feat: live operating-point fill + -6 dB refs on the gain curve

Add a per-channel input_level meter (post pre-gain, peak-with-decay) and use it
to shade the gain curve: a translucent fill under the curve from the floor up to
the current input, its right edge riding the curve (width = input, height =
output), plus a dot at the operating point. Add -6 dBFS reference lines on both
axes with a tick label.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -100,11 +100,13 @@ a first-class mode, not an afterthought.
 ### Per-Channel Compressor (× 4: low, mid, high, **all** — one `#[nested]` params struct reused)
 - `pre_gain_db` — drive into the compressor (−24…+36 dB, smoothed)
 - `detection` — peak / RMS level detection
+- `low_slope` — low-level shaper slope at the silence floor (1 = unity, >1 fans up/boost, <1 fans down/cut). **Serial**: reshapes the level *before* the threshold, so a boost can lift quiet material up into compression
+- `low_curve` — bends the low shaper toward a bounded saturation (0% = straight line) so the serial composition doesn't run away
 - `threshold_db`
 - `ratio` — 1.0 (off) to ∞ (limiting)
+- `knee_db` — soft knee width
 - `attack_ms`
 - `release_ms`
-- `knee_db` — soft knee width
 - `makeup_db` — makeup gain (−24…+24 dB)
 - `mix` — per-channel dry/wet mix (parallel compression); 0% = dry (a clean bypass), 100% = fully processed. Bands at 0% → simple full-band comp via the 'all' channel
 

src/dsp/compressor.rs

@@ -26,6 +26,16 @@ const MAX_CHANNELS: usize = 2;
 /// ~ -240 dBFS; keeps `log10` away from zero without affecting audible levels.
 const LEVEL_EPS: f32 = 1e-12;
 
+/// Silence-floor anchor for the below-threshold shaping: at/below this level the gain change is 0
+/// (silence stays silence), and the low region fans up/down from here toward the threshold. Matches
+/// the editor gain-curve's display floor.
+const LOW_ANCHOR_DB: f32 = -60.0;
+
+/// Max bulge (dB) the low-shaper curvature adds at the MIDDLE of the low region, at `|low_curve|`=1.
+/// Bipolar: positive bulges up (boost the quiet middle), negative bulges down (suppress). Zero at
+/// both ends (silence floor and the knee), so it never moves those anchors.
+const LOW_BULGE_MAX_DB: f32 = 12.0;
+
 /// Hardcoded RMS averaging window (one-pole time constant). Deliberately small; can be
 /// promoted to a parameter later.
 const RMS_WINDOW_MS: f32 = 5.0;
@@ -40,6 +50,11 @@ pub struct CompressorSettings {
     pub threshold_db: f32,
     pub ratio: f32,
     pub knee_db: f32,
+    /// Low shaper slope at the silence floor (1 = unity; >1 fans up/boost, <1 fans down/cut).
+    /// Reshapes the level the compressor sees (serial), anchored at the floor.
+    pub low_slope: f32,
+    /// Low shaper curvature, 0..1 (0 = straight line, 1 = max bend toward bounded saturation).
+    pub low_curve: f32,
     /// One-pole coefficient for the attack ramp (see [`Compressor::time_to_coef`]).
     pub attack_coef: f32,
     /// One-pole coefficient for the release ramp.
@@ -69,7 +84,8 @@ pub struct Compressor {
     mean_sq: f32,
     rms_coef: f32,
 
-    /// Smooth decoupled peak-detector state, expressed as dB of **attenuation** (>= 0).
+    /// Smooth decoupled peak-detector state, in dB of attenuation (signed: usually >= 0, but can go
+    /// negative = boost when `low_slope < 1`). The `max()` recurrence makes cut fast / boost slow.
     y1: f32, // release branch (peak-with-decay)
     yl: f32, // attack-smoothed output
 }
@@ -131,25 +147,56 @@ impl Compressor {
         }
     }
 
