Hi,@ahad For Q1, there is no good value for all scenario.For masterplan phase, you can set a big grid-size to generate corse result quickly. If you want to get smooth result, you should set a small grid-size. And small grid-size will take more time to finish the calculation.
Here is a demo

In this pitcutre, there are 2280 grid on the shape.

For Q3, In my experience, for masterplan phase, you can set grid-size as 5 meter. For detailed analysis, you can set grid-size as 0.5 meter or smaller.

like as you know: (No. grid * average grid size = area of shape)
but with respect to below picture:
No. grid=7379
average grid size = 0.06 m2
total area=7379*0.06=442.74 m2
but my total area is just 18.2 m2. (i calculated area by rhino and i created my shape in rhino too.)

@AbrahamYezioro
in the above picture, what is the unit of gridsize?? meter or meter square??
if it is meter square,
0.0025…0.05 multiplied by 0.05
in this way 0.05 and 0.06 are so close.

I really don’t understand what is the issue here.
The grid size input is a wishful thinking setting. Since LB/HB is using GH meshing algorithms it doeasn’t guarantee that each grid size will fit the setting.
This setting should be given according to the model units. So if you work in mts give it in mts, and so on.
-A.