Terion

Real-time stereo analyzer and mid-side vector scope audio plugin for macOS.

Terion visualizes the stereo field of any audio signal using a mid/side coordinate system. The X axis represents the Side (difference) signal and the Y axis represents the Mid (sum) signal, plotted as an XY vectorscope with a configurable phosphor-style fading trail. It is an analysis-only plugin - audio passes through unmodified.

Features

Mid/Side vectorscope - XY plot with phase-mapped color (correlated content in cyan/blue, out-of-phase content shifting toward red)
Phosphor trail - configurable fade time from 0.1 to 10 seconds for persistent visual history
Real-time stereo metrics - correlation, stereo width, mid/side levels, balance, phase angle, crest factor, and peak/RMS levels
Freeze - capture and hold the current display for inspection
Resizable UI - scales from 630×420 up to 1890×1890, with preset scale factors (100/125/150/200/250/300%)
Custom arc knobs - clean rotary controls with teal arc indicators
VST3 and Audio Unit formats

Requirements

macOS
CMake 3.22 or later
C++17 compiler (Xcode command line tools)
JUCE framework (cloned automatically by make juce, or use an existing ~/JUCE install)

Building

make all        # configure + build (Release)
make install    # build, codesign, un-quarantine, install to ~/Library/Audio/Plug-Ins

Makefile targets

Target	Description
`make all`	Configure and build
`make juce`	Clone JUCE into `third_party/JUCE` (skipped if `~/JUCE` exists)
`make configure`	Run CMake configure only
`make build`	Compile only
`make install`	Build, codesign (ad-hoc), strip quarantine, install to user plug-in dirs
`make sign`	Codesign installed bundles
`make unquarantine`	Strip Gatekeeper quarantine xattrs from installed bundles
`make uninstall`	Remove installed VST3 and AU bundles
`make clean`	Remove `build/`
`make deepclean`	Remove `build/`, `third_party/`, and stray artefacts

Variables

Variable	Default	Description
`BUILD_DIR`	`build`	CMake build directory
`CONFIG`	`Release`	Build configuration
`JOBS`	`$(ncpu)`	Parallel compilation jobs
`CODESIGN_ID`	(empty = ad-hoc)	Codesign identity string
`JUCE_DIR`	auto-detected	Override JUCE source location

Parameters

Parameter	Range	Description
Fade	0.1 – 10 s	Trail persistence time
Sensitivity	-12 – +24 dB	Input gain for M/S decode
Dot size	0.5 – 8.0 px	Size of each plotted point
Smoothing	0 – 0.99	One-pole smoothing on M/S signals
Afterglow	0 – 5 s	Extra lingers of the trail after the fade time
Freeze	on/off	Stop capturing new points

Project structure

terion/
├── CMakeLists.txt          # JUCE plugin build configuration
├── Makefile                # Build/install/sign wrapper
├── Source/
│   ├── PluginProcessor.*   # Audio engine: M/S decode, ring buffer, metrics
│   ├── PluginEditor.*      # UI layout, knobs, freeze, scale, footer
│   ├── VectorScope.*       # XY scope rendering, trail, legends, overlay
│   ├── ArcKnob.*           # Custom rotary arc slider
│   └── Version.h.in        # Git hash/timestamp template
└── third_party/JUCE/       # JUCE framework (auto-cloned, gitignored)

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