Interface Projection

All Known Implementing Classes:
FixedSkyviewProjection, HemisphereProjection, SinProjection, SkyviewProjection

public interface Projection
Sky projection. Defines the mapping of normalised X,Y,Z coordinates (direction cosines) to dimensionless coordinates on a 2D plane.
Since:
21 Feb 2013
Author:
Mark Taylor
  • Method Summary

    Modifier and Type
    Method
    Description
    createAspect(boolean reflect, double[] r3, double radiusRad, Range[] vxyzRanges)
    Creates a SkyAspect from configuration information.
    double[]
    cursorRotate(double[] rotmat, Point2D.Double pos0, Point2D.Double pos1)
    Attempts to return a rotation matrix corresponding to moving the cursor between two plane positions.
    Returns the field of view represented by this aspect.
    Returns a short description of the projection.
    Returns the projection name.
    Returns the shape which encloses all the plane positions to which legal sky coordinates can be projected.
    boolean
    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)
    Transforms a sky position to a plane position.
    double[]
    projRotate(double[] rotmat, 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
    unproject(Point2D.Double pos, double[] r3)
    Transforms a plane position to a sky position.
    boolean
    useRanges(boolean reflect, double[] r3, double radiusRad)
    Indicates whether ranges should be provided to generate a SkyAspect.
  • Method Details

    • getProjectionName

      String getProjectionName()
      Returns the projection name.
      Returns:
      user-directed projection name
    • getProjectionDescription

      String getProjectionDescription()
      Returns a short description of the projection. return projection description
    • isContinuous

      boolean isContinuous()
      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

      boolean isContinuousLine(double[] r3a, double[] r3b)
      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
    • project

      boolean project(double rx, double ry, double rz, Point2D.Double pos)
      Transforms a sky position to a plane position.
      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
    • unproject

      boolean unproject(Point2D.Double pos, double[] r3)
      Transforms a plane position to a sky position.
      Parameters:
      pos - contains dimensionless X,Y coordinates of plane position
      r3 - 3-element array into which normalised X,Y,Z sky coordinates will be written on success
      Returns:
      true if transformation succeeded
    • getProjectionShape

      Shape getProjectionShape()
      Returns the shape which encloses all the plane positions to which legal sky coordinates can be projected. Typically this has linear dimensions of the order of PI.
      Returns:
      projected sky shape
    • cursorRotate

      double[] cursorRotate(double[] rotmat, Point2D.Double pos0, Point2D.Double pos1)
      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:
      rotmat - initial rotation matrix
      pos0 - initial cursor position
      pos1 - destination cursor position
      Returns:
      destination rotation matrix, or null
    • projRotate

      double[] projRotate(double[] rotmat, Point2D.Double pos0, Point2D.Double pos1)
      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:
      rotmat - initial rotation matrix
      pos0 - initial projected position
      pos1 - destination projected position
      Returns:
      destination rotation matrix, or null
    • useRanges

      boolean useRanges(boolean reflect, double[] r3, double radiusRad)
      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:
    • createAspect

      SkyAspect createAspect(boolean reflect, double[] r3, double radiusRad, Range[] vxyzRanges)
      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:
    • getFov

      SkyFov getFov(SkySurface surf)
      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