newDots = bvlTrapezoidDots(dots, strDir, delta)
Trapezoidal transform of dots in the given direction by the specified amount.
dots - [
Nx2] array of dots to be translated. First column is the x
coordinate, Second Column the y coordinate.
[x1 y1; x2 y2; .... xN yN];
strDir - string specifing the direction
'top_forward', 'top_back', 'right_forward', 'right_back'
delta - amount to translate
newDots - [
Nx2] translated array
NOTE: Origin is at top-left of screen.
Psychtoolbox/PsychGLImageProcessing/private/bvlTrapezoidDots.m