From 70aca67dbdf180aca3f8c24517f4f34dec01e637 Mon Sep 17 00:00:00 2001
From: Paul <baconpaul@users.noreply.github.com>
Date: Sun, 13 Nov 2022 11:21:12 -0500
Subject: [PATCH] Add an optional LFO onepole for FROM_LAST envelope mode
 (#6699)

* Add an optional LFO onepole for FROM_LAST envelope mode

In envelope mode with high deform in FROM_LAST mode the
signal from the envelope is not continuous. This is basically
unsolvable analytically - the deform plus state is too hard -
and so leave it on by default but add an optional one pole to
smooth it out, which may be useful in some cases.

Expose configurations of that to the rack LFO

Addresses https://github.com/surge-synthesizer/surge-rack/issues/607
---
 src/common/dsp/modulators/LFOModulationSource.cpp | 13 +++++++++++++
 src/common/dsp/modulators/LFOModulationSource.h   |  4 ++++
 2 files changed, 17 insertions(+)

diff --git a/src/common/dsp/modulators/LFOModulationSource.cpp b/src/common/dsp/modulators/LFOModulationSource.cpp
index b6437342070..5ed50e76450 100644
--- a/src/common/dsp/modulators/LFOModulationSource.cpp
+++ b/src/common/dsp/modulators/LFOModulationSource.cpp
@@ -77,6 +77,9 @@ void LFOModulationSource::assign(SurgeStorage *storage, LFOStorage *lfo, pdata *
     {
         wf_history[i] = 0.f;
     }
+
+    for (int i = 0; i < 3; ++i)
+        onepoleState[i] = 0.f;
 }
 
 float LFOModulationSource::bend1(float x)
@@ -1289,6 +1292,16 @@ void LFOModulationSource::process_block()
             output_multi[1] *= useenvval;
             output_multi[1] += useenv0;
         }
+
+        if (envRetrigMode == FROM_LAST && lfo->deform.deform_type != type_3)
+        {
+            // Now appy the one pole
+            float alpha = onepoleFactor;
+            output_multi[0] = (1.0 - alpha) * output_multi[0] + alpha * onepoleState[0];
+            output_multi[1] = (1.0 - alpha) * output_multi[1] + alpha * onepoleState[1];
+            onepoleState[0] = output_multi[0];
+            onepoleState[1] = output_multi[1];
+        }
     }
 }
 
diff --git a/src/common/dsp/modulators/LFOModulationSource.h b/src/common/dsp/modulators/LFOModulationSource.h
index 92a751e3448..752a0074ce0 100644
--- a/src/common/dsp/modulators/LFOModulationSource.h
+++ b/src/common/dsp/modulators/LFOModulationSource.h
@@ -111,6 +111,8 @@ class LFOModulationSource : public ModulationSource
     inline int getEnvState() { return env_state; }
     inline int getStep() { return step; }
 
+    float onepoleFactor{0};
+
   private:
     pdata *localcopy;
     bool phaseInitialized;
@@ -128,6 +130,8 @@ class LFOModulationSource : public ModulationSource
     int step, shuffle_id;
     int magn, rate, iattack, idecay, idelay, ihold, isustain, irelease, startphase, ideform;
 
+    float onepoleState[3];
+
     std::default_random_engine gen;
     std::uniform_real_distribution<float> distro;
     std::function<float()> urng;