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QuaScript

Alpha-Beta Velocity Ribbon

Admin's Choice NewFree

Alpha-beta tracker: level, velocity colour and tracking-error envelopes

WebGPU StudioPrice overlay WebGPU CanvasHybridDashboardSignalsAlerts
quascriptgpuwebgpukalmanvelocitytrend

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Language
QuaScript
Engine
Native C++, incremental on live ticks
Rendering
WebGPU + Canvas
Placement
Price overlay
Settings
4
Plots
8
Lines of code
62
Source
presets/analysis/gpu/velocity_ribbon.qs
Alpha-Beta Velocity Ribbonengine result
Loading the engine result…
quatick-charts · QuaScript engine on synthetic 1-minute bars · drag to pan · scroll to zoom · Run executes the script on the engine (⌘/Ctrl+Enter while editing)

About

A two-state tracking filter (alpha-beta, the steady-state form of a constant-velocity Kalman filter) follows price level and price velocity together. The level line is wrapped in two envelopes of the tracking error (one and two standard deviations), and the ribbon is coloured every bar by the velocity in ATR per bar on a cool-warm ramp: deep blue falling fast, white still, hot red rising fast. Because the filter predicts with its velocity, it turns earlier than a moving average of similar smoothness. Reading: a warm ribbon with price inside the inner envelope is a healthy trend; price outside the outer envelope is a shock the tracker has not absorbed yet. Velocity crossing zero is the turn; a velocity that keeps its sign while acceleration flips is a trend losing power. Signals: velocity turns up / down, shock outside the outer envelope, deceleration warnings.

8
Plotted series
4
Signal marks
1
Drawings
3
Alert rules
4
Settings
51
Lines of code

What it draws

Price overlay · counted from the engine's plot table and the script's draw calls

Series

  • Line1 visible · 7 helper
    Tracked level
  • Band fills (render.band calls)3
Legend
Tracked level

Signal marks

Velocity turns upVelocity turns downShockDeceleration

Drawings and chart effects

  • Dashboard tables1 created

How it runs

From source to the live chart, for this script

  1. 1
    Compile

    The QuaScript compiler checks the 62-line script (51 lines of code) and lowers it for the native C++ engine. Compile errors point at the exact line and column.

  2. 2
    Place

    The header sets overlay = true, so everything is drawn on the price chart, on the same scale as the candles.

  3. 3
    Compute

    The script runs once per bar, oldest to newest. 3 persist variables keep state (objects, counters) across bars.

  4. 4
    Stay live

    On the terminal the script keeps one live engine session: a tick rolls the forming bar back to its checkpoint and re-executes only that bar, and new bars are appended, so history is never rerun while the market moves. The live result is identical to a full run.

  5. 5
    Render

    The results are handed to the chart: series on WebGPU, drawings on the Canvas 2D QuaScript layer.

  6. 6
    Tune

    4 settings in 3 groups appear in the chart's settings dialog. Changing one reruns the engine with the new value.

Rendering

Hybrid: this script draws on 2 surfaces at once

WebGPUSeries renderer

The browser's modern GPU API. The chart uploads every line, band and mark of the script as GPU buffers and draws them in one pass, so dense heatmaps and dozens of series stay smooth while you pan and zoom. Without WebGPU support the chart's GPU layer falls back to WebGL 2, then Canvas 2D.

In this script
  • • 8 plotted series
  • • 3 band fill calls
  • • 4 signal mark types

Chosen by render = webgpu in the header.

WebGLNot used

GPU drawing through WebGL 2, available in every current browser. Used for chart-native profiles and for series that ask for it with backend = "webgl". Fast for large numbers of bars and wide fills.

CanvasUsed

The browser's 2D drawing API. Text-heavy and object-style output (dashboard tables, zones, tags, segments), candle colors and backgrounds are painted by the QuaScript layer, a Canvas 2D surface over the chart. Series use Canvas when the script's header does not ask for a GPU.

In this script
  • • 1 dashboard tables (QuaScript layer)

Alerts

3 alert rules declared with alert.rule

Velocity turns up

The tracked velocity crossed above zero

Velocity turns down

The tracked velocity crossed below zero

Shock

Close moved outside the two-sigma tracking envelope

Settings

4 settings, grouped as in the chart's settings dialog

Tracker
SettingTypeDefaultRange / optionsId
Alpha (level gain)Number0.180.01 – 0.9, step 0.01alpha_level_gain
Beta (velocity gain)Number0.0120.0005 – 0.5, step 0.0005beta_velocity_gain
Envelope
SettingTypeDefaultRange / optionsId
Error windowInteger505 – 1000error_window
Style
SettingTypeDefaultRange / optionsId
Velocity colour scale (ATR / bar)Number0.250.02 – 2, step 0.01velocity_colour_scale_atr_bar

Script

packages/quascript/presets/analysis/gpu/velocity_ribbon.qs

Header

analysis "Alpha-Beta Velocity Ribbon" {
    overlay = true
    render = webgpu
    short_title = ABV
    precision = 2
}
Total lines
62
Code lines
51
Comment lines
10
Helper functions
0
Loops
0
Persistent variables
3
Higher-interval feeds
0
Engine plots
8

Built with

Technical analysis (ta.*)
ta.atrta.ema
Statistics (stat.*)
stat.stdev
Math (math.*)
math.absmath.clampmath.is_namath.max
Imported modules
viz/premium

Discussion

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