DotOffset - aleslab/Psychtoolbox-3-aleslab-fork GitHub Wiki

[dx,dy,dz,a,e] = DotOffset(r,d,ndots)
computes DX, DY and DZ offsets to move a point in a direction specified
by R. Output for NDOTS offsets are computed independently. Only azimuthal
direction can be specified or both azimuth and elevation, in which case a
number of different randomizations are possible (see third form of R
below). D is the distance by with dots are to be offset and should be
either scalar or have length NDOTS.

all angles are in degrees

Outputs A and E are the azimuth and elevation angles used by DotOffset
for each offset. If only one output is requested, a 3xNDOTS output matrix
with the x, y and z offset on the respective rows is returned.

R can take four forms:

• scalar: direction (in degrees) of offset in azimuth (0 is translation
  in z direction, 90 in x direction towards 3 o'clock), used for all
  outputted offsets
• vector with length NDOTS: direction (in degrees) of offset in azimuth
  specified in input for each outputted offset
• a matrix of size NDOTSx2: direction (in degrees) of offset in azimuth
  (first column) and elevation (second column) specified in input for
  each outputted offset
• 2x2 cellmatrix: the first row specifies azimuth direction, the second
  the elevation angle. A number of different inputs for the azimuth and
  the elevation row are possible and lead to the following outputs:
  • first column is a vector with length NDOTS: direction (in degrees) of
    offset specified for each outputted offset. Second column is ignored.
  • first column is a vector with length other than NDOTS: for each
    outputted offset, offset direction is randomly selected from the
    values in the vector (see 'help RandSel'). Second column is ignored.
  • scalar in the first column and NaN in the second column (e.g.
    {45,NaN;67,NaN} or {45,90;67,NaN}). Direction specified in the first
    column is used for all outputted offsets.
  • scalar in the first and second column (both non-NaN)) (e.g.
    {45,90;67,NaN} or {45,90;0,360}). For each offset, a random direction
    is chosen within the specified limits. Angles are randomly chosen
    between lower (1st column) and upper (2nd column) boundaries (see
    'help RandLim').

Function can also be used to compute points laying on (part of) a Circle
or sphere with radius D:
[X,~,Z] = DotOffset(linspace(0,360),D,100);