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Shadows not showing up correctly

I'm working on the lighting on an office scene And I'm seeing some issues in the shadows from some of the lights. I've gone through what I think it could be with no luck and was hoping someone else may have an idea or be able to point me in the right direction.

In the following picture there are two lamps, both blueprint lights and both completely identical, but only the one on the left is showing a shadow on the wall behind it correctly. The light is inside the bowl of the lamp so it makes sense that there would be a sharp shadow on the wall where the light gets cut off by the lamp. With the lamp on the right there is no shadow showing up on the wall behind it, however the shadow from that lamp is showing up correctly on the bookcase and computer monitor next to it.

This doesn't seem to be a lightmap issue, I've checked the lightmap on the wall mesh and all the UVs have their own, even sized space. I've rendered this image with a large resolution on the LM as well to see if that would help. They are stationary lights but there are only 3 of them in the scene and none have an X through them, so overlapping can't be the issue, and I have a Lightmass Importance Volume around the whole scene.

The wall is also one solid mesh, so I can't figure out why it would render an identical light 2 different ways. If anyone has any suggestions It would be greatly appreciated, I'd really like to understand as much about lighting as I can in here.

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asked May 22 '14 at 01:00 AM in Rendering

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Joe1029
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avatar image Joe1029 May 26 '14 at 05:27 PM

By the way, both pictures are lighting only.

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3 answers: sort voted first

Hi Joe1029 -

I have found out what is causing the problem, but no immediate solution as of yet. If you move your desk lamps to opposing corners of the desk the shadows will render correctly, this leads me to believe that there is an issue with the overlapping stationary light in the scene.

I will let you know if and when we find root cause or solution

Thank You

Eric Ketchum

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answered May 29 '14 at 03:24 PM

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Lovecraft_K ♦♦ STAFF
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avatar image Joe1029 May 29 '14 at 07:24 PM

Thanks for all your help Eric, I look forward to hearing about what your find.

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Try changing the lights to movable as a test - if the shadows now show up correctly then you know it is a lightmap issue, usually with the lightmap UVs on the receiving mesh. I know you mentioned you checked that your UVs are unique but that's all I can think of that it could be.

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answered May 22 '14 at 01:35 AM

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DanielW STAFF
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avatar image Joe1029 May 26 '14 at 04:04 PM

Hi,

Sorry about the late reply, I was out of town for a few days. I tried making the light movable and the result was the same. I went back and checked the lightmap again as well, and it is fine.

avatar image Lovecraft_K ♦♦ STAFF May 26 '14 at 04:21 PM

Hey Joe1029 -

Would it be possible to get a screenshot of this render from the same angle but mirrored behind the chair of the desk where the light works?

avatar image Joe1029 May 26 '14 at 04:36 PM

Hi Eric,

Thanks for the quick response. I believe this is what your asking for, let me know if its not. Lightmap resolution is pretty low on the wall (easier to tweak and rebuild), which is why the shadow is choppy on the left side. But even setting this to something really high doesn't help the right desk.

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avatar image Lovecraft_K ♦♦ STAFF May 26 '14 at 05:06 PM

Not a problem. And yes this is exactly what I wanted to see. I had a thought that it might have something to do with the material settings with the book case and how much reflected indirect light is coming off that one object which was causing the problem, but looking from this angle I do not see that as an issue.

Would you be willing to upload the *.uasset for the light blueprint so I can test a few scenarios here?

Let me know either way I will try to build something close and test it out,

Eric Ketchum

avatar image Joe1029 May 26 '14 at 05:14 PM

Yes I can send you the file. It's not my project alone though, so I would have to email it if that's alright.

avatar image Lovecraft_K ♦♦ STAFF May 27 '14 at 02:19 PM

Hey Joe1029 -

Check your forum messages.

avatar image Joe1029 May 27 '14 at 04:11 PM

I'm very sorry, but where are forum messages? I don't see a new message anywhere.

Thanks.

avatar image Lovecraft_K ♦♦ STAFF May 27 '14 at 04:17 PM

Hey Joe1029 -

Go here, **https://forums.unrealengine.com/**

and check your messages. It will be the same log in info as AnswerHub.

avatar image Lovecraft_K ♦♦ STAFF May 27 '14 at 06:59 PM

Hey Joel1029 -

I am still not able to reproduce what you have there, but I have a couple of ideas now. Try removing or moving the bookcase between your desks to see if rebuilding will fix the lighting. Also look at the metallic and roughness setting on your wall and desks. It looks like an assets reflective light is strong enough to override the hard edge shadow that's being produced.

Thank You

Eric Ketchum

avatar image Joe1029 May 27 '14 at 10:11 PM

Hi Eric,

So testing this out, removing just the bookcase and table and rebuilding light fixes the problem. Removing one or the other doesn't and using a different material on both doesn't do anything, even though the lamp on the other table is fine. Here is what it looks like with both removed.

I'd love to know what causes this or how you were able to determine what the problem was so I can avoid or fix this in the future. I can send you the level file if that would help.

The wood material btw was just 2 textures, dif and roughness with a black metallic channel. No normal, but I changed the mat on those 2 to a non-metallic with a normal and got the same result. Seems like the placement of the meshes. Doesn't make much sense to me though that removing just the bookcase doesn't fix it since the left side works with the desk.

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Hi Joe1029 -

I came about that suggestion knowing how light works in a real world setting and if you have enough indirect light it will fill in shadows created by a direct lighting source. What I was seeing in your pictures was the tight corner with a lot of indirect lighting coming from the desk and bookcase. So this seems this is the culprit to getting your direct shadow back.

You are saying that you tried different materials, but have you played around with roughness, specular and metallic settings in the bookcase and desk material to limit the objects reflective quality to a very diffuse settings (Roughness close to 1, Metallic at 0).

Ultimately though you will probably want to adjust the Desk Lamp PointLight's Indirect Lighting Intensity down to get less bounce contribution in the level. A setting of zero should render only the direct lighting itself and create the hard shadow. Perhaps start there and slowly raise the value until you achieve the exact look you are trying to achieve.

Let me know how it turns out -

Eric Ketchum

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answered May 28 '14 at 02:05 PM

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Lovecraft_K ♦♦ STAFF
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avatar image Joe1029 May 28 '14 at 04:46 PM

Hi Eric,

I'm trying what you suggested. Tweaking the roughness doesn't seem to have an effect on the wall, and setting indirect lighting intensity down just makes the wall black. Seems like its just not receiving any light at all from this source. In this pic I have indirect lighting set to 0 and you can see the wall takes no light from the light source at all, even though the outlet and power strip do. I removed the desk to see better.

This made me think of the lightmap again, so I checked again but it seems fine and checking the message log there's nothing about the LM on the wall.

The left light is still rendering correctly and removing the bookcase still makes this one appear correctly. Maybe there's something I just don't understand about lighting, but it seems to me that back wall should be picking up some light no matter the bookcases material properties.

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avatar image Lovecraft_K ♦♦ STAFF May 28 '14 at 05:08 PM

Hey Joe1029 -

At this point I will need to look at your project directly, can you connect with me via the forums.

avatar image Joe1029 May 28 '14 at 05:46 PM

I just messaged you on the forum.

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