src/math.lisp @ 5c1a3615e9fc

(in-package #:coding-math)

;; Constants
(defconstant tau (* pi 2))


;; Number range mapping
(defun normalize (min max val)
  (/ (- val min)
     (- max min)))

(defun lerp (from to n)
  "Lerp together `from` and `to` by factor `n`.

  Note that you might want `precise-lerp` instead.

  "
  (+ from
     (* n (- to from))))

(defun precise-lerp (from to n)
  "Lerp together `from` and `to` by factor `n`, precisely.

  Vanilla lerp does not guarantee `(lerp from to 0.0)` will return exactly
  `from` due to floating-point errors.  This version will return exactly `from`
  when given a `n` of `0.0`, at the cost of an extra multiplication.

  "
  (+ (* (- 1 n) from)
     (* n to)))

(defun map-range (source-from source-to dest-from dest-to source-val)
  "Map `source-val` from the source range to the destination range."
  (lerp dest-from dest-to
        (normalize source-from source-to source-val)))