Question about 3D Shade Calculator

I have a question regarding the shading model in SAM. I have used the 3D shade calculator to develop a 3d model of my system. And I have divided my subarrays into multiple strings. My question is that when there is shading on a string, does SAM assume that the shading will negatively impact the entire string? Or does it provide a linear analysis and only reduce the output of string by the % of the string that is shaded?
When your your 3D shading scene consists of separate active surfaces that you have identified to represent different strings, you can choose how SAM determines the shading loss on the subarray for each time step from the shading loss for each string in that time step. The options are described in SAM's help system. The database lookup option uses an empirical method based on measured data to make the conversion, while the other options either calculate the average of the string losses to apply to the subarray, or use the maximum or minimum of the string loss to apply to the subarray.

Best regards,

Paul.

One other thing to mention is that in SAM 2016.3.14 Revision 1, there is a bug that causes SAM to crash when you run a case with more than one subarray with beam irradiance shading enabled and the "database lookup" option for converting string losses to subarray losses. The issue is caused when you choose the database lookup option for one or more subarrays without enabling the option any of the remaining disabled subarrays in the system.
We will fix this issue in the next update, but until then, here is a workaround:

1. 
   On the System Design page, under DC Subarrays, click Enable for all four subarrays, including any that are not part of your system with zero strings allocated to the subarray.
2. 
   On the Shading and Snow page, under External Shading, for each of the four subarrays (including those that are not part of your system), click Edit Shading, check Enable beam irradiance shading losses by time step, and choose Database lookup as the method for converting string losses to subarray. (You do not need to change anything else, or populate the loss table for the subarrays that are not in your system.)
3. 
   Go back to the System Design page, and clear the Enable checkbox for any subarrays that are not part of your system.

When you click Simulate after following those steps, SAM should run and correctly apply the shading losses.
Alternatively, you can use one of the other options (average of strings, maximum of strings, or minimum of strings) instead of the database lookup option to avoid the problem altogether.
Best regards,

Paul.