From bbaff2f4c5d379276034976503ce026dbd153132 Mon Sep 17 00:00:00 2001
From: Grant Shangreaux <grant@unabridgedsoftware.com>
Date: Sun, 7 Nov 2021 20:44:12 -0600
Subject: Fix: frequency modulation implementation to be correct :|

---
 klangfarb/main.gd      | 9 +++++----
 klangfarbrs/src/lib.rs | 4 ++--
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/klangfarb/main.gd b/klangfarb/main.gd
index 4397a7e..9f4ffae 100644
--- a/klangfarb/main.gd
+++ b/klangfarb/main.gd
@@ -20,8 +20,8 @@ export(float, 20, 8000, 5) var cutoff = 6000
 
 # Frequency Modulation
 export(bool) var frequency_modulation = false
-export(float, 0.0, 100.0, 0.1) var fm_frequency = 1.0
-export(float, 0.0, 10.0, 0.1) var fm_amplitude = 0.1
+export(float, 0.0, 50.0, 0.1) var fm_multiplier = 1.0
+export(float, 0.0, 1000.0, 1.0) var fm_index = 1.0
 
 # load the GDNative script connected to the rust lib
 var MonoSynth = preload("res://MonoSynth.gdns")
@@ -57,8 +57,8 @@ func _process(_delta):
 		synth.frequency(freq) 
 		synth.phasor_bend(phasor_bend)
 		synth.frequency_modulation(frequency_modulation)
-		synth.fm_frequency(fm_frequency)
-		synth.fm_depth(fm_amplitude)
+		synth.fm_frequency(fm_multiplier * freq)
+		synth.fm_depth(fm_index)
 		_check_waveform()
 		_fill_buffer()
 
@@ -81,3 +81,4 @@ func _input(event):
 		freq = event.position.x
 #		phasor_bend.x = event.position.x / 1024
 #		phasor_bend.y = event.position.y / 600
+		fm_multiplier = 600 / (event.position.y + 1)
diff --git a/klangfarbrs/src/lib.rs b/klangfarbrs/src/lib.rs
index 07e9cc7..fafb5c0 100644
--- a/klangfarbrs/src/lib.rs
+++ b/klangfarbrs/src/lib.rs
@@ -157,7 +157,7 @@ impl MonoSynth {
             release: 0,
             cutoff: 0.0,
             frequency_modulation: false,
-            fm_frequency: 30000.0,
+            fm_frequency: 10.0,
             fm_depth: 0.1,
             fm_phasor: Phasor { phase: 0.0 }
         }
@@ -234,7 +234,7 @@ impl MonoSynth {
             if self.frequency_modulation {
                 let modulation_value = Osc::generate_sample(&Waveform::Sine, self.fm_phasor.phase) * self.fm_depth;
                 self.fm_phasor.phase = self.fm_phasor.next_phase(self.fm_frequency, self.sample_rate);
-                next_phase = self.phasor.next_phase(self.frequency * modulation_value, self.sample_rate);
+                next_phase = self.phasor.next_phase(self.frequency + modulation_value, self.sample_rate);
             } else {
                 next_phase = self.phasor.next_phase(self.frequency, self.sample_rate);
             }
-- 
cgit v1.2.3