Strange effect white walls interior sequence output

[dvanderkeur]

Hi,

Started using unreal very recent i am still exploring and learning to use it for architecture visualization. I run into this effect i can't explain. Here's an example:



The walls show the effect, but it's also showing on the drawers on the right... This is a jpg created with the sequencer, highest resolution. It happens with and without a (seamless) texture of plaster applied. And changing the mesh (imported via datasmith) to unreal geometry makes no difference. I am using raytracing and a HDRi in combination with directional lighting. In the editor i have, in general, no problems and textures are rendered fine but sometimes things (like the wall in the picture) start 'flashing'. I think that flashing is related to the crappy output i get... But i have not a clue what setting i should tweak.

Could anyone point me in the right direction?

Since this is my first post, please let me know which information is missing or if i am not following certain forum guidelines. Thanks for any help in advance!

Danny

[presto423]

Post the directional light, skylight, and HDRi settings...but only the main (immediately under Mobility) and in the Lighting tab. Don't forget to include the Advanced settings for those. So, in the screenshot for each, the Mobility will be showing at the top, and try to fit as much as possible in one screenshot...if needed, simply take another screenshot to fit the rest of the settings. I know it's asking quite a bit to put all those up in the thread here, but it really doesn't take long and helps much better in others being able to help you. I see the noise on the walls, drawer, and ceiling. It likely has something to do with lighting and/or mesh settings for those meshes. There's a blurb about ray tracing and flat surfaces / materials in the doc pages somewhere, hinting that it can be due to a number of different things, one of which is the denoising isn't completely working, and another that the RT solver is unable to solve those types of areas. Changes need to get set in the project and often in lighting as a workaround or fix.

I have a question. With the HDRi, is there a skylight as its component? is there another skylight in the scene, in addition to the HDRi-included skylight?

What is the cubemap resolution of the HDRi?

[dvanderkeur]

OK, thanks for the reply. I will upload that info as soon as i am home again (likely Wednesday or Thursday). And it's no trouble of course. Very glad to get some help with this :-)

[dvanderkeur]

Uploaded the settings...

Directional light settings:


HDRi Backdrop:


HDRi backdrop detail (resolution):


Regarding the question about another skylight: no there is only the HDRi and the directional light in the scene. And some point lights. But i already tried with the point lights disabled and the same effect occurs... Not sure what you mean with 'skylight as its component' as it's component though.

I was wondering if it would be usefull to share world settings, post processing and mayne some project settings?
And hardware specs could be of use maybe?

Anyway, hope the uploaded info is helpfull but if i need to supply some more details just let me know. Thanks again!

Regards,
Danny

[presto423]

I noticed a few things in the settings posted. Here's a list:

1. Specular Scale is set at 0 in directional light. It might be affecting how the ray traced lighting, and other lights, are getting calculated and solved for those flat surfaces. AFAIK, UE4 is rather sensitive to changes or modifications to specular in lighting. It might not be the primary cause, but it's probably affecting things.
2. Samples per pixel in directional light is at 1, which is rather low, especially for the wide angle you're using in the directional (~3.2). It's interesting that it doesn't look somehow worse because for dynamic lighting and ray tracing, 1 sample per pixel is seemingly not enough.
3. In the texture editor settings for the imported HDR image, the Imported Size is gigantic compared to its display resolution and max-in-game resolution. It's having to be scaled down by about 12x to match those displayed resolutions. This is where I think that noise is coming from too. Since it is utilizing HDR, and not sRGB, there could be a problem with the rendering of those walls / large, flat surfaces...and even the drawer unit. I suggest you do a close reading of the real-time ray tracing pages, and review the HDRI backdrop page on the site. The imported resolution shouldn't be so large, I think, because it's going to be resized to a far smaller level. In other words, pixels are getting squeezed extremely tight into the final HDRI, which is partly where lighting is calculated from (similar to a skylight cubemap, as it's also a cubemap). Try re-sizing the original HDRI to around a 4K resolution (closer to a 3840 x 2160 size), and then re-import...after reviewing the HDRI backdrop page to ensure you're following the setup correctly according to it.
4. In the HDRI page, read about the ground plane that is required. If the ground plane is offset by a small amount, or not aligned correctly with the HDRI backdrop and meshes of the building(s) in the scene, it could result in light leaking from underneath the ground plane / HDRI. That'd most definitely cause artifacts / noise.
5. Lighting Distance Factor could probably use tweaking. Decreasing it a bit could help, or increasing a bit, but be careful not to modify it in conjunction with a bunch of other settings too before changing back because it's said on the HDRI page it causes artifacts if not used carefully. Since your scene is using RT, it might be interfering with the solving of those artifacts / noise on larger lit surfaces such as the walls / ceilings / etc. Other objects might look better too if it's decreased / increased to compensate for the differences in lighting between the HDRI and the lit areas (meshes comprising the building exterior and interior).
6. Last one, when re-sizing and / or re-importing the HDR image, try changing the compression settings (Lossy Compression Amount, and Compression Quality) to the least amount of compression possible without completely removing compression from the process. Dynamic lighting for such a scene is said to be cheaper than static or dynamic for other types of scenes (such as games with a hundreds or thousands of assets everywhere and with a ton of variance). So, I wouldn't worry about rendering speed or performance unless completely shutting off compression. And if you reduce the original HDR image's size from ~12,000 x 6,000 to 3840x2160 or somewhere around that, it's probably going to be faster than before, if it's even noticeable.

