iRays Dev Team answer about too dark indoor scenes

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  • gerster said:
    Mendoman said:

    I think Iray might still have same problems that Cycles used to have before Dynamic range ( Filmic ) was improved. Changing ISO etc. tone mapping values has a tendency to wash away details, so it's not always a solution. Those who are interested, this Andrew's post about it explains it much better than I can: https://www.blenderguru.com/tutorials/secret-ingredient-photorealism

    Thank you, that video was super helpfully to unerstand.

    So basically the issue is not the light bouncing of iRay, it's the color system!

    If we would have a better color system we would have no clipping and would need no ghost lights.

    Ghost lights (or other means of adding light to inaccessible areas) will help with render speed (convergence).

  • fastbike1fastbike1 Posts: 4,081
    edited January 2020

    You can do that with tonemapping. You need to know what the tools can do. It's not a trick.

    TheKD said:

    The big thing render engines are missing IMO is an eyeball mode. A mode that can mimic more what our eyes see instead of what a camera can see. Not everyone is looking to fake a photograph, I want it to seem more like you are looking on a scene with your eyeballs, rather than looking through a camera lense. Probably easier said than done lol. For now we gotta do tricks to get what we need.

     

    Post edited by fastbike1 on
  • PadonePadone Posts: 4,065
    edited January 2020
    Rafmer said:

    As it should be. You cant see evenly lit two environments with so different illumination. Not in a photo, not with your own eyes either.

    This is not entirely correct. It is true indeed that a real camera has to focus on the mid-level lights, so one part of the picture may be overexposed and one part underexposed, depending on how much difference there is between light conditions inside the camera frame.

    Human eyes on the contrary work in a different manner. The eyes are able to adapt very quickly to the part of the subject we are focusing at. In a sunny day we can look at the sky and we get it fine, we can also look at some shadowed corner around us and we get it fine as well, all within the same environment. Indeed if you were walking yourself on the street posted by @gerster you would not see a white sky at all. Did you ever see a white sky in your life ? That's because human eyes are just tools passing information to the brain. We don't see with the eyes but we see with the brain. This is technically called "perception". The brain also tends to remove color dominance, for example giving us the perception that in a yellow light inside an apartment the light is white and the white items are white. While if you look at the apartment windows from outside by night you will get the yellow light.

    To simulate human eyes with iray we have to turn off the burn highlights and crush black settings in the tonemapping panel. This will map the whole linear range of the picture to the srgb space making it visible in the output device. That is similar to what our eyes and brain do to get our perception of the environment.

    Post edited by Padone on
  • lilweeplilweep Posts: 2,779

    I read that even with turning off crush blacks/burn whites, the dynamic range is still quite low (8 bits).  But then I have read elsewhere that you can do tone mapping over full 32-bit range if you export as beauty canvas.  I would like to read more about tone mapping in post using photoshop but everything I read just assumes a detailed level of understanding already, of which i have none.

  • DustRiderDustRider Posts: 2,903
    gerster said:

    I talking about post editing tonemapping with affinity photo. It's just two clicks. I don't do tonemapping in DAZ.

    IMHO, you are missing a huge part of the capabilities of the render engine when you refuse to learn how to use the tools provided. Why render the image, and hope it will look like you want when you tone map it in post, when you can easily do it in DS. If you still want to tone map in post after getting it close th "right" in DS, you'll have "better" data to work with in post (a greater dynamic range of pixel values)??? You seem to believe the person that posted the query on the Nvidia Developer Forum, and not the responder. The problem isn't Iray, the problem is the person making the post clearly didn't understand what they were doing. Iray isn't an auto light sensing phone camera. It's a 3D render engine. The user has full control of the camera and scene lighting (though in many cases this isn't evident because DAZ and the PA's often do much of the work for the user). Therefor, the user needs to understand/learn at least the basics of lighting and camera settings if they plan to use anything other than pre-lit scenes and light sets.

    Additionally, IMHO, learning to effectively use the tools provided by Iray/DS will help you to better control the look/feel/quality your art in the long run, and also helps you to understand rendering better. Why guess at how the final image will look, when you can easily get close before using Affinity Photo. Lighting is key to the quality of the final image any 3D rendering process. That's why every major 3D animated movie uses dedicated lighting artists (actually every movie has people doing the lighting, not just 3D). Proper lighting is key to the mood and feel of any scene!!!

