mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-14 05:00:27 +00:00
47 lines
1.5 KiB
Go
47 lines
1.5 KiB
Go
// Copyright (c) 2014 The mathutil Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package mathutil // import "modernc.org/mathutil"
|
|
|
|
import (
|
|
"math"
|
|
)
|
|
|
|
// Approximation type determines approximation methods used by e.g. Envelope.
|
|
type Approximation int
|
|
|
|
// Specific approximation method tags
|
|
const (
|
|
_ Approximation = iota
|
|
Linear // As named
|
|
Sinusoidal // Smooth for all derivations
|
|
)
|
|
|
|
// Envelope is an utility for defining simple curves using a small (usually)
|
|
// set of data points. Envelope returns a value defined by x, points and
|
|
// approximation. The value of x must be in [0,1) otherwise the result is
|
|
// undefined or the function may panic. Points are interpreted as dividing the
|
|
// [0,1) interval in len(points)-1 sections, so len(points) must be > 1 or the
|
|
// function may panic. According to the left and right points closing/adjacent
|
|
// to the section the resulting value is interpolated using the chosen
|
|
// approximation method. Unsupported values of approximation are silently
|
|
// interpreted as 'Linear'.
|
|
func Envelope(x float64, points []float64, approximation Approximation) float64 {
|
|
step := 1 / float64(len(points)-1)
|
|
fslot := math.Floor(x / step)
|
|
mod := x - fslot*step
|
|
slot := int(fslot)
|
|
l, r := points[slot], points[slot+1]
|
|
rmod := mod / step
|
|
switch approximation {
|
|
case Sinusoidal:
|
|
k := (math.Sin(math.Pi*(rmod-0.5)) + 1) / 2
|
|
return l + (r-l)*k
|
|
case Linear:
|
|
fallthrough
|
|
default:
|
|
return l + (r-l)*rmod
|
|
}
|
|
}
|