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Fix filter env: restore unipolar modulation so all env knobs are responsive

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Reverts the sustain-relative modulation that made F.ENV SUS and the
cutoff knob feel dead while a note was held. The envelope now modulates
up from the base cutoff; at env amount 0 the cutoff equals the knob, and
lowering env amount darkens the held tone as expected.

Also extends the filter to 24/48 dB modes (extra TPT stages), adds the
matching combobox options, gives knobs a real blurred drop shadow, and
updates the AGENTS.md filterType choice count.
This commit is contained in:
Armin 2026-08-13 14:15:41 +02:00
commit a1cd68b6b3
5 changed files with 38 additions and 18 deletions
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2
AGENTS.md
View file

@ -101,7 +101,7 @@ Osc1 + Osc2 → Amplitude Envelope × Velocity → Filter (cutoff modulated by F
| osc2Fine | OSC2 Fine | -100..100 | 7 |
| osc2Level | OSC2 Level | 0..1 | 0.7 |
| phaseOffset | Phase Offset | 0..1 | 0.5 |
| filterType | Filter Type | Choice(5) | 0 (LP12)|
| filterType | Filter Type | Choice(9) | 0 (LP12)|
| filterCutoff | Filter Cutoff | 20..20000 (log) | 8000 |
| filterRes | Filter Res | 0..1 | 0.3 |
| filterEnvAmt | Filter Env Amt | 0..1 | 0 |

25
Source/DSP/Filter.h
View file

@ -2,7 +2,8 @@
#include <cmath>
#include <algorithm>
enum class FilterType { LowPass12 = 0, LowPass24, BandPass, HighPass, Notch, NumTypes };
enum class FilterType { LowPass12 = 0, LowPass24, BandPass, HighPass, Notch,
BandPass24, HighPass24, Notch24, LowPass48, NumTypes };
class Filter {
public:
@ -12,7 +13,7 @@ public:
}
void reset() {
for (int i = 0; i < 4; ++i)
for (int i = 0; i < 8; ++i)
stage[i] = 0.0f;
gCoeff = 0.0f;
gTarget = 0.0f;
@ -52,12 +53,30 @@ public:
stage[2] = g * hp2 + bp2;
stage[3] = g * bp2 + lp2;
// Stage 3 (fed by the stage-2 lowpass) — 36 dB
float hp3 = (lp2 - (k + g) * stage[4] - stage[5]) / denom;
float bp3 = g * hp3 + stage[4];
float lp3 = g * bp3 + stage[5];
stage[4] = g * hp3 + bp3;
stage[5] = g * bp3 + lp3;
// Stage 4 (fed by the stage-3 lowpass) — 48 dB
float hp4 = (lp3 - (k + g) * stage[6] - stage[7]) / denom;
float bp4 = g * hp4 + stage[6];
float lp4 = g * bp4 + stage[7];
stage[6] = g * hp4 + bp4;
stage[7] = g * bp4 + lp4;
switch (filterType) {
case FilterType::LowPass12: return lp;
case FilterType::LowPass24: return lp2;
case FilterType::BandPass: return bp;
case FilterType::HighPass: return hp;
case FilterType::Notch: return input - bp;
case FilterType::BandPass24: return bp2;
case FilterType::HighPass24: return hp2;
case FilterType::Notch24: return input - bp2;
case FilterType::LowPass48: return lp4;
case FilterType::NumTypes: return input;
}
return lp;
@ -66,7 +85,7 @@ public:
private:
static constexpr float pi = 3.14159265358979323846f;
double sampleRate = 44100.0;
float stage[4] = {0.0f, 0.0f, 0.0f, 0.0f};
float stage[8] = {0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f};
float gCoeff = 0.0f, gTarget = 0.0f;
float kCoeff = 2.0f, kTarget = 2.0f;