-    /// Static compressor curve. Returns gain reduction in dB (<= 0) for an input `level_db`.
-    /// Quadratic soft knee of width `knee_db`, centred on `threshold_db`. Also used by the editor's
-    /// gain-curve display, so it stays the single source of truth for the transfer shape.
-    pub fn gain_computer(level_db: f32, threshold_db: f32, ratio: f32, knee_db: f32) -> f32 {
+    /// Pure compressor transfer (threshold / ratio / quadratic soft knee). Returns gain reduction
+    /// in dB (<= 0) for an input `level_db`.
+    fn comp_gain_db(level_db: f32, threshold_db: f32, ratio: f32, knee_db: f32) -> f32 {
         let slope = 1.0 / ratio - 1.0; // <= 0 for ratio >= 1
         let over = level_db - threshold_db;
-
         if knee_db > 0.0 && 2.0 * over.abs() <= knee_db {
-            // Inside the knee: a parabola joining the two regions with a continuous slope.
             let x = over + knee_db * 0.5; // 0..knee
             slope * x * x / (2.0 * knee_db)
         } else if over > 0.0 {
-            // Above the knee (also covers the hard-knee case): linear region.
             slope * over
         } else {
             0.0
         }
     }
 
+    /// Low-level shaper gain in dB. Anchored at BOTH the silence floor ([`LOW_ANCHOR_DB`]) and the
+    /// knee (threshold). `low_slope` tilts the straight line between those anchors (1 = unity);
+    /// `low_curve` (-1..1) bulges that line in the middle without moving either endpoint — positive
+    /// bulges up (boost the quiet middle), negative down (suppress). Reshapes the level the
+    /// compressor then sees.
+    fn low_gain_db(level_db: f32, threshold_db: f32, low_slope: f32, low_curve: f32) -> f32 {
+        let d = level_db - LOW_ANCHOR_DB;
+        if d <= 0.0 {
+            return 0.0;
+        }
+        let span = (threshold_db - LOW_ANCHOR_DB).max(1.0); // floor -> threshold width
+        let t = (d / span).min(1.0); // normalized position, clamped at the knee
+        // Straight line anchored at the floor (t=0 -> 0) and the knee (t=1 -> (slope-1)*span).
+        let slope_line = (low_slope - 1.0) * span * t;
+        // Bipolar bulge: 0 at both ends, peaks (4·t·(1-t) = 1) at the middle.
+        let bulge = low_curve * LOW_BULGE_MAX_DB * 4.0 * t * (1.0 - t);
+        slope_line + bulge
+    }
+
+    /// Full static curve, **serial**: the low shaper reshapes the level, then the compressor's
+    /// threshold sees the shaped level. Returns total gain in dB (signed: negative = cut, positive
+    /// = boost). `gain = low + comp(level + low)`. Shared with the editor's gain-curve display —
+    /// single source of truth.
+    pub fn gain_computer(
+        level_db: f32,
+        threshold_db: f32,
+        ratio: f32,
+        knee_db: f32,
+        low_slope: f32,
+        low_curve: f32,
+    ) -> f32 {
+        let low = Self::low_gain_db(level_db, threshold_db, low_slope, low_curve);
+        low + Self::comp_gain_db(level_db + low, threshold_db, ratio, knee_db)
+    }
+
     /// The plugin's fixed reported latency in samples (the constant audio delay).
     pub fn latency(&self) -> u32 {
         self.fixed_delay as u32
@@ -199,7 +246,14 @@ impl Compressor {
         let detector = if set.use_rms { self.mean_sq.sqrt() } else { peak };
         let level_db = 20.0 * (detector + LEVEL_EPS).log10();
         // Desired attenuation in dB, as a positive quantity.
-        let target = -Self::gain_computer(level_db, set.threshold_db, set.ratio, set.knee_db);
+        let target = -Self::gain_computer(
+            level_db,
+            set.threshold_db,
+            set.ratio,
+            set.knee_db,
+            set.low_slope,
+            set.low_curve,
+        );
 
         // Smooth, decoupled peak detector (Giannoulis eq. 17–18) on the attenuation:
         //   y1 = max(target, release-smoothed y1)   (fast up / slow down "peak hold")
@@ -243,19 +297,40 @@ mod tests {
             lookahead_samples: 0,
             use_rms: false,
             mix: 1.0,
+            low_slope: 1.0,
+            low_curve: 0.0,
         }
     }
 
