Trait crystalorb::world::DisplayState

pub trait DisplayState: Send + Sync + Clone + Debug {
    fn from_interpolation(state1: &Self, state2: &Self, t: f64) -> Self;
}

The DisplayState represents the information about how to display the World at its current state. For example, while a World might contain information about player’s position and velocities, some games may only need to know about the position to render it (unless you’re doing some fancy motion-blur). You can think of a DisplayState as the “output” of a World. There is nothing stopping you from making the DisplayState the same structure as the World if it makes more sense for your game, but most of the time, the World structure may contain things that are inefficient to copy around (e.g. an entire physics engine)

Required methods

fn from_interpolation(state1: &Self, state2: &Self, t: f64) -> Self

CrystalOrb needs to mix different DisplayStates from different Worlds together, as well as mix DisplayState from two adjacent timestamps. The from_interpolation method tells CrystalOrb how to perform this “mix” operation. Here, the t parameter is the interpolation parameter that ranges between 0.0 and 1.0, where t = 0.0 represents the request to have 100% of state1 and 0% of state2, and where t = 1.0 represents the request to have 0% of state1 and 100% of state2.

A common operation to implement this function is through linear interpolation, which looks like this:

state1 * (1.0 - t) + state2 * t

However, for things involving rotation, you may need to use spherical linear interpolation, or circular statistics, and perhaps you may need to convert between coordinate systems before/after performing the interpolation to get the right transformations about the correct pivot points.

Implementors

impl<T: DisplayState> DisplayState for Timestamped<T>

fn from_interpolation(state1: &Self, state2: &Self, t: f64) -> Self

Interpolate between two timestamped display states. If the two timestamps are different, then the interpolation parameter t must be either 0.0 or 1.0.

Panics

Panics if the timestamps are different but the interpolation parameter is not 0.0 nor 1.0, since timestamps are whole number values and cannot be continuously interpolated. Interpolating between two display states of different timestamps is known as “tweening” (i.e. animation in-betweening) and should be done using Tweened::from_interpolation.