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Subsurface not working in shadows....

I have been putting together a grass material, and my results so far are what I'm looking for. The problem is when a shadow is cast onto the grass it appears that there is no subsurface effects. Any ideas on what could be causing this?

This is what it looks like with no shadows on it.

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This is what a shadow looks like from a distance.

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This is the comparison up close.

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I apologize for the low res images.....really!? 5.2 MB is a pretty low limit. This is a full shadow shot.

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It's not as easy to see it in the pictures.....but it looks horrible. There are black areas and its almost as if all of the color has been taken out of it. I think the black areas are being caused by my normal, but I can't figure out why. I'm not a big fan of posting my materials, but here are the relevant parts.

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Any help would be appreciated :)

Product Version: UE 4.11
no shadows.jpg (826.7 kB)
comparison shot.jpg (751.5 kB)
full shadow.jpg (551.1 kB)
material.jpg (464.6 kB)
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asked May 02 '16 at 10:07 AM in Using UE4

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A better image showing the issue would be great. However SSS will only work when the surface is directly lit because it's calculating how much light passes through when the light source is on the other side of the surface. If there is no light source visible then you won't see SSS. Light probes provide a generic, surrounding light environment so they can't be used in the calculation even if they are present.

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answered May 02 '16 at 11:31 AM

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avatar image worldlearner0411 May 02 '16 at 03:21 PM

Now that its a comment I can apparently post another 5mb :) This one is a high resolution.

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avatar image worldlearner0411 May 02 '16 at 03:34 PM

Subsurface not working without the direct lighting I guess makes sense. What would you recommend doing to resolve the issue? I have noticed that when I turn subsurface off altogether that I get a similar look....perhaps its just showing what my material looks like without subsurface? So in order to troubleshoot it I should work on getting it to look good without subsurface before adding it for the lit areas. What are your thoughts on this?

avatar image ZoltanE May 02 '16 at 04:41 PM

I'd add a very faint green emission to make the dark areas less ugly. Of course it will increase brightness of lit grass too so you might want to darken the diffuse color to compensate. It would be nice to apply this emissive only to pixels in shadow but I don't know any nodes which would get that information. (The LightVector doesn't work in the Surface material domain.)

avatar image worldlearner0411 May 02 '16 at 06:24 PM

Simple Material with no emissive properties...

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avatar image worldlearner0411 May 02 '16 at 06:24 PM

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simple material.jpg (501.3 kB)
avatar image worldlearner0411 May 02 '16 at 06:26 PM

Now with emissive......

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avatar image worldlearner0411 May 02 '16 at 06:27 PM

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avatar image worldlearner0411 May 02 '16 at 06:28 PM

It brightens it up, but does not do anything for the washed out issue, or the black normal artifacts. Any other ideas?

avatar image ZoltanE May 02 '16 at 06:49 PM

What I meant was adding the emissive color to your original material. In these recent ones subsurface color is not linked up at all.

avatar image worldlearner0411 May 02 '16 at 07:04 PM

Sorry I figured less stuff would make it easier since subsurface was not affecting the shadowed areas. It actually does seem to change the black areas to a green color, however its washed out. The level of detail from the lit area to the shaded area is totally different.

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avatar image ZoltanE May 02 '16 at 07:18 PM

Perhaps tone down the emissive a bit, low enough so it doesn't make the lit areas glow but high enough to remove pitch black pixels in the shadow. Try to find the middle ground between the two kind of ugly.

Or you could try to use the new light channels. I haven't tried this so I'm just speculating but if you could make a faint, shadowless distant light which only affects the grass then that would help too. That "grass filler" would provide subtle directional lighting even in the shadows of other lights.

avatar image worldlearner0411 May 02 '16 at 08:00 PM

Well here is the best so far. It def. looks better, but I really wish I could get more depth. It would be nice if I could adjust AO in only shaded areas.

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If you or anyone else has any other ideas that could be used to improve upon this I would love to hear them :)

best so far.jpg (3.7 MB)
avatar image ZoltanE May 08 '16 at 07:12 AM

If you found an answer helpful then please mark it as accepted. :)

avatar image worldlearner0411 May 08 '16 at 07:15 PM

Absolutely...although my problem was not entirely solved, it was partially solved.

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