Ease

Namespace: Ava3D

public static class Ease

Shaping a 0..1 parameter, so a move starts and stops instead of switching on and off.

A camera that reaches its mark at the same speed it left is a camera on rails. What the eye reads as deliberate is a move that leans into its start and settles at its end, and that is entirely a matter of what number gets handed to the interpolation — not of the interpolation itself. So there is nothing here that interpolates: float.Lerp and Vector3.Lerp already exist and this reshapes what they are given.

var t = Ease.InOut(elapsed / duration);
camera.LookFrom(Vector3.Lerp(from, to, t), target);

Four functions, and the model closes at four. Ease.Ramp turns a measurement into a 0..1 parameter; Ease.In, Ease.Out and Ease.InOut decide which end of that parameter is soft. The usual libraries carry thirty of these — quad, cubic, quart, expo, elastic, back, bounce, each in three flavours — and the honest reading of that list is that it is a menu of polynomials rather than a set of ideas. The idea is which end has zero slope, and there are only three answers.

Methods

Member	Description
`static float In(float t)`	Soft start, hard stop: away from rest and still accelerating when it arrives. A thing falling, a shot leaving, a cut that wants to feel like an interruption.
`static float InOut(float t)`	Soft at both ends — smoothstep, the same curve GLSL and HLSL have as a built-in. This is the default and it is what most moves want. Zero slope at 0 and at 1 means two of these laid end to end join without a kink, which is what lets a sequence of shots run together as one move rather than as a list of them.
`static float Out(float t)`	Hard start, soft stop: already moving when it begins and settling as it lands. This is the one for a shot that cuts in on a move already under way, and for anything decaying.
`static float Ramp(float from, float to, float value)`	Where `value` falls between `from` and `to`, as 0..1, clamped at both ends. The inverse of `float.Lerp`, which the framework ships and this does not — the map from a range onto 0..1 is the half everybody writes out by hand, usually as `Math.Clamp((x - a) / (b - a), 0, 1)`, and usually more than once in the same file. Composed with `Ease.InOut` it is exactly the three-argument `smoothstep(edge0, edge1, x)` of the shading languages, which is why that is not a fifth function here: `Ease.InOut(Ease.Ramp(0.4f, 0.6f, x))`.