     #[test]
     fn below_threshold_is_untouched() {
         // -30 dB input, -20 dB threshold -> no reduction.
-        assert_eq!(Compressor::gain_computer(-30.0, -20.0, 4.0, 6.0), 0.0);
+        assert_eq!(Compressor::gain_computer(-30.0, -20.0, 4.0, 6.0, 1.0, 0.0), 0.0);
+    }
+
+    #[test]
+    fn low_shaper_serial_slope_and_bipolar_bulge() {
+        let thr = -18.0;
+        // Serial slope-only (no curve): boost lifts -30 by 30 dB to 0 dB -> 18 dB over threshold,
+        // comp pulls back (1/4 - 1)*18 = -13.5 -> net 16.5.
+        assert_close(Compressor::gain_computer(-30.0, thr, 4.0, 0.0, 2.0, 0.0), 16.5, 1e-3);
+        // Cut (slope 0.5) -> -15 dB; shaped to -45, still below threshold -> net -15.
+        assert_close(Compressor::gain_computer(-30.0, thr, 4.0, 0.0, 0.5, 0.0), -15.0, 1e-3);
+
+        // Curvature is a BIPOLAR bulge at the middle of the low region (unity slope here).
+        let mid = -39.0; // middle of [-60, -18]
+        let flat = Compressor::gain_computer(mid, thr, 4.0, 0.0, 1.0, 0.0);
+        let up = Compressor::gain_computer(mid, thr, 4.0, 0.0, 1.0, 1.0);
+        let down = Compressor::gain_computer(mid, thr, 4.0, 0.0, 1.0, -1.0);
+        assert!(up > flat && flat > down, "bipolar bulge expected: {down} < {flat} < {up}");
+        // Endpoints are unaffected by curvature (silence anchored).
+        assert_close(Compressor::gain_computer(-60.0, thr, 4.0, 0.0, 1.0, 1.0), 0.0, 1e-6);
     }
 
     #[test]
     fn above_knee_follows_ratio() {
         // 10 dB over threshold at 4:1 -> output only 2.5 dB over -> 7.5 dB reduction.
-        let r = Compressor::gain_computer(-10.0, -20.0, 4.0, 0.0);
+        let r = Compressor::gain_computer(-10.0, -20.0, 4.0, 0.0, 1.0, 0.0);
         assert_close(r, -7.5, 1e-4);
     }
 
@@ -264,11 +339,11 @@ mod tests {
         // At the upper knee edge the soft-knee and linear formulas must agree.
         let (t, ratio, knee) = (0.0, 4.0, 6.0);
         let edge = t + knee / 2.0;
-        let knee_val = Compressor::gain_computer(edge, t, ratio, knee);
+        let knee_val = Compressor::gain_computer(edge, t, ratio, knee, 1.0, 0.0);
         let linear_val = (1.0 / ratio - 1.0) * (edge - t);
         assert_close(knee_val, linear_val, 1e-4);
         // At the lower edge there is still no reduction.
-        assert_close(Compressor::gain_computer(t - knee / 2.0, t, ratio, knee), 0.0, 1e-6);
+        assert_close(Compressor::gain_computer(t - knee / 2.0, t, ratio, knee, 1.0, 0.0), 0.0, 1e-6);
     }
 
     #[test]

src/editor/gain_curve.rs

@@ -1,11 +1,14 @@
-//! Static gain-curve display (visualisation only): output level vs input level for the channel
-//! currently selected in the plot. Plots the full channel transfer for the wet path:
-//! `out = (in + pre_gain) + gain_reduction(in + pre_gain) + makeup`. Mix is not folded in (the
-//! curve shows the wet/100% path, matching the GR-meter convention); output is clamped at 0 dBFS.
+//! Static gain-curve display: output level vs input level for the channel currently selected in
+//! the plot. Plots the wet transfer `out = (in + pre_gain) + gain_reduction(...) + makeup` (mix not
+//! folded in; output clamped at 0 dBFS), plus a live **operating-point fill** under the curve up to
+//! the channel's current input level — its right edge rides the curve (width = input, height = out).
 
+use nih_plug::prelude::util;
 use nih_plug_egui::egui::{self, pos2, vec2, Align2, Color32, CornerRadius, FontId, Sense, Stroke};
+use std::sync::atomic::Ordering;
 
 use crate::dsp::compressor::Compressor;
+use crate::meters::Meters;
 use crate::params::Codename206Params;
 
 /// Side length of the square plot.
@@ -13,7 +16,7 @@ const CURVE_SIZE: f32 = 150.0;
 /// dB extent of both axes (bottom/left = FLOOR_DB, top/right = 0 dBFS).
 const FLOOR_DB: f32 = -60.0;
 
