On 2D plane positive u values are displayed by the red color
(negative "tail" is not shown). v values are displayed by the green
color. This script uses simple explicit algorithm and
512×512 float32 textures with the CLAMP_TO_EDGE
boundary conditions. It makes 2 it + 1 time steps per frame.
In 3 seconds the script begins to plot the path of the spiral wave tip.