I did a simple scene and both Poser4 and firefly failed giving almost the same render. The scene is a simple plane (big box) illuminated from behind with a directional light at 45 degrees. The green lines are cylinders indicating the incident and reflected ray from the plane. The reflected ray should have illuminated the small box making it visible, but it didn't! I agrre with the result of Poser4, Poser4 cannot do this, but raytracing (firefly) should have done!! The bounce number was set to 4, enough for the only two bounces that exist in the scene.

Stupidity also evolves!