Google cardBoard Android API (五)：Distortion

public class Distortion

Defines all required parameters to correct the distortion caused by the lenses.

Public Constructors

Distortion()

Distortion(Distortion other)

Public Methods

staticDistortion	cardboardV1Distortion()
float	distort(float radius)
float	distortionFactor(float radius)
boolean	equals(Object other)
Distortion	getApproximateInverseDistortion(float maxRadius, int numCoefficients)
float[]	getCoefficients()
void	)]setCoefficients(float[] coefficients)
String	toString()

Inherited Methods

▸From class java.lang.Object

Public Constructors

public Distortion ()

public Distortion (Distortion other)

Constructs a copy of another distortion object.


Parameters

other	The distortion object to copy from.

Public Methods

public static Distortion cardboardV1Distortion ()

Return distortion parameters for Cardboard v1.0.0.

public float distort (float radius)

Distorts a radius by its distortion factor from the center of the lenses.


Parameters

radius	Radius from the lens center in tan-angle units.

Returns

The distorted radius in tan-angle units.

public float distortionFactor (float radius)

Returns the distortion factor of a point.


Parameters

radius	Radius of the point from the lens center in tan-angle units.

Returns

The distortion factor. Multiply by this factor to distort points.

public boolean equals (Object other)

Compares this instance with the specified object and indicates if they are equal.


Parameters

other	The object to compare this instance with.

Returns

true

if the objects are equal,

false

otherwise.

public Distortion getApproximateInverseDistortion (float
maxRadius, int numCoefficients)

Builds an inverse-distortion object with least-squares-fitted coefficients.

This is intended for implementing application-side custom distortion. Use .getCoefficients() on the returned object to retrieve the inverse distortion function's coefficients.

This is an approximate inverse, and using .distort() on the returned object will be faster but less accurate than using the distortInverse() method on the original. For useful results, the input distortion must be well-behaved in the 0..maxRadius range.

Example for 50 degree half-angle FOV (100 degrees total), this will create an inverse distortion where inverse.distort(r) approximately equals distortion.distortInverse(r) in the range r = 0 ... maxFovHalfAngle.

float maxFovHalfAngle = 50.0f * Math.PI / 180.0f;
float maxRadiusLens = distortion.distortInverse(maxFovHalfAngle);
Distortion inverse = distortion.getApproximateInverseDistortion(
maxRadiusLens, 6);

Parameters

maxRadius	Maximum supported radius in tan-angle units in lens space (after applying barrel distortion). Should be set to inverseDistort(tan(maximum expected FOV angle)) to create an inverse that will be usable for inputs up to tan(maximum expected FOV angle).
numCoefficients	Number of desired coefficients, more provide a better fit. Does not need to match the number of coefficients in the input distortion object. 6 coefficients recommended for current Cardboard devices, using more can get numerically unstable.

Returns

New distortion object.

public float[] getCoefficients ()

Returns the current coefficients for lens distortion correction.


Returns

A floating point array with the current barrel distortion coefficients.

public void setCoefficients (float[] coefficients)

Sets the coefficients for lens distortion correction.

The coefficients Ki correspond to the pincushion distortion equation:

p' = p (1 + K1 r^2 + K2 r^4 + ... + Kn r^(2n))

Where r is the distance from the optical center, p the input point and p' the output point.


Parameters

coefficients	Barrel distortion coefficients to set.

public String toString ()

Returns a string containing a concise, human-readable description of this object.


Returns

A printable representation of this object.