[esp-r] Doubts about obstructions/shading

[Paulo Tavares]

Dear all,

I have two doubts about obstructions/shading in my model.

The first one is when i made a simple block representing an adjacent 
building i receive the next message:

FAILURE: in ../zones/z1.geo: *block_start, 0 0
     the opq grid X value (0) < allowable minimum 4!
FAILURE: in ../zones/z1.geo: *block_start, 0 0
     the opq grid Z value (0) < allowable minimum 4!

What could be the reason for this? How can i solve it?

The other doubt is how i model the building self-shading? My model is a 
cube but has a "hole" (courtyard) at the center.

Regards,

Paulo Tavares