  • lilweep said:

    I read that even with turning off crush blacks/burn whites, the dynamic range is still quite low (8 bits).  But then I have read elsewhere that you can do tone mapping over full 32-bit range if you export as beauty canvas.  I would like to read more about tone mapping in post using photoshop but everything I read just assumes a detailed level of understanding already, of which i have none.

    If you want to do extensive post work then you shoudl render a Beauty Pass using Canvasses, in the Advanced tab of render Settings, which will give a high bit depth image (.exr). Iray works internally at high bit depths, but in DS the save is to an 8 bit per channel format.

  • Leonides02Leonides02 Posts: 1,379
    Mendoman said:

    I think Iray might still have same problems that Cycles used to have before Dynamic range ( Filmic ) was improved. Changing ISO etc. tone mapping values has a tendency to wash away details, so it's not always a solution. Those who are interested, this Andrew's post about it explains it much better than I can: https://www.blenderguru.com/tutorials/secret-ingredient-photorealism

    I get around this by bringing my Beauty canvas into Blender and applying the filmic preset.

  • PadonePadone Posts: 4,065
    lilweep said:

    I read that even with turning off crush blacks/burn whites, the dynamic range is still quite low (8 bits).

    The srgb space is 8 bits per channel. What the tone mapping does is not to extend the dynamic range, it is to map the linear space (hdr) to the srgb space (ldr) in different ways. An average output device can't display all the colors that the human eye can see. So these colors are mapped to a lower gamut in a way that the perception of them can be close enough to the real image.

  • lilweeplilweep Posts: 2,779
    lilweep said:

    I read that even with turning off crush blacks/burn whites, the dynamic range is still quite low (8 bits).  But then I have read elsewhere that you can do tone mapping over full 32-bit range if you export as beauty canvas.  I would like to read more about tone mapping in post using photoshop but everything I read just assumes a detailed level of understanding already, of which i have none.

    If you want to do extensive post work then you shoudl render a Beauty Pass using Canvasses, in the Advanced tab of render Settings, which will give a high bit depth image (.exr). Iray works internally at high bit depths, but in DS the save is to an 8 bit per channel format.

     

    Padone said:
    lilweep said:

    I read that even with turning off crush blacks/burn whites, the dynamic range is still quite low (8 bits).

    The srgb space is 8 bits per channel. What the tone mapping does is not to extend the dynamic range, it is to map the linear space (hdr) to the srgb space (ldr) in different ways. An average output device can't display all the colors that the human eye can see. So these colors are mapped to a lower gamut in a way that the perception of them can be close enough to the real image.

    Thank you for explanations.

  • gerster said:

    I did an other image to show the issue which I see.

    There are two G8Ms. One in the shadow and one in the sun. I think the skin of the one in the shadow is much too dark/grey.

    I'm do much photos with my smartphone, but I don't remmeber that there's such a big difference in the lightning in real life.

    Just take a look on these photo which I found on the internet:

    Just compare the girl in the front and the two people in the show on the right. There not such a big difference in their skin, compared to my render.

    not taking any sides here but just gonna say that the guy isn't even in the shade. proof: his shadow head isn't covered by another shadow.

  • gerster said:

    I did an other image to show the issue which I see.

    There are two G8Ms. One in the shadow and one in the sun. I think the skin of the one in the shadow is much too dark/grey.

    I'm do much photos with my smartphone, but I don't remmeber that there's such a big difference in the lightning in real life.

    Just take a look on these photo which I found on the internet:

    Just compare the girl in the front and the two people in the show on the right. There not such a big difference in their skin, compared to my render.

    not taking any sides here but just gonna say that the guy isn't even in the shade. proof: his shadow head isn't covered by another shadow.

    I assumed the cmprison was with the two right over against the wall - blurred with dstance but you can see the skin tone (though if so the tones don't match as well as the eye says - in the attachment I copied his face to a new layer and moved it over her face)

    Tone comparison.jpg
    266 x 137 - 7K
  • Matt_CastleMatt_Castle Posts: 3,066
    DustRider said:
    Why render the image, and hope it will look like you want when you tone map it in post, when you can easily do it in DS.

