Please help.. Archviz

I have a big problem with Shadows… I cant understand what problem is.

in Sample scene, my shadows are pretty good but when i start with a blank scene my shadows are very bad and its not realistic…

for example, Sun shines is entering from window hole. ( Window’s shape is like Rectangle) but shadows are as a circle… whats the problem?

OR very easy, simple model i have, and this model 's shadow is very funny again… Light maps is true i know because in Sample scene my same model’s shadow is good , other one is bad…

which settings are Wrong ?

Please , I need some Help…

Sorry my English

Lightmap resolution of the floor mesh is too low.

Also, don’t construct a floor out of multiple rectangular meshes, you will have issues that way