MBR model (modified Beeler-Reuter, Calcium dynamics speedup by 2).
2D spiral waves
On 2D plane Vm values are displayed by the red color.
2 x 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 time steps per frame.