    Because you often can't easily do it in DS. Each test in DS needs to re-render to at least a reasonable level of quality to correctly preview the settings. For interior scenes, that could take a long time.

    If you're exporting as a 32 bpc EXR canvas, you have so much information and dynamic range that any post-processing is basically lossless (and much less time consuming than waiting to do it in DS), so it doesn't matter if you're starting from "better" values... but if you've applied bad tone mapping in DS, then you may have crushed or burnt the wrong tonal ranges to suit your final adjustments, and actually undoing that can be a problem.

    For similar reasons, I don't apply bloom in DS, but do it in post based on the areas that the EXR file tells me are overexposed. I can quickly test multiple different options without having to re-render from the start. The less post-processing I'm doing in DS (and it is still post-processing, even if it's being done from DS's options panel) and the more of it I have control over afterwards, the better.

  • TooncesToonces Posts: 919
    DustRider said:
    Why render the image, and hope it will look like you want when you tone map it in post, when you can easily do it in DS.

    Because you often can't easily do it in DS. Each test in DS needs to re-render to at least a reasonable level of quality to correctly preview the settings. For interior scenes, that could take a long time.

    Tone mapping appears in the hidden side pane of the Render window (as does Bloom). So when the render is done (or even during the render), you can expand this side-panel and play with tone mapping for 'free'. It doesn't cause a re-render. You may have to press the 'resume' button if the render is done, but it's pretty instant.

  • Matt_CastleMatt_Castle Posts: 3,066
    edited January 2020
    Toonces said:

    It doesn't cause a re-render.

    It certainly does cause a re-render on my system. (And I have just checked that in 4.12, in case I was remembering a problem from a previous version of DS/Iray that's since been fixed).

    Post edited by Matt_Castle on
  • It always looked to me that for interior renders light doesnt spread far enough, regardless weather the light is coming through the windows or interior is lit with interior lights or both. Result in darker parts of the image always looked unrealistically dark for the light applied.

    The "problem" was in the Burn Highlights - Crush Blacks render settings. At default values they are lightening lighter parts and darkening darker parts, thus making higher contrasted images. Now, I usually render with Burn Highlights 0.15, Crush Blacks 0.05 and Saturation 1.05 (to add up little color lost with lowering the contrast).

    So, for start set the Crush Blacks to 0 and see how light-dark looks then.    

  • Oso3DOso3D Posts: 15,095

    Changing tone settings while rendering cases re-render IF you have canvasses enabled, otherwise it does not.

    Yeah, that took a lot of 'wth' before I figured it out.

     

  • Matt_CastleMatt_Castle Posts: 3,066
    Oso3D said:

    Changing tone settings while rendering cases re-render IF you have canvasses enabled, otherwise it does not.

    I did suspect that as a possibility, and did test it both ways. It still seems to re-render in both cases.

  • outrider42outrider42 Posts: 3,679

    I'm not sure what you are talking about with needing to re-render after making tone map changes. I can alter the tone mapping/bloom/denoiser numerous times while rendering and the render does not restart. Since tone mapping is a post effect, it doesn't alter the status of the active render. 

    You might see the iteration count start over, but the actual render is still there, and the changes will kick in after a few iterations.

  • p0rtp0rt Posts: 217
    the problem is specular maps, with all shader packs using different levels, the only way to iray work well is to use luminance to tweak HDR's and make custom maps for shader using a setting that works well with your HDR level
  • OstadanOstadan Posts: 1,130

    I've never been able to figure out when tweaking the tone map will result in a re-render or a continuation.  I see both results, and haven't yet discerned a pattern.

  • QuasarQuasar Posts: 681

    There's another aspect to consider when lighting indoor scenes with outside light that's coming through windows. A regular glass shader that isn't set to thin walled won't let light pass through normally if the shader is applied to a flat plane (or even 2 flat planes that aren't a closed 3D object). So, if your windows are just a single plane, make sure the shader is set to thin walled.

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