15
Source/DSP/Voice.h
View file

@ -129,13 +129,12 @@ public:
right *= noteVelocity * envSample;
// Filter cutoff with env + keytrack.
// Modulate RELATIVE to the envelope's sustain level so the held
// (sustain) cutoff always equals the base cutoff knob regardless of
// env amount — the envelope only opens above (attack) and closes
// below (release) that centre. This keeps the cutoff knob audible
// at any env amount instead of collapsing when env amt is lowered.
float modCutoff = filterCutoff * std::pow(2.0f,
(fEnvSample - filterEnvSustain) * filterEnvAmount * 4.0f);
// Unipolar modulation UP from the base cutoff: the envelope (0..1)
// multiplied by env amount adds brightness on top of the cutoff
// knob, never going below it. Every env knob (attack/decay/
// sustain/release) shapes the response, and at env amount 0 the
// cutoff equals the knob.
float modCutoff = filterCutoff * std::pow(2.0f, fEnvSample * filterEnvAmount * 4.0f);
float keyTrackFactor = std::pow(2.0f, (static_cast<float>(currentMidiNote) - 60.0f) / 12.0f * keyTrack);
modCutoff *= keyTrackFactor;
@ -197,7 +196,6 @@ public:
filterResonance = res;
filterType = ft;
filterEnvAmount = fEnvAmt;
filterEnvSustain = fSus;
keyTrack = kTrack;
pan = p;
drive = std::max(drv, 1.001f);
@ -252,7 +250,6 @@ private:
float filterResonance = 0.7f;
FilterType filterType = FilterType::LowPass12;
float filterEnvAmount = 0.0f;
float filterEnvSustain = 0.5f;
float keyTrack = 0.5f;
float pan = 0.0f;
float drive = 1.5f;

11
Source/PluginEditor.cpp
View file

@ -47,9 +47,11 @@ void KnobLookAndFeel::drawRotarySlider(juce::Graphics& g, int x, int y, int widt
auto rw = radius * 2.0f;
auto angle = rotaryStartAngle + sliderPos * (rotaryEndAngle - rotaryStartAngle);
// Drop shadow
g.setColour(juce::Colour(0x40000000));
g.fillEllipse(rx + 2.0f, ry + 3.0f, rw, rw);
// Blurred drop shadow
juce::DropShadow knobShadow(juce::Colour(0x55000000), 10, juce::Point<int>(0, 5));
juce::Path shadowPath;
shadowPath.addEllipse(juce::Rectangle<float>(rx, ry, rw, rw));
knobShadow.drawForPath(g, shadowPath);
// Outer bevel (dark bottom-right, light top-left)
auto bevelPath = juce::Path();
@ -620,7 +622,8 @@ MainContentComponent::MainContentComponent(ChromaFlockProcessor& p)
setupParam(phaseOffsetKnob, phaseOffsetAttach, "phaseOffset", "PHASE");
setupLabel(filterLabel, "FILTER");
setupCB(filterTypeBox, filterTypeAttach, "filterType", {"LP 12dB", "LP 24dB", "Band Pass", "High Pass", "Notch"});
setupCB(filterTypeBox, filterTypeAttach, "filterType", {"LP 12dB", "LP 24dB", "Band Pass", "High Pass", "Notch",
"Band Pass 24", "High Pass 24", "Notch 24", "LP 48dB"});
setupParam(filterCutoffKnob, filterCutoffAttach, "filterCutoff", "CUTOFF");
setupParam(filterResKnob, filterResAttach, "filterRes", "RES");
setupParam(filterEnvAmtKnob, filterEnvAmtAttach, "filterEnvAmt", "ENV AMT");

3
Source/PluginProcessor.cpp
View file

@ -91,7 +91,8 @@ juce::AudioProcessorValueTreeState::ParameterLayout ChromaFlockProcessor::create
// FILTER
layout.add(std::make_unique<juce::AudioParameterChoice>(
juce::ParameterID{"filterType", 1}, "Filter Type",
juce::StringArray{"LP 12dB", "LP 24dB", "Band Pass", "High Pass", "Notch"}, 0));
juce::StringArray{"LP 12dB", "LP 24dB", "Band Pass", "High Pass", "Notch",
"Band Pass 24", "High Pass 24", "Notch 24", "LP 48dB"}, 0));
layout.add(std::make_unique<juce::AudioParameterFloat>(
juce::ParameterID{"filterCutoff", 1}, "Filter Cutoff",
juce::NormalisableRange<float>(