-pub(super) fn draw(ui: &mut egui::Ui, params: &Codename206Params, selected: usize) {
+pub(super) fn draw(ui: &mut egui::Ui, params: &Codename206Params, selected: usize, meters: &Meters) {
     let labels = ["LOW", "MID", "HIGH", "ALL"];
     let ch = selected.min(3);
     let cp = match ch {
@@ -26,6 +29,8 @@ pub(super) fn draw(ui: &mut egui::Ui, params: &Codename206Params, selected: usiz
     let threshold = cp.threshold_db.value();
     let ratio = cp.ratio.value();
     let knee = cp.knee_db.value();
+    let low_slope = cp.low_slope.value();
+    let low_curve = cp.low_curve.value();
     let makeup = cp.makeup_db.value();
 
     ui.label(format!("Curve: {}", labels[ch]));
@@ -41,6 +46,13 @@ pub(super) fn draw(ui: &mut egui::Ui, params: &Codename206Params, selected: usiz
     let x_for = |db: f32| left + (db - FLOOR_DB) / -FLOOR_DB * w;
     let y_for = |db: f32| bottom - (db - FLOOR_DB) / -FLOOR_DB * h;
 
+    // -6 dBFS reference lines on both axes.
+    let g6 = Color32::from_gray(38);
+    let x6 = x_for(-6.0);
+    let y6 = y_for(-6.0);
+    p.line_segment([pos2(x6, top), pos2(x6, bottom)], Stroke::new(1.0, g6));
+    p.line_segment([pos2(left, y6), pos2(right, y6)], Stroke::new(1.0, g6));
+
     // Unity reference (out = in), bottom-left to top-right.
     p.line_segment([pos2(left, bottom), pos2(right, top)], Stroke::new(1.0, Color32::from_gray(45)));
     // Threshold marker on the input axis — shifted left by pre-gain (the comp sees in + pre).
@@ -53,13 +65,42 @@ pub(super) fn draw(ui: &mut egui::Ui, params: &Codename206Params, selected: usiz
     for i in 0..=n {
         let in_db = FLOOR_DB + (i as f32 / n as f32) * -FLOOR_DB; // external input, -60..0
         let driven = in_db + pre;
-        let gr = Compressor::gain_computer(driven, threshold, ratio, knee); // <= 0 dB
+        let gr = Compressor::gain_computer(driven, threshold, ratio, knee, low_slope, low_curve); // signed dB
         let out_db = (driven + gr + makeup).clamp(FLOOR_DB, 0.0);
         pts.push(pos2(x_for(in_db), y_for(out_db)));
     }
+    // Operating-point fill: shade under the curve from the floor up to the current input level.
+    let driven_now = util::gain_to_db(meters.input_level[ch].load(Ordering::Relaxed));
+    let ext_in = (driven_now - pre).clamp(FLOOR_DB, 0.0); // external input -> curve x
+    let x_now = x_for(ext_in);
+    let fill_col = Color32::from_rgba_unmultiplied(120, 200, 160, 45);
+    for seg in pts.windows(2) {
+        let a = seg[0];
+        let mut b = seg[1];
+        if a.x >= x_now {
+            break;
+        }
+        if b.x > x_now {
+            let f = ((x_now - a.x) / (b.x - a.x)).clamp(0.0, 1.0); // clip the last quad at x_now
+            b = pos2(x_now, a.y + (b.y - a.y) * f);
+        }
+        p.add(egui::Shape::convex_polygon(
+            vec![pos2(a.x, bottom), a, b, pos2(b.x, bottom)],
+            fill_col,
+            Stroke::NONE,
+        ));
+    }
+
     p.add(egui::Shape::line(pts, Stroke::new(1.6, Color32::from_rgb(120, 200, 160))));
 
-    // Corner dB ticks.
+    // Operating-point dot, on the curve at the current input.
+    let driven = ext_in + pre;
+    let gr = Compressor::gain_computer(driven, threshold, ratio, knee, low_slope, low_curve);
+    let out_op = (driven + gr + makeup).clamp(FLOOR_DB, 0.0);
+    p.circle_filled(pos2(x_now, y_for(out_op)), 3.0, Color32::from_rgb(235, 240, 235));
+
+    // Corner dB ticks + the -6 dB reference.
     p.text(pos2(left + 1.0, top + 1.0), Align2::LEFT_TOP, "0", FontId::proportional(9.0), Color32::from_gray(90));
     p.text(pos2(left + 1.0, bottom - 1.0), Align2::LEFT_BOTTOM, "-60", FontId::proportional(9.0), Color32::from_gray(90));
+    p.text(pos2(x6 + 2.0, bottom - 1.0), Align2::LEFT_BOTTOM, "-6", FontId::proportional(9.0), Color32::from_gray(80));
 }

src/editor/mod.rs

@@ -47,10 +47,15 @@ pub(crate) fn create(params: Arc<Codename206Params>, meters: Arc<Meters>) -> Opt
 
