Superfly - too much HDRI noise?


  • Poser Ambassadors

    I have done many experiments with Superfly noise reduction though lighting in Poser 11, like classfying SF noise in 2 categories:

    • Not enough light - can create noise like it happens with digital cameras in low light.
    • Too much light - can cause firefly hotspots. The sum of light rays per pixel exceeds the maximum value and becomes white.

    SF suffers from the lack of noise removal, like the newer versions of Cycles now have, and some other rendering engines already had for a while, like Octane and I-ray. So I must optimize the lighting to produce the least amount of noise possible.

    When I start rendering, I more or less know that if the noise doesn't dramatically clear in the first 30% of the remder, chances are it won't clear at all, no matter for how long I let it run.

    The major source for SF noise seems to come from emissive surfaces. Whenever I add an area light or HDRI lighting, noise dramatically pops up all over. Conversely, noise drops dramatically when I replace area lights with Poser spotlights. However, there are cases where I want HDRI because it fits the kind of scene and lighting for certain scenes.

    For some reason, the results seem to be quite inconsistent between one scene and another, even when I use the same HDRI and settings. Sometimes I get no noise, sometimes I get plenty. When it comes to materials, I have tried replacing PoserSurface with PhysicalSurface, or reducing specular to zero, or roughness to max while trying to identify major noise causes, but those things seem to have no effect on SF noise. SSS and caustics cause massive noise, though, that's a given.

    So back to lighting, sometimes it helps to add a faint spotlight straight from the camera to help reducing noise from HDRI lighting. This seems to be effective, even if faint - just enought to throw some light over the darker areas the camera can see, and therefore will render. Shadows are notorious noise sources when there isn't enough light.

    However, for areas well lit (not in the shadows), that's the part where I have the most trouble reducing noise when rendering with HDRI lighting. This is a case where noise spreads out evenly all over the place, apparently because HDRI comes from a large emissive surface around the entire scene (EZDome). In this particular case, sometimes I get massive noise, sometimes very little while using the SAME HDRI lighting. It seems inconsistent, or... more likely, I am not understanding the cause here. It's not fireflies for excessive lighting, nor lack of light on the shadows. It's just massive, generalized noise all over the scene when I use HDRI domes that won't clear even if I render overnight.

    SF has settings for noise-reduction like "Filter Glossy", "Clamp direct samples", and "Clamp indirect samples". I think those are more about avoiding firefly hotspots, though, which is not the kind of noise I have trouble with.

    Any suggestions?



  • @Ken1171 no suggestions but this is what I have found out from my render observations.

    1. High Fstop HDRI's make more noise and require more samples to clear up that noise.
    2. surfaces that reflect diffuse light make the scene more noisy. This can be demonstrated by using a closed room prop and lighting it up with an inf light coming in a window.
    3. Those fireflies you see when unclamping the render are actually highlights from the HDRI. If you let it render long enough you'll see highlights and shadows emerge from the fireflies. I have found that the high fstop HDRI's that are from outdoor scenes and show the sun are too noisy to resolve even with 100 samples. The hot-spot in the image (the sun) is just too small to resolve the highlights. High fstop interior images usually resolve with 70-100 samples because the hot spot will be a window that is larger in the image than the sun would appear. You want a quick render? Use a small JPG instead of an HDRI. I can usually get away with 40-50 samples on those.

  • Poser Ambassadors

    Thanks, I will try your suggestions!

    The HDRI I am using at the moment is the default outdoor one from DS. One thing I have noticed is that those images look huge, completely out of proportions when loaded into Poser. I suspect it could be because of the tiny world scale used in Poser? Sometimes I try to compensate with wide angle lenses, but that also introduces a lot of perspective distortion. Maybe it would be more of matter of scaling down the dome? That should also increase the emissive light since the emitting surface becomes closer, so it probably needs to be compensated.



  • @ken1171 cool! Here is an example of those fireflies. Fairly high fstop HDRI. Both have the dome set with a Poser root and ambient set to 3 to light the shadows in the scene to my satisfaction.
    0_1560803520245_firefly highlights.jpg



  • @ken1171 the other thing is that imo Huge HDRI's are a waste because I'm just going to use FOV blur and wont need all that detail from the background. 2k res is about as far as I go with the skydome hdri's. You also have to manage how much texture memory you are using if you are running GPU renders. If I go over a certain amount I get a render crash or a serious render slow-down.



  • @Ken1171
    I am aware of two ways of using an HDRI in Superfly

    Background Material
    I have found adding an HDRI file as an Environment Map to the Background material always produces noisy images. Even after 8 hours of rendering, the grainy noise was still too much.

