Ambi Encoder Wave Terrain

s3g Ambi Encoder Wave Terrain is a 64-voice wave-terrain instrument with direct first-through-seventh-order ACN/SN3D ambisonic output. Each voice selects a region of one shared AED terrain, scans a closed contour there, and uses that contour as its oscillator waveform.

The scan coordinates have two linked readings. Terrain height along the contour becomes sound, while each scan sample's longitude, latitude, and terrain height become azimuth, elevation, and distance. A voice therefore sounds and occupies the same place in the terrain model.

Workflow

1. Insert s3g Ambi Encoder Wave Terrain on a 64-channel REAPER track and select the ambisonic ORDER.
2. Follow it with an ambisonic decoder.
3. Use FREE mode for a sustained terrain oscillator bank, MIDI mode for note-triggered voices, or BOTH.
4. Use the FORM, SKIN, WARP, and READ terrain tabs to construct and interpret the surface.
5. Shape each contour with TRACE and its curved or polygon-specific controls.
6. Compose movement with the selection LAW, transition JOIN, time-field controls, and optional LISTEN mode.
7. Set the integer VOICES and AED projection controls.

Terrain Controls

Field Composition

TRACE chooses an Orbit, Lissajous, Rosette, Fold, or Polygon contour. RADIUS, ASPECT, ROTATE, and WARP shape curved traces. Polygon exposes SIDES, ROUND, STAR, and SKEW; discrete side changes generate a new table and use the normal table crossfade. Four higher table levels are reconstructed from progressively restricted harmonic sets with tapered cutoffs, keeping sharp facets, terraces, and corners cleaner as pitch rises.

MOTION: ROTATE is the factory behavior. It keeps voices active and moves each scan region continuously with independent saw-phase AZ RATE and EL RATE clocks measured in rotations per minute. Elevation continues through the far side of the sphere with the corresponding azimuth turn at each pole, producing a full rotation instead of a sinusoidal reversal. RATE DEV gives every voice a deterministic rate variation. Current and next contours remain continuously crossfaded, so this motion does not require a duration/rest score.

MOTION: FIELD selects the composed stochastic scheduler. LAW chooses Random, Series, Weight, Tendency, Markov, or Walk region selection. JOIN chooses link, neighbor merge, or local variation. Density, duration, rest, contrast, deviation, memory, transfer, and macro duration compose activity over time. XFADE controls its current-to-next table interpolation.

LISTEN makes the output field an internal score. Eight cube-corner virtual microphones decode the instrument's pre-output-gain ACN/SN3D field and retain a short directional memory. FOLLOW attracts region choice, Markov weighting, scan orientation, and activity toward recently active directions. COUNTER applies the same relationships to their antipodes. BALANCE favors underexposed directions. The response pulls continuously toward a target rather than teleporting a scan, and it also operates in ROTATE mode. OFF disables listener influence and uses the unmodified traversal.

Voice Model

VOICES is an integer from 1 to 64. There is no separate monophonic/polyphonic trigger selector; the selected voice mode and envelope controls determine the behavior.

FREE mode sustains the voice field. With PITCH: NOTE, BASE sets its center note. With PITCH: TRAVEL, BASE calibrates scan velocity and the measured 3D length of each contour determines frequency: larger or rougher paths take longer and sound lower. SCALE can leave that result Free or constrain it to the shared ordered 101-scale catalog also used by Ambi VOT and Ambi Vox. Quantization happens after contour measurement but before TUNE and per-voice DETUNE, preserving fine movement around each permitted pitch. SPREAD varies scan velocity across voices. MIDI mode retains incoming note pitch and uses the ADSR controls; BOTH layers both behaviors.

Spatial Model

Each voice is encoded into HOA at the center of its scan contour. Center longitude maps to azimuth, center latitude maps to elevation, and terrain height at that center displaces distance. The oscillator can therefore traverse the contour at audio rate without imposing audio-rate modulation on the spatial coefficients. AZIM, ELEV, and DIST set the formation center, SPACE scales its angular extent, and FOLLOW smooths center motion.

Display

TERRAIN VOICE FIELD uses neutral relief lighting for the shared surface. Every white line is an active waveform-reading contour moving across the terrain, and its bright point is the voice's actual AED center. Click anywhere along a contour to select its voice. The selected voice also shows faint cyan and magenta references for its current and next regions.

TERRAIN TO WAVEFORM places the sampled scan profile above the interpreted oscillator waveform. The profile begins with the contour's geometric carrier and morphs toward terrain height by DEPTH × RELIEF. A circular Orbit over a smooth sphere therefore produces a low-harmonic sinusoidal profile rather than retaining hidden terrain detail. Edge, Curvature, Ridge, and Valley are derived along the displayed profile. Gradient and Normal inspect the local two-dimensional surface, and Cross compares terrain on both sides of the trace.

Order and Routing

The output bus is 64 channels wide. The selected order activates the corresponding ACN channels and clears the remainder.