commit da4a5e14d5894bf3fdfbe7be3657d42cf63c78b9
parent 9c844e34e80be4a45ced763a5eff3ea42f44b417
Author: minerva-jupiter <ryouturn@gmail.com>
Date: Tue, 17 Mar 2026 20:15:40 +0900
feat(synth): Add resonant filter and amplitude envelope
Diffstat:
| M | src/lib.rs | | | 143 | ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- |
1 file changed, 138 insertions(+), 5 deletions(-)
diff --git a/src/lib.rs b/src/lib.rs
@@ -12,6 +12,8 @@ struct Mooxide {
midi_note_id: u8,
midi_note_frequency: f32,
midi_note_velocity: Smoother<f32>,
+ filter_biquad: [f32; 4],
+ note_time: u32,
}
#[derive(Enum, PartialEq, Clone, Copy)]
@@ -91,6 +93,25 @@ struct MooxideParams {
#[id = "noise_mix"]
pub noise_mix: FloatParam,
+ #[id = "filter_cutoff"]
+ pub filter_cutoff: FloatParam,
+ #[id = "filter_emphasis"]
+ pub filter_emphasis: FloatParam,
+ #[id = "filter_contour"]
+ pub filter_contour: FloatParam,
+ #[id = "filter_attack"]
+ pub filter_attack: FloatParam,
+ #[id = "filter_decay"]
+ pub filter_decay: FloatParam,
+ #[id = "filter_sustain"]
+ pub filter_sustain: FloatParam,
+ #[id = "contour_attack"]
+ pub contour_attack: FloatParam,
+ #[id = "contour_decay"]
+ pub contour_decay: FloatParam,
+ #[id = "contour_sustain"]
+ pub contour_sustain: FloatParam,
+
#[id = "gain"]
pub gain: FloatParam,
}
@@ -104,6 +125,8 @@ impl Default for Mooxide {
midi_note_id: 0,
midi_note_frequency: 1.0,
midi_note_velocity: Smoother::new(SmoothingStyle::Linear(5.0)),
+ filter_biquad: [0.0; 4],
+ note_time: 0,
}
}
}
@@ -148,6 +171,71 @@ impl Default for MooxideParams {
noise: EnumParam::new("Noise", NoiseKind::White),
noise_mix: FloatParam::new("Mix", 1.0, FloatRange::Linear { min: 0.0, max: 1.0 }),
+
+ filter_cutoff: FloatParam::new(
+ "Filter Cutoff Frequency",
+ 0.0,
+ FloatRange::Linear {
+ min: -5.0,
+ max: 5.0,
+ },
+ ),
+ filter_emphasis: FloatParam::new(
+ "Filter Emphasis",
+ 0.5,
+ FloatRange::Linear { min: 0.0, max: 1.0 },
+ ),
+ filter_contour: FloatParam::new(
+ "Filter Contour",
+ 0.5,
+ FloatRange::Linear { min: 0.0, max: 1.0 },
+ ),
+ filter_attack: FloatParam::new(
+ "Filter Attack Time",
+ 0.6,
+ FloatRange::Skewed {
+ min: 0.001,
+ max: 20.0,
+ factor: FloatRange::skew_factor(-0.9),
+ },
+ ),
+ filter_decay: FloatParam::new(
+ "Filter Decay Time",
+ 0.6,
+ FloatRange::Skewed {
+ min: 0.001,
+ max: 20.0,
+ factor: FloatRange::skew_factor(-0.9),
+ },
+ ),
+ filter_sustain: FloatParam::new(
+ "Filter Sustain Level",
+ 0.5,
+ FloatRange::Linear { min: 0.0, max: 1.0 },
+ ),
+ contour_attack: FloatParam::new(
+ "Contour Attack Time",
+ 0.6,
+ FloatRange::Skewed {
+ min: 0.001,
+ max: 20.0,
+ factor: FloatRange::skew_factor(-0.9),
+ },
+ ),
+ contour_decay: FloatParam::new(
+ "Contour Decay Time",
+ 0.6,
+ FloatRange::Skewed {
+ min: 0.001,
+ max: 20.0,
+ factor: FloatRange::skew_factor(-0.9),
+ },
+ ),
+ contour_sustain: FloatParam::new(
