uk.ac.starlink.ttools.plot2.geom

Class SinProjection

java.lang.Object

uk.ac.starlink.ttools.plot2.geom.SkyviewProjection

uk.ac.starlink.ttools.plot2.geom.SinProjection

All Implemented Interfaces:

Projection

public class SinProjection
extends SkyviewProjection

Sine (orthographic) projection. This is the one that gives you a rotatable sphere. North always faces directly up (is aligned along the screen Y direction). This is a singleton class, see INSTANCE.

Since:

21 Feb 2013

Author:

Mark Taylor

Field Summary

Fields

Modifier and Type	Field and Description
static SinProjection	INSTANCE Singleton instance.

Method Summary

Modifier and Type	Method and Description
SkyAspect	createAspect(boolean reflect, double[] r3, double radiusRad, Range[] vxyzRanges) Creates a SkyAspect from configuration information.
double[]	cursorRotate(double[] rot0, Point2D.Double pos0, Point2D.Double pos1) Attempts to return a rotation matrix corresponding to moving the cursor between two plane positions.
SkyFov	getFov(SkySurface surf) Returns the field of view represented by this aspect.
boolean	isContinuous() Indicates whether this projection is known to be continous over its whole range.
boolean	isContinuousLine(double[] r3a, double[] r3b) Indicates whether a line between the two given sky positions is (believed to be) continuous.
boolean	project(double rx, double ry, double rz, Point2D.Double pos) Overridden for slight efficiency gain.
double[]	projRotate(double[] rot0, Point2D.Double pos0, Point2D.Double pos1) Attempts to return a rotation matrix that will transform a sky position from one plane position to another.
boolean	useRanges(boolean reflect, double[] r3, double radiusRad) Indicates whether ranges should be provided to generate a SkyAspect.
static double[]	verticalRotate(double delta, double alpha, boolean reflect) Rotation matrix which results in an orientation with the viewing plane X coordinate of the north pole equal to zero.

Methods inherited from class uk.ac.starlink.ttools.plot2.geom.SkyviewProjection

getProjectionDescription, getProjectionName, getProjectionShape, getSkyviewProjecter, unproject

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INSTANCE

public static SinProjection INSTANCE

Singleton instance.

Method Detail

project

public boolean project(double rx,
                       double ry,
                       double rz,
                       Point2D.Double pos)

Overridden for slight efficiency gain.

Specified by:

project in interface Projection

Overrides:

project in class SkyviewProjection

Parameters:

rx - normalised 3D X coordinate

ry - normalised 3D Y coordinate

rz - normalised 3D Z coordinate

pos - point object into which projected dimensionless X,Y coordinates will be written on success

Returns:

true if transformation succeeded

isContinuous

public boolean isContinuous()

Description copied from interface: Projection

Indicates whether this projection is known to be continous over its whole range. Returns false if there may be any cases for which isContinuousLine returns false.

Returns:

true iff this projection is known to be continuous

isContinuousLine

public boolean isContinuousLine(double[] r3a,
                                double[] r3b)

Description copied from interface: Projection

Indicates whether a line between the two given sky positions is (believed to be) continuous. "Line" in this context should ideally be interpreted as the shorter arc on a great circle. A line crossing lon=180 for instance would be discontinuous in an Aitoff projection, but not in a Sin projection.

Parameters:

r3a - 3-element array giving normalised X,Y,Z coordinates of line start

r3b - 3-element array giving normalised X,Y,Z coordinates of line end

Returns:

true if line is believed to be continuous; if in doubt, probably better to return true

cursorRotate

public double[] cursorRotate(double[] rot0,
                             Point2D.Double pos0,
                             Point2D.Double pos1)

Description copied from interface: Projection

Attempts to return a rotation matrix corresponding to moving the cursor between two plane positions. Ideally this should do the same thing as projRotate, for both positions on the sky, and provide some other intuitive behaviour if one or both is out of the projection range.

Null may be returned if this projection does not support rotation.

Parameters:

rot0 - initial rotation matrix

pos0 - initial cursor position

pos1 - destination cursor position

Returns:

destination rotation matrix, or null

projRotate

public double[] projRotate(double[] rot0,
                           Point2D.Double pos0,
                           Point2D.Double pos1)

Description copied from interface: Projection

Attempts to return a rotation matrix that will transform a sky position from one plane position to another.

Consider a sky point S, rotated by an initial rotation matrix rotmat to S', which when projected by this projection lands on the plane at pos0. This method attempts to determine a rotation matrix which when used instead of rotmat would end up with the rotated and projected point at pos1.

Null may be returned if this projection does not support projection.

Parameters:

rot0 - initial rotation matrix

pos0 - initial projected position

pos1 - destination projected position

Returns:

destination rotation matrix, or null

useRanges

public boolean useRanges(boolean reflect,
                         double[] r3,
                         double radiusRad)

Description copied from interface: Projection

Indicates whether ranges should be provided to generate a SkyAspect. If supplied field of view arguments are sufficient, or if a default aspect is always produced, return false.

Parameters:

reflect - whether requested aspect will be reflected

r3 - central position of field of view (may be null)

radiusRad - radius of field of view (may be NaN)

Returns:

true if ranges would be useful given the other arguments

See Also:

SurfaceFactory.readRanges(P, uk.ac.starlink.ttools.plot2.PlotLayer[], uk.ac.starlink.ttools.plot2.data.DataStore)

createAspect

public SkyAspect createAspect(boolean reflect,
                              double[] r3,
                              double radiusRad,
                              Range[] vxyzRanges)

Description copied from interface: Projection

Creates a SkyAspect from configuration information. Either the supplied field of view or data ranges may be used, or neither.

Parameters:

reflect - whether requested aspect will be reflected

r3 - central position of field of view (may be null)

radiusRad - radius of field of view (may be NaN)

vxyzRanges - definite ranges for normalised X,Y,Z coordinates acquired from data

Returns:

new sky aspect

See Also:

SurfaceFactory.createAspect(P, uk.ac.starlink.ttools.plot2.config.ConfigMap, uk.ac.starlink.ttools.plot.Range[])

getFov

public SkyFov getFov(SkySurface surf)

Description copied from interface: Projection

Returns the field of view represented by this aspect. This is a best estimate, it may be approximate depending on the projection geometry. If the field of view is the default for this projection, then null should be returned. Null may also be returned if for some reason no field of view can be determined.

Parameters:

surf - sky surface, which must be set up using this projection

Returns:

field of view, or null

verticalRotate

public static double[] verticalRotate(double delta,
                                      double alpha,
                                      boolean reflect)

Rotation matrix which results in an orientation with the viewing plane X coordinate of the north pole equal to zero. This is a rotation invariant we wish to preserve.

Parameters:

delta - rotation of pole from vertical (0..pi)

alpha - rotation around pole (0..2pi)

reflect - if true, alpha increases right to left

Returns:

rotation matrix