depends on varions things. if the obstical is just a block in a single room won't effect it as say 2 seperate room blosk with a path between. the obstical a bock or a map entity/model? the 2 later won't effect it ( actualy increase the face rendering so lowering frames more)

don't use the Detail check box as it makes it soemthing 'transparent' far as blocking rendering view is concerned. so a detailed block is ignored in deterining what to render within the POV.

# of faces (poly count) per mdl effects fps as well because blocks are processed during build time for rendering, lighting,shadows. models are redered at runtime within POV and cliprange