             // One column of controls for a single compressor channel (placeholder layout).
             let band_col = |ui: &mut egui::Ui, title: &str, p: &CompressorParams| {
+                // Roughly in signal order: input drive -> low shaper -> compressor -> output.
                 ui.strong(title);
                 ui.label("Pre-gain");
                 ui.add(widgets::ParamSlider::for_param(&p.pre_gain_db, setter));
                 ui.add(widgets::ParamSlider::for_param(&p.detection, setter));
+                ui.label("Low Slope");
+                ui.add(widgets::ParamSlider::for_param(&p.low_slope, setter));
+                ui.label("Low Curve");
+                ui.add(widgets::ParamSlider::for_param(&p.low_curve, setter));
                 ui.label("Threshold");
                 ui.add(widgets::ParamSlider::for_param(&p.threshold_db, setter));
                 ui.label("Ratio");
@@ -79,7 +84,7 @@ pub(crate) fn create(params: Arc<Codename206Params>, meters: Arc<Meters>) -> Opt
                         // Gain curve (left, square) beside the scrolling plot (right, fills the rest).
                         let selected = state.plot.selected;
                         ui.horizontal_top(|ui| {
-                            ui.vertical(|ui| gain_curve::draw(ui, &params, selected));
+                            ui.vertical(|ui| gain_curve::draw(ui, &params, selected, &meters));
                             ui.vertical(|ui| plot::draw(ui, &meters, &mut state.plot));
                         });
                         ui.separator();

src/lib.rs

@@ -211,6 +211,7 @@ impl Plugin for Codename206 {
         let num_samples = buffer.samples();
         let mut lvl_l = [0.0f32; meters::NUM_CHANNELS];
         let mut lvl_r = [0.0f32; meters::NUM_CHANNELS];
+        let mut inp = [0.0f32; meters::NUM_CHANNELS]; // mono input level (detector / gain-curve x)
         let mut gr = [0.0f32; meters::NUM_CHANNELS];
         let mut lim_gr = 0.0f32;
 
@@ -245,6 +246,8 @@ impl Plugin for Codename206 {
                 }
                 band_set[b].makeup_db = band_params[b].makeup_db.smoothed.next();
                 band_set[b].mix = band_params[b].mix.smoothed.next();
+                band_set[b].low_slope = band_params[b].low_slope.smoothed.next();
+                band_set[b].low_curve = band_params[b].low_curve.smoothed.next();
                 self.comps[b].process(&band_in[b][..n], &mut band_out[b][..n], &band_set[b]);
                 for ch in 0..n {
                     summed[ch] += band_out[b][ch];
@@ -255,6 +258,7 @@ impl Plugin for Codename206 {
                     let out_r = band_out[b][r].abs();
                     // Wet gain reduction (what the comp computes), independent of the mix.
                     let g = self.comps[b].gain_reduction_db();
+                    inp[b] = inp[b].max(in_mono);
                     lvl_l[b] = lvl_l[b].max(out_l);
                     lvl_r[b] = lvl_r[b].max(out_r);
                     gr[b] = gr[b].max(g);
@@ -273,6 +277,8 @@ impl Plugin for Codename206 {
             }
             all_set.makeup_db = self.params.all.makeup_db.smoothed.next();
             all_set.mix = self.params.all.mix.smoothed.next();
+            all_set.low_slope = self.params.all.low_slope.smoothed.next();
+            all_set.low_curve = self.params.all.low_curve.smoothed.next();
             self.comps[ALL].process(&summed[..n], &mut out_frame[..n], &all_set);
 