For now, try any / all of those suggestions. Then, based on the results, the other settings could be worth examining.

[presto423]

A few other things for the HDRI import settings:

a) Select "NoMipMaps" for Mip Gen Settings to use full quality
b) To answer your question about skylight, a skylight comes with the HDRI backdrop actor as a sub-component. I don't know if its settings are accessible via the details panel of the HDRI, but they may be accessible via a blueprint.

From the HDRI page, under Cubemap property, "Assign an imported HDR image that will be projected onto the ground and backdrop, and is used by the built-in Sky Light source." And more on it in the next property description for Intensity, "Sets the intensity of the embedded Sky Light and how emissive the backdrop HDR image is. Higher values result in brighter ambient lighting being samples from the HDR image (cd/m2)."

c) In the Import settings, set the Power of Two mode to a value other than None. It's like the cubemap resolution for skylight, so I'd remain within a reasonable range of 512 - 2048...perhaps 4096, but advise not using a higher value.

[dvanderkeur]

1. Changed specular back to the default value of 1. Nothing much happen indeed. I'll leave this at 1 in the future


2. Changed this to 4. Can't notice much difference though... At least not regarding the effect on the wall. Will keep this in mind though.

3. Yup... Very new to this all ;-) Scaled it down to 3840 x 1920 (aspect ratio is like that). Performance wise this does a lot. Thanks for that... :-) Will do some reading on this matter!

4. OK, i did nog have a ground plane so created one and put it on the same z level a the floor. Gave the floor thickness. Then moved all adjacent geometry up until all artifacts where gone. That was a hell of a job. Since i didn't make this (sketchup) model i'll probably spend more time on validating the imported geometry. This helped a lot! But still there is thie same strange effect on the walls...

5. OK, changed this back to the default since it's obviously better tweaking this after the overlall lighting is done.

6. OK, changed this to 'No lossy compression' and 'Lowest' for Compression Quality which is, i asume least compression.


a) Select "NoMipMaps" for Mip Gen Settings to use full quality

Done

b) Ah, now i understand. Yes there is a skylight in the HDRI component and i can adjust the intensity. I already saw that this has a big influence.

c) Could not find any Import setting called Power of Two mode. I did find a texture section in the HDRI cubmap details wher i can put the value 'Power of Two'. Is that what you mean?
This causes padding (probalby because of the aspect ration og my HDRI pcture... so put the value back to none...

Since the effect on the walls was not gone, i decided to start from scratch with all the things i learned in mind. Migrated my materials from the old project, start with the default HDRI and an directional light. Applied the textures to the imported datasmith geometry. And........ everything is fine.



Can't explain it. If i find out, i will post it.

[presto423]

Wow, I've seen a number of other scenes where starting a new project and migrating assets and materials over worked to correct noise / artifacts. And probably changing some settings to get better perf and results. I wonder whether doing things in a certain order influences the scene to become noisy like it was before on the walls, etc. I haven't found a guide or tutorial(s) on the correct order of scene lighting and setup to avoid it.

[S-Dot]

It was probably just one of the 1000 settings that exist that you changed while trying to fix things and then forgot that you ever changed it. Happened to all of us. Once you start a new project all settings will be more or less default. Be really really careful changing settings you don't really know what they will do. And if you do change them and see no effect change them back immediately. Otherwise its easy to end up with weird explainable things happening.

Not every setting in the editor that can be changed should be changed. In fact more of the settings probably should be left alone than the ones that are meant to be changed.