From 1459fc5be967f26800d0495d9b0676235f8ea9bf Mon Sep 17 00:00:00 2001
From: minjaesong <alswo9628@gmail.com>
Date: Tue, 21 Nov 2023 11:59:58 +0900
Subject: [PATCH] put lin-log scale conversion into separate functions

---
 src/net/torvald/terrarum/audio/AudioMixer.kt  | 28 +++++++++++--------
 .../terrarum/ui/BasicDebugInfoWindow.kt       |  6 +---
 2 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/src/net/torvald/terrarum/audio/AudioMixer.kt b/src/net/torvald/terrarum/audio/AudioMixer.kt
index 94ef6aaaa..9ca933614 100644
--- a/src/net/torvald/terrarum/audio/AudioMixer.kt
+++ b/src/net/torvald/terrarum/audio/AudioMixer.kt
@@ -187,14 +187,9 @@ object AudioMixer: Disposable {
 
         if (lpOutFired) {
             lpAkku += delta
-            // https://www.desmos.com/calculator/dmhve2awxm
-            val t = (lpAkku / lpLength).coerceIn(0.0, 1.0)
-            val b = ln(lpStart / lpTarget) / -1.0
-            val a = lpStart
-            val cutoff = a * exp(b * t)
+            val cutoff = linPercToLog(lpAkku / lpLength, lpStart, lpTarget)
             (fadeBus.filters[0] as Lowpass).setCutoff(cutoff)
 
-
             if (lpAkku >= lpLength) {
                 lpOutFired = false
                 (fadeBus.filters[0] as Lowpass).setCutoff(lpTarget)
@@ -202,11 +197,7 @@ object AudioMixer: Disposable {
         }
         else if (lpInFired) {
             lpAkku += delta
-            // https://www.desmos.com/calculator/dmhve2awxm
-            val t = (lpAkku / lpLength).coerceIn(0.0, 1.0)
-            val b = ln(lpStart / lpTarget) / -1.0
-            val a = lpStart
-            val cutoff = a * exp(b * t)
+            val cutoff = linPercToLog(lpAkku / lpLength, lpStart, lpTarget)
             (fadeBus.filters[0] as Lowpass).setCutoff(cutoff)
 
             if (lpAkku >= lpLength) {
@@ -304,4 +295,19 @@ object AudioMixer: Disposable {
         tracks.forEach { it.tryDispose() }
         masterTrack.tryDispose()
     }
+}
+
+fun linToLogPerc(value: Double, low: Double, high: Double): Double {
+    // https://www.desmos.com/calculator/dmhve2awxm
+    val b = -ln(low / high)
+    val a = low
+    return ln(value / a) / b
+}
+
+fun linPercToLog(perc: Double, low: Double, high: Double): Double {
+    // https://www.desmos.com/calculator/dmhve2awxm
+    val t = perc.coerceIn(0.0, 1.0)
+    val b = -ln(low / high)
+    val a = low
+    return a * exp(b * t)
 }
\ No newline at end of file
diff --git a/src/net/torvald/terrarum/ui/BasicDebugInfoWindow.kt b/src/net/torvald/terrarum/ui/BasicDebugInfoWindow.kt
index c56a5cf44..b130016bd 100644
--- a/src/net/torvald/terrarum/ui/BasicDebugInfoWindow.kt
+++ b/src/net/torvald/terrarum/ui/BasicDebugInfoWindow.kt
@@ -555,11 +555,7 @@ class BasicDebugInfoWindow : UICanvas() {
     private fun drawFilterParam(batch: SpriteBatch, x: Int, y: Int, filter: TerrarumAudioFilter, track: TerrarumAudioMixerTrack) {
         when (filter) {
             is Lowpass -> {
-                // https://www.desmos.com/calculator/dmhve2awxm
-                val f = filter.cutoff
-                val b = ln(24 / 24000.0) / -1.0
-                val a = 24.0
-                val perc = (ln(f / a) / b).toFloat()
+                val perc = linToLogPerc(filter.cutoff, 24.0, 24000.0).toFloat()
                 batch.color = COL_METER_GRAD2
                 Toolkit.fillArea(batch, x.toFloat(), y.toFloat(), stripW * perc, 14f)
                 batch.color = COL_METER_GRAD