No shadows from blinds coming through inside

hi guys so I have an annoying problem I just cant seem to figure out, im lighting my scene from outside with a sun lamp and shining it through the window which has blinds across it, im trying to achieve the shadows from the blinds coming down on the desk but all it does is shine bright on the desk with no hint of the shadows, ive tried mesh lights, point, sun, area all from different distances with no luck, I switched to renderman to see if it were just cycles and renderman works fine, anyone know the trick to get it to work in cycles??

Renderman lighting

cycles lighting

Try changing the size property of your sun lamp to 0

Your sun lamp size is too big. Somewhere between .02 and .08 is the realistic range for the sun, depending on the time of day you’re aiming for.

the default of 0.1 is waay too big for a bright and sunny day! 0.01 comes alot closer. 0.1 might work for recreating a dim sun that has to fight through hazy fog.
I did several shots where i had to match the CG to a plate and a setting of 0.01 matched pretty much perfect in most cases. I can’t remember where i initially read that but i think someone here in the forum did the math and recommended the 0.01 value. I am sticking with that since quite a long time now.