Shadow Softness for Sunlight?

KickAir 8P

If (aside from low-intensity fill lights) I'm making cloud-free sunlight from a Distant Light using raytraced shadows, what's the most realistic Shadow Softness number?

In the two renders below, the one with the woman walking to her car has no shadow softness, and (of course) the shadows of the palm-fronds are too hard. In the Hulk'n'TonyBear render the shadow cast in front of him is from the broken roofline of a tall building, and although I think the shadows are too soft, since I don't have any tall buildings (or sunlight - it's cloudy here) to check against I can't tell if 0.50% is too much.

Is there an official this-is-the-Shadow-Softness-for-sunlight number? If not, what are you-all's preffered settings?

Richard Haseltine

Bright sunlight is pretty sharp - vegetation usually casts softer shadows because it's moving, not because the shadows are inherently soft. It think there's also often some refraction (or is it diffraction) around the leaf edges. In DS4.5 you might try adding a touch of motion blur to the plants - I'm not sure if that would work or not. \You could also add some noise displacement to the driveway - and for that matter, does it have any displacement for the gaps between bricks?

millighost

The sun is 150 Million km away and has a diameter of 1.3 million km. So the diameter of the penumbra would follow the same ratio, i.e. the penumbra of an object 150 meter away would have a diameter of 1.3 meter. In other words the radius of the blur is 1.3/150 = 0.0086 = approx. 0.9%

ReDave

Heh, good point! 'Should be "diameter" in your last sentence, though. Going to experiment sometime if some Sun would deign to show itself...

Richard Haseltine

The atmosphere will also add some blurring, depending on thickness, humidity perhaps, and dust.