Hi Ramana,

I think I know what you are trying to do; you are trying to get images
such as these:

http://ecotect.com/products/ecotect/features/solar

I was also struggling with this and now I believe the key is that you
*do not* use the Analysis Grid at all. Instead of calculating incident
solar radiation for the Analysis Grid after stretching it over a
surface, you calculate it for Selected Surfaces under the "What should
values be calculated for?" dialogue in the Solar Access Analysis wizard.
Before you do this, however, you need to break up the surface using the
Surface Subdivision module. You select the building and then go to
Modify, Surface Subdivision, Rectangular Tiles. This should allow you
to calculate radiation over a whole surface without worrying about
stretching the grid. There seems to be a limit as to how far around
something the grid can be stretched with the 3D Form Fit option.

Hope this helps,

Roselin Osser, LEED AP