    Dome Emission Object
    Adding an HDRI file as an Emission to the material of a dome object like EZ-Dome will produce an image without noise, but the shadows from the HDRI file is lost.

    I also confirm that some mesh based lights are always grainy, but others are not. I have some streetlights props that always make a grainy light, but the square prop does not.

    The only way I found to get rid of the noise is to use an AI Denoiser.
    The example I posted in the AI Denoiser thread (https://forum.smithmicro.com/post/64316) was rendered with an HDRI file on the Background material.



  • @willdial I only use baggensbill's envirosphere. You can get highlights and shadows with only a dome and and HDRI as I have pointed out in my previous post. It matters on the dynamic range of the HDRI file and if you turn of clamping or not in your render settings. The smaller the hot spot to more noise you will have and that goes the same for mesh lights. If you use small mesh lights that are kicking out tons of light you will have noise but larger mesh lights will be fine. Here is another image using only the envirosphere and an HDRI with high fstop value. Notice the highlights on her left and shadows on her right?
    0_1560822100164_Briallen sunny window.jpg



  • @willdial here is an image that only uses mesh lights from the model. neither of these images took more than 2 hours to render on a couple of old GTX cards.
    0_1560822205467_Car Expo.jpg



  • @ghostship "mesh lights" by which you mean the "actual" lights (ie: light emitting surfaces) in the scene?
    very nice!



  • @ghostship tool from the demi-god of materials. Check. I remember the ES producing excellent results, even back in the dark ages (err... not completely dark, obviously). I so need to bone up on my render skillz. And scene composition, camera work, textures... Sighs... At least i'm not bored :)
    btw, which hair and texture? It's producing nice shadows.



  • @thoennes yeah, mesh lights.. just using the bits of the model itself that are supposed to be lights in this case all those crazy tube shaped things and the circular ceiling lights. The car expo model is by Apple Jack at Rendo.

    the hair is Alanis by Fabiana (my textures and shaders) and the skin texture is a modified version of Vanessa by Maelwenn (daz)



  • @ghostship
    I probably not using terms properly so I will use an example of what I'm seeing.

    I used the Sunny Vodelpark HDRI from HDRI Haven: https://hdrihaven.com/hdri/?c=outdoor&h=sunny_vondelpark

    Here is the HDRI in Superfly with Envirosphere.
    0_1560830695411_HDRI Superfly.jpg
    Here is the same HDRI in Superfly with the Background material
    0_1560830712485_HDRI Background.jpg
    The rendering settings are the same.
    0_1560830741593_Settings.jpg
    I don't know what is causing the difference.



  • @willdial Is that a spherical HDRI? How are you mapping it to the background?



  • @ghostship It is a spherical HDRI and I am applying it to the Background material. I used VinceBagna's background material.

    Here is the same scene in Octane Render.
    0_1560831466073_HDRI Octane.jpg



  • @willdial I'm unable to map a spherical hdri to my background in the mat tab. It just puts the image on a square behind the figure. Can you do a screen shot of you mat settings for background. I'm also wondering if we are talking about two different things called background?



  • @willdial this is what I get when I plug an hdri into the background material.
    0_1560832322398_background.jpg



  • @ghostship I used one of VinceBagna's materials. I may not be able post up screenshot of it. VinceBagna added some other items, but the basic approach is to use the "Envrionment Map" node from the Cycles menu.



  • @willdial yeah, don't do that. lol


  • Poser Ambassadors

    There seems to be a lot of mystery around the effective way of using HDRI in SF. For example, it's very simple to do that in Octane and I-ray. It just works, and we don't have to load spheres/domes for that. Both these rendering engines have HDRI domes built-in, so we just plug the images in.

    In Poser SF I have 2 problems: too much noise with emissive surfaces (mesh lights), and a scale issue with HDRI images - they look huge in Poser scale. When I use them in Octane, the size looks "normal".

    Perhaps a consequence of the scaling differences is that the dome has a completely different effect in SF and in Octane or I-ray. It's like when using a flashlight inside your room, or inside a football stadium - completely different results. Since different domes have different sizes, I have a hard time trying to match scales in Poser. Why does it have to be so hard?

    So, is there a relationship between HDRI noise and camera fstop? Would you like to elaborate?



  • The problems with HDRi come from the fact that SuperFly does not have an environment light like Lightwave, I-Ray, etc have. We have to use an emissive light (bg shader or sky dome) which in general do produce more noice and increases render times. There is no way around besides reducing the dynamic of the HDR image. The differences in noice production between background shader and sky dome come from the fact that the bg-shder does not use importance samples while the sky-dome does. Unfortunately SuperFly does not give us access to the importance sample option.
    In the past i tried to use an upscaled point light (scene inside the point light) but that does not work you get super strange shadows.