Stretch Transform

Stretch Transform is a geometric transformation that distorts a plane or 3D space in a rubbery way.

For a more detailed explanation of this project read this on my website.

Quick start

1. Install the library:

Via NPM:

npm i stretch-transform

Or in your html file:

<script src="StretchTransform.js"></script>

2. Start creating a new StretchTransform:

var myTransform = new StretchTransform();

3. Add some anchors.

Usually you'll give two points as parameters. The first point (origin) will be transformed exactly to the second point (target).

myTransform.addAnchor([100, 200], [300, 300]);

If you give only point as a parameter origin and target will be set to that position. You could change either of them later on.

myTransform.addAnchor([100, 200]);

StretchTransform also works in 3D space. In fact, it always does.

myTransform.addAnchor([100, 200, -150], [300, 300, 0]);

4. Transform any point you want.

var result = myTransform.transform([200, 200, 50]);

Reference

Table of Contents

• StretchTransform
  • addAnchor
  • addAnchor
  • removeAnchor
  • removeAnchor
  • getAnchorCount
  • getAnchor
  • getAnchorByPos
  • getAnchorByOriginPos
  • getAnchorByTargetPos
  • getAnchorOrigin
  • setAnchorOrigin
  • getAnchorTarget
  • setAnchorTarget
  • getWeightingExponent1
  • setWeightingExponent1
  • getWeightingExponent2
  • setWeightingExponent2
  • transform
  • updateAnchorMatrices
• Anchor
  • getOriginPosition
  • setOriginPosition
  • getTargetPosition
  • setTargetPosition
  • getTransformMatrix

StretchTransform

new StretchTransform() creates an empty StretchTransform.

addAnchor

Adds an Anchor where origin and target is the same. You can change either of them later on.

Parameters

• p Array Array [x, y, z] that will be used for origin and target position. Z coordinate is optional.

Returns Anchor The new anchor

addAnchor

Adds an Anchor. pOrigin will be transformed to pTarget.

Parameters

• pOrigin Array Array [x, y, z] for the origin position. Z coordinate is optional.
• pTarget Array Array [x, y, z] for the target position. Z coordinate is optional.

Returns Anchor The new anchor

removeAnchor

Removes an Anchor giving the anchor

Parameters

• anchor Anchor Anchor to remove

removeAnchor

Removes an Anchor giving the index of the anchor.

Parameters

• i Number Index of the anchor

getAnchorCount

Returns Number of anchors added to the MultiTransform

getAnchor

Parameters

• i Number Index of the anchor to return.

getAnchorByPos

Parameters

• p Array point [x, y, z] to search for an anchor (either origin or target position). Z coordinate is optional.
• tolerance Number Radius around Anchor

Returns Number Index of the found anchor or -1 if nothing was found at the specified position

getAnchorByOriginPos

Parameters

• p Array point [x, y, z] to search for the origin position of an anchor. Z coordinate is optional.
• tolerance Number Radius around Anchor

Returns Number Index of the found anchor or -1 if nothing was found at the specified position

getAnchorByTargetPos

Parameters

• p Array point [x, y, z] to search for the target position of an anchor. Z coordinate is optional.
• tolerance Number Radius around Anchor

Returns Number Index of the found anchor or -1 if nothing was found at the specified position

getAnchorOrigin

Parameters

• i Number Index of the anchor.

Returns Array The origin position.

setAnchorOrigin

Parameters

• i Number Index of the anchor.
• p Array New origin position [x, y, z]. Z coordinate is optional.

getAnchorTarget

Parameters

• i Number Index of the anchor.

Returns Array The target position.

setAnchorTarget

Parameters

• i Number Index of the anchor.
• p Array New target position [x, y, z]. Z coordinate is optional.

getWeightingExponent1

Returns Number

setWeightingExponent1

Exponent of the weighting function. Defines how the relations from one anchor to all others are cumulated. The closer the other anchor lies, the stronger it is weighted.

Parameters

• val Number Usually something between 0 and 2. Default = 1.

getWeightingExponent2

Returns Number

setWeightingExponent2

Exponent of the weighting function when applying all anchor matrices to a point.

Parameters

• val Number Usually 1 or higher. Default = 2.

transform

Main function of the class. Transforms a point on the plane and returns its new position.

Parameters

• p Array Point given as an Array [x, y, z] to be transformed. Z coordinate is optional.

Returns Array Transformed point as an Array.

updateAnchorMatrices

It's usually not necessary to call this method. If anchors and parameters are always set with the given methods (setAnchorOrigin(), ...), this method will be called automatically. It calculates a transformation matrix for each anchor. This matrix reflects the translation of the anchor and the rotation and scaling depending on the (possibly) changed positions of all other anchors.

Anchor

An Anchor has an origin an a target position. Usually you won't have to deal with it directly. Still, there are some functions which could come handy.

Parameters

• pOrigin
• pTarget

getOriginPosition

Returns Array The origin position.

setOriginPosition

Parameters

• p Array New origin position [x, y, z]. Z coordinate is optional.

getTargetPosition

Returns Array The target position.

setTargetPosition

Parameters

• p Array New target position [x, y, z]. Z coordinate is optional.

getTransformMatrix

Returns Array The transformation matrix of this anchor.