+ "Contour Sustain Level",
+ 0.5,
+ FloatRange::Linear { min: 0.0, max: 1.0 },
+ ),
}
}
}
@@ -204,6 +292,46 @@ impl Mooxide {
}
}
}
+
+ fn envelope(&self) -> f32 {
+ let time = self.note_time as f32 / self.sample_rate;
+ let attack_phase = (time / self.params.contour_attack.value()).clamp(0.0, 1.0);
+ let decay_phase = ((time - self.params.contour_attack.value())
+ / self.params.contour_decay.value())
+ .clamp(0.0, 1.0);
+ attack_phase * (1.0 - decay_phase) + (self.params.contour_sustain.value() * decay_phase)
+ }
+
+ fn filter_envelope(&self) -> f32 {
+ let time = self.note_time as f32 / self.sample_rate;
+ let attack_phase = (time / self.params.filter_attack.value()).clamp(0.0, 1.0);
+ let decay_phase = ((time - self.params.filter_attack.value())
+ / self.params.filter_decay.value())
+ .clamp(0.0, 1.0);
+ attack_phase * (1.0 - decay_phase) + (self.params.filter_sustain.value() * decay_phase)
+ }
+
+ fn filter(&mut self, input: f32) -> f32 {
+ // https://www.utsbox.com/?page_id=523
+ let openture = self.midi_note_frequency
+ * (2.0 + self.filter_envelope() + (self.params.filter_cutoff.value() / 5.0));
+ let omega = 2.0 * std::f32::consts::PI * openture / self.sample_rate;
+ let alpha = omega.sin() / 2.0 / self.params.filter_emphasis.value();
+ let a0 = 1.0 + alpha;
+ let a1 = -2.0 * omega.cos();
+ let a2 = 1.0 - alpha;
+ let b0 = (1.0 - omega.cos()) / 2.0;
+ let b1 = 1.0 - omega.cos();
+ let b2 = (1.0 - omega.cos()) / 2.0;
+ let y = b0 / a0 * input + b1 / a0 * self.filter_biquad[0] + b2 / a0 * self.filter_biquad[1]
+ - a1 / a0 * self.filter_biquad[2]
+ - a2 / a0 * self.filter_biquad[3];
+ self.filter_biquad[1] = self.filter_biquad[0];
+ self.filter_biquad[0] = input;
+ self.filter_biquad[3] = self.filter_biquad[2];
+ self.filter_biquad[2] = y;
+ y
+ }
}
impl Plugin for Mooxide {
@@ -293,6 +421,8 @@ impl Plugin for Mooxide {
self.midi_note_frequency = util::midi_note_to_freq(note);
self.midi_note_velocity
.set_target(self.sample_rate, velocity);
+ self.filter_biquad = [0.0; 4];
+ self.note_time = 0;
}
NoteEvent::NoteOff { note, .. } if note == self.midi_note_id => {
self.midi_note_velocity.set_target(self.sample_rate, 0.0);
@@ -330,15 +460,18 @@ impl Plugin for Mooxide {
let noise = self.noise(self.params.noise.value());
- (osc1 * self.params.osc1_mix.value()
- + osc2 * self.params.osc2_mix.value()
- + osc3 * self.params.osc3_mix.value()
- + noise * self.params.noise_mix.value())
- * self.midi_note_velocity.next()
+ self.filter(
+ (osc1 * self.params.osc1_mix.value()
+ + osc2 * self.params.osc2_mix.value()
+ + osc3 * self.params.osc3_mix.value()
+ + noise * self.params.noise_mix.value())
+ * self.midi_note_velocity.next(),
+ ) * self.envelope()
};
for sample in channel_samples {
*sample = displacement * util::db_to_gain_fast(gain);
}
+ self.note_time += 1;
}
ProcessStatus::KeepAlive
