I am doing a bird’s eye view of my scene. I don’t know how to make the sun lamp cast cloud shadows.
Just add a clouds texture to the lamp. That will vary the light intensity of the lamp. You can use images as well as procedural. These are often called ‘gobos’.
So it was just that simple by the way.
Also, and in addition to the above, look at “shadow-only spotlights” which generate shadows but not light. If you need a sun-lamp to “cast a shadow,” use a shadow-only spot to generate an appropriate shadow pass.
It’s a good idea to treat “shadows” as a form of “light.” A shadowless lamp is cheap and fast; shadows are what takes the time. And, shadows in a scene usually need to be simplified for maximum impact. Whereas a real-world photographer has to monkey-around with the lights to subdue the unwanted shadows, you can “magically” produce a base scene with no shadows at all, then inject the shadows that you want into it, and finally, fine-tune the blending of the shadow-data into the finished picture. (Modulating it with a cloud-texture, for instance …)
"CG: the Perfect Digital Darkroom. What I just described is a technique that cannot exist in the real world. But, the good news is, this isn’t the real world!