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BPF and BPC Tools

This section details a set of important concept and tools. Among these, a number of function boxes allow to build or manipulate BPFs and BPCs. To access these tools, go to Functions / Basic Tools / Curves & Functions.

Online Documentation Reference

The online function reference provides more detailed information about the following (and more) functions, as well as different arguments. To refer to it, select a function and press d.

Getting Coordinates : Transfer and Point Coordinates

Point-Pairs : Points of the Curve

The ** point-pairs ** function returns the points of the curve as a list of (x y) coordinates.

Point-pairs : list of (x y) points in the curve.

Transfer : Selected Points

Two transfer tools return the values of points that are not explicitly given in the curve.

• **” X-transfer” ** returns the ordinates for a given abscissa.

• **” Y-transfer” ** returns the abscissa values corresponding to given ordinates.

Transfers : x-transfer returns the y-coordinate for x=5. Y-transfer returns the various abscissa for y=20.

Sampling a Curve : Om-Sample

Sampling consists in creating a new curve of n regularly sampled points, out of an initial set of points.

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Inputs

The om-sample function has two default inputs :

• “self” : a list of points, BPF or BPC objects.

• “sample-rate” : a number of samples in integers, or a sample-rate in floats.

It has three optional inputs :

• “x-min” and “x-max” define a segment to sample within the curve.

• “decimals” :

The sampling rate can be expressed as a float input to Om- samplezoom

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“sample-rate” input : Integer or Float

Be a curve whose min = 0 and max = 100.

• Integer : n = 20 we get 20 points, whose values are (0 5 10 15 20 25 30 35 …. 100).
• Float : SR = 20.0, we get 5 points, whose values are (0 20.0 40.0 60.0 80.0 100.0).

In any case n = (xmax - xmin) / SR

Outputs

Om-sample returns 3 values :

• a sampled object, such as a BPF , BPC …
• a list of x -coordinates
• a list of y -coordinates

Up-Sampling and Down-Sampling

If n is lower than the initial number of points, curves are down-sampled. If n is higher, curves are up-sampled.

Splines : Om-Spline

Splines are mathematical functions defined piecewise by polynomial interpolation. They are used for generating smoothed interpolated shapes , starting from a set of control points.

The ** om-spline ** function generates spline curves starting from the points of a BPF or BPC.

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Inputs

• “resolution” : a number of points in the spline preview.

• “degree” : a number of adjacent control points used for computing the spline curve points. Higher values produce smoother curves.

Outputs

The three outputs of om-spline return :

• a spline object (BPF, BPC…)

• a list of x-coordinates

• a list of y-coordinates

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Spline Preview

The BPF and BPC editors allow to visualize a preview of the output spline object.

Spline Preview in the BPF/BPC Editors.

• Display Options

References :

Contents :

• OpenMusic Documentation
• OM User Manual
  • Introduction
  • System Configuration and Installation
  • Going Through an OM Session
  • The OM Environment
  • Visual Programming I
  • Visual Programming II
  • Basic Tools
    • Curves and Functions
      • BPF / BPC
      • BPF/BPC-Libs
      • Editors
      • BPF / BPC Tools
      • 3D Objects
    • Array
    • TextFile
    • Picture
  • Score Objects
  • Maquettes
  • Sheet
  • MIDI
  • Audio
  • SDIF
  • Lisp Programming
  • Errors and Problems
• OpenMusic QuickStart

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