             // Output brickwall limiter.
@@ -283,6 +289,7 @@ impl Plugin for Codename206 {
                 let out_l = out_frame[0].abs();
                 let out_r = out_frame[r].abs();
                 let g = self.comps[ALL].gain_reduction_db();
+                inp[ALL] = inp[ALL].max(in_mono);
                 lvl_l[ALL] = lvl_l[ALL].max(out_l);
                 lvl_r[ALL] = lvl_r[ALL].max(out_r);
                 gr[ALL] = gr[ALL].max(g);
@@ -323,6 +330,7 @@ impl Plugin for Codename206 {
             for i in 0..meters::NUM_CHANNELS {
                 meters::decay_store(&self.meters.level_l[i], lvl_l[i], w);
                 meters::decay_store(&self.meters.level_r[i], lvl_r[i], w);
+                meters::decay_store(&self.meters.input_level[i], inp[i], w);
                 meters::decay_store(&self.meters.gain_reduction_db[i], gr[i], w);
             }
             meters::decay_store(&self.meters.limiter_gr_db, lim_gr, w);

src/meters.rs

@@ -26,6 +26,9 @@ pub struct Meters {
     pub level_l: [AtomicF32; NUM_CHANNELS],
     /// Right output level per channel (== left for mono signals).
     pub level_r: [AtomicF32; NUM_CHANNELS],
+    /// Mono **input** level per channel (post pre-gain = what the compressor detects). Drives the
+    /// gain-curve operating-point fill. Peak-with-decay.
+    pub input_level: [AtomicF32; NUM_CHANNELS],
     /// Compressor gain reduction per channel in **dB (>= 0)**. Mono by design — detection is
     /// stereo-linked, so the same gain applies to both channels.
     pub gain_reduction_db: [AtomicF32; NUM_CHANNELS],
@@ -40,6 +43,7 @@ impl Default for Meters {
         Self {
             level_l: std::array::from_fn(|_| AtomicF32::new(0.0)),
             level_r: std::array::from_fn(|_| AtomicF32::new(0.0)),
+            input_level: std::array::from_fn(|_| AtomicF32::new(0.0)),
             gain_reduction_db: std::array::from_fn(|_| AtomicF32::new(0.0)),
             limiter_gr_db: AtomicF32::new(0.0),
             scope: ScopeRing::default(),
@@ -55,6 +59,7 @@ impl Meters {
         for i in 0..NUM_CHANNELS {
             self.level_l[i].store(0.0, Ordering::Relaxed);
             self.level_r[i].store(0.0, Ordering::Relaxed);
+            self.input_level[i].store(0.0, Ordering::Relaxed);
             self.gain_reduction_db[i].store(0.0, Ordering::Relaxed);
         }
         self.limiter_gr_db.store(0.0, Ordering::Relaxed);

src/params.rs

@@ -68,6 +68,13 @@ pub struct CompressorParams {
     pub ratio: FloatParam,
     #[id = "knee"]
     pub knee_db: FloatParam,
+    /// Low shaper slope at the silence floor (1 = unity; >1 fans up/boost, <1 fans down/cut).
+    #[id = "lowslope"]
+    pub low_slope: FloatParam,
+    /// Low shaper curvature (−1..1): bipolar mid-bulge, 0 = straight. +bulges up (boost quiet
+    /// middle), − bulges down (suppress). Endpoints (silence + knee) stay fixed.
+    #[id = "lowcurve"]
+    pub low_curve: FloatParam,
     #[id = "attack"]
     pub attack_ms: FloatParam,
     #[id = "release"]
@@ -168,6 +175,19 @@ impl Default for CompressorParams {
                 .with_unit(" dB")
                 .with_value_to_string(formatters::v2s_f32_rounded(1)),
 
+            low_slope: FloatParam::new(
+                "Low Slope",
+                1.0,
+                FloatRange::Skewed { min: 0.5, max: 3.0, factor: FloatRange::skew_factor(-1.0) },
+            )
+            .with_smoother(SmoothingStyle::Linear(20.0))
+            .with_value_to_string(formatters::v2s_f32_rounded(2)),
+
+            low_curve: FloatParam::new("Low Curve", 0.0, FloatRange::Linear { min: -1.0, max: 1.0 })
+                .with_smoother(SmoothingStyle::Linear(20.0))
+                .with_value_to_string(formatters::v2s_f32_percentage(0))
+                .with_string_to_value(formatters::s2v_f32_percentage()),
+
             attack_ms: FloatParam::new(
                 "Attack",
                 10.0,
@@ -207,6 +227,8 @@ pub fn build_settings(
         threshold_db: p.threshold_db.value(),
         ratio: p.ratio.value(),
         knee_db: p.knee_db.value(),
+        low_slope: p.low_slope.value(),
+        low_curve: p.low_curve.value(),
         attack_coef: Compressor::time_to_coef(p.attack_ms.value(), sample_rate),
         release_coef: Compressor::time_to_coef(p.release_ms.value(), sample_rate),
         makeup_db: 0.0,