[repr(C)]
pub struct SetCameraPoseBufferCmd {
    pub camera_id: u32,
    pub buffer_id: u32,
    pub num_entries: u32,
    pub base_time: i64,
    pub time_interval: u64,
}

Sets the “pose buffer” for the camera identified by camera_id. This operation can be applied to both Cameras and StereoCameras.

This will override any position and rotation set for the camera and will make it take its position and rotation from the pose buffer each frame based on the presentation time for that frame.

A pose buffer represents a ring buffer of poses for a fixed number of time points in the future. Each entry in the buffer identified by buffer_id is a quaternion and a position layed out as follows:

struct Pose { // Quaternion float32 a; float32 b; float32 c; float32 d;

// Position float32 x; float32 y; float32 z;

// Reserved/Padding byte[4] reserved; }

The buffer can be thought of as a packed array of num_entries Pose structs and is required to be at least num_entries * sizeof(Pose) bytes.

The quaternions and positions are specified in the space of the camera’s parent node.

base_time is a base time point expressed in nanoseconds in the CLOCK_MONOTONIC timebase and time_interval is the time in nanoseconds between entries in the buffer. base_time must be in the past.

For a given point in time t expressed in nanoseconds in the CLOCK_MONOTONIC timebase the index of the corresponding pose in the pose buffer can be computed as follows:

index(t) = ((t - base_time) / time_interval) % num_entries

poses[index(t)] is valid for t over the time interval (t - time_interval, t] and should be expected to updated continuously without synchronization for the duration of that interval. If a single pose value is needed for multiple non-atomic operations a value should be latched and stored outside the pose buffer.

Because the poses are not protected by any synchronization primitives it is possible that when a pose is latched it will be only partially updated, and the pose being read will contain some components from the pose before it is updated and some components from the updated pose. The safety of using these “torn” poses relies on two things:

1. Sequential poses written to poses[index(t)] are very similar to each other numerically, so that if some components are taken from the first and some are taken from another the result is numerically similar to both

2. The space of positions and quaternions is locally flat at the scale of changes between sequential updates, which guarantees that two poses which are numerically similar also represent semantically similar poses (i.e. there are no discontinuities which will cause a small numerical change in the position or quaterninon to cause a large change in the encoded pose) For positions this is guaranteed because Scenic uses a Euclidean 3-space which is globally flat and for quaternions this is guaranteed because quaternions encode rotation as points on a unit 4-sphere, and spheres are locally flat. For more details on the encoding of rotations in quaterions see https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation

This commanderation is intended for late latching camera pose to support low-latency motion-tracked rendering.

Fields

camera_id: u32

buffer_id: u32

num_entries: u32

base_time: i64

time_interval: u64

Trait Implementations

impl Clone for SetCameraPoseBufferCmd

fn clone(&self) -> SetCameraPoseBufferCmd

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SetCameraPoseBufferCmd

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Decode<SetCameraPoseBufferCmd> for SetCameraPoseBufferCmd

fn new_empty() -> Self

Creates a valid instance of Self. The specific value does not matter, since it will be overwritten by decode.

unsafe fn decode( &mut self, decoder: &mut Decoder<'_>, offset: usize, _depth: Depth ) -> Result<()>

Decodes an object of type T from the decoder’s buffers into self.

impl Encode<SetCameraPoseBufferCmd> for &SetCameraPoseBufferCmd

unsafe fn encode( self, encoder: &mut Encoder<'_>, offset: usize, _depth: Depth ) -> Result<()>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID.

impl<T0: Encode<u32>, T1: Encode<u32>, T2: Encode<u32>, T3: Encode<i64>, T4: Encode<u64>> Encode<SetCameraPoseBufferCmd> for (T0, T1, T2, T3, T4)

unsafe fn encode( self, encoder: &mut Encoder<'_>, offset: usize, depth: Depth ) -> Result<()>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID.

impl Hash for SetCameraPoseBufferCmd

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for SetCameraPoseBufferCmd

fn cmp(&self, other: &SetCameraPoseBufferCmd) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for SetCameraPoseBufferCmd

fn eq(&self, other: &SetCameraPoseBufferCmd) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for SetCameraPoseBufferCmd

fn partial_cmp(&self, other: &SetCameraPoseBufferCmd) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl TypeMarker for SetCameraPoseBufferCmd

type Owned = SetCameraPoseBufferCmd

The owned Rust type which this FIDL type decodes into.

fn inline_align(_context: Context) -> usize

Returns the minimum required alignment of the inline portion of the encoded object. It must be a (nonzero) power of two.

fn inline_size(_context: Context) -> usize

Returns the size of the inline portion of the encoded object, including padding for alignment. Must be a multiple of inline_align.

fn encode_is_copy() -> bool

Returns true if the memory layout of Self::Owned matches the FIDL wire format and encoding requires no validation. When true, we can optimize encoding arrays and vectors of Self::Owned to a single memcpy.

fn decode_is_copy() -> bool

Returns true if the memory layout of Self::Owned matches the FIDL wire format and decoding requires no validation. When true, we can optimize decoding arrays and vectors of Self::Owned to a single memcpy.

impl ValueTypeMarker for SetCameraPoseBufferCmd

type Borrowed<'a> = &'a SetCameraPoseBufferCmd

The Rust type to use for encoding. This is a particular Encode<Self> type cheaply obtainable from &Self::Owned. There are three cases:

fn borrow<'a>(value: &'a <Self as TypeMarker>::Owned) -> Self::Borrowed<'a>

Cheaply converts from &Self::Owned to Self::Borrowed.

impl Copy for SetCameraPoseBufferCmd

impl Eq for SetCameraPoseBufferCmd

impl Persistable for SetCameraPoseBufferCmd

impl StructuralPartialEq for SetCameraPoseBufferCmd