Pattern Spatial Waveform
The Grating Pattern, Radial Bars Pattern, Concentric Circles Patternand Looming Dots Pattern all map two-dimensional space onto a one-dimensional waveform. The Spatial Waveform parameter gives you a great deal of flexibility in specifying this one-dimensional waveform.
As a first step, you can choose between a basic sine, square, triangle, or ramp wave.
Then, you can scale and distort the basic wave using the Amplitude, DC Offset, Phase, and Symmetry parameters. Finally, you can continuously drift the waveform's phase using the Drift Freq. parameter, giving rise to dynamic effects like drifting gratings and looming circles.