In a grid map, the PES is constructed in the same way a field is ploughed: A line is generated, left to right. At the end of the line, a step is taken in the other direction, then a line is generated right to left. Another step is taken, and the process continued until the "field" is "ploughed". The effect of SMOOTH is to plough the field again, in reverse, then to plough it twice more, at 90 degrees to the original direction. For each point, four separate calculations are done, one for each ploughing. The point with the lowest energy is then used.
In a path map, after the path has been generated, the direction is reversed, and the path re-calculated. As with the GRID map, the lower energy conformer is used at each point.
A limitation of SMOOTH is that the calculation must be run without using RESTART.
Without "SMOOTH":
>____________________
_____________________|
|_____________________
_____________________|
|_____________________
_____________________|
|_____________________
<____________________|
With "SMOOTH", the following grids are also used:
Grid 2
<____________________
_____________________|
|_____________________
_____________________|
|_____________________
_____________________|
|_____________________
>____________________|
Grid 3
___ ___
___
v | | |
| | | ^
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
|__ | |__ | |__ |
|__ |
Grid 4
___ ___
___
^ | | |
| | | v
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
|__ | |__ | |__ |
|__ |