Jagged shadows using sunlight

[3doutlaw]

I've got this problem with a sunlight that produces jagged shadows. On here I've found 2 posts, that are older. They are:

http://www.luxrender.net/forum/viewtopic.php?f=16&t=4554&p=47926&hilit=shadow+mesh#p47926

http://www.luxrender.net/forum/viewtopic.php?f=16&t=6743&p=68883&hilit=shadow+mesh#p68883

I did not really see a fix in those, except maybe subdivide or materials? Is this just a material issue?

I am using both LuxrenderDS from Daz Studio and Pose2lux from poser with the same model/maps, same issue. Seems to happen when the sunlight is increased.

Any thoughts/ideas?

[jeanphi]

Hi,

That's the main limitation of using normal interpolation over faceted geometry instead of truly smooth geometry. If you have strongly directional lighting, there's a point where interpolating the normal won't do because the next faces simply won't receive any light. Add some fill light to attenuate the issue or subdivide more.

Jeanphi

[bighouse]

I see this quite a bit when using Poser figures. If this was my scene, I would start with two levels of subdivision on the head and work up from there. Remember, you don't have to subdivide the entire model, just the part that is giving you problems.

[3doutlaw]

Thanks for the replies! I will work with it some more.

[Rhys]

I wonder if it is possible theoretically to implement normal smoothing in a method like microdisplacement, or perhaps this still has the problem?

[jeanphi]

Hi,

It would be possible to do that and overcome the issue but with a severe speed tradeoff, the algorithm is even documented in the paper used to implement microdisplacement in LuxRender.

Jeanphi

[sphere]

Another possible workaround is to increase the sun size by a factor k (with, say, k in the range 10-25). This will give you smoother shadows in all your scene.
Keep in mind that, in this case, the sun light intensity (or gain) must be reduced by a factor k^2 to keep the same lighting effect .