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Thread: HDRI Exposure Control ?

  1. #31
    Thanks again for your help and interest with this RPSchmidt.

    OK - Ive tried all of that and I get very different looking results with the two methods.

    I think the only way we are going to figure this out is to all be looking at the same scene. Ive simplified things down to make sure its not my texture images on the model causing issues. All Ive got now is a simple jet object model with a single surface set to conductor. Ive included a sized down verison of the HDRI in the scene to keep the download small, but it works perfectly for lighting and reflection.

    HDRI_spec_direct_test.zip

    Would you be able to open the scene on your side and see if you get the same results. One of these images is with Raytrace+Backdrop and the other is Raytrace Only. Single Environment light in the scene set to sample backdrop. As far as I can tell Im using the correct settings, but perhaps you can check that and see if you get the same render results.

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    I should have started this conversation by saying Im in Lightwave 2019.0.3 on Mac 64 - what version are you running?

    - - - Updated - - -

    Quote Originally Posted by Asticles View Post
    I'm sorry if I haven't helped you so much.
    Asticles! Thanks so much for everything, youve been a big help. Would you mind downloading the test scene Ive uploaded and seeing what results you get on your side?
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  2. #32
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    Thanks for the kind words.

    Have tested the scene and seems that isbg from background is not working properly, in my tests.

    Environment light version:

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    Backdrop version:

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    Disabling GI makes no difference, how strange.
    Last edited by Asticles; 09-13-2019 at 02:21 AM.
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  3. #33
    "Disabling GI makes no difference, how strange." - I also noticed that

    Did you notice a big change in the appearance of the Specular Indirect channel? That seems to be the main contributor to the different results.

    I gotta say though... this kind of seems correct to me. I would have been surprised if switching between "Raytraced+Backdrop" and "Raytrace Only" gave the same result. I always expected them to be different which is why the workaround in that video didnt quite add up in my mind. So is this a fault in the software, or is this how its supposed to work....

    Lets see what results others get.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  4. #34
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    And this is blender version, which is closer to the Lightwave's Environment light one.

    Click image for larger version. 

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    Blender environment is a bit brighter
    Last edited by Asticles; 09-13-2019 at 02:38 AM.
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  5. #35
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    Click image for larger version. 

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    Environment light + Raytrace+Backdrop seems incorrect to me (double lighting).
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  6. #36
    Quote Originally Posted by Asticles View Post
    Click image for larger version. 

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    Environment light + Raytrace+Backdrop seems incorrect to me (double lighting).
    That results looks very similar to the Blender result - just a lot brighter.

    Its weird though, none of your results seem to 100% match my Raytrace+Backdrop Environment Light version below, which looks the most correct to me.

    Click image for larger version. 

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    Last edited by scott.newman.ct; 09-13-2019 at 02:50 AM.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  7. #37
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    Use in your scene the srgb preset and you will see the light brighter.

    Edit: what seems clear is that Backdrop without an Env light is broken.
    The problem with blender version is that the environment is a bit brighter. Try to decrease the exposure in photoshop to match the LW background, if you want.
    Last edited by Asticles; 09-13-2019 at 02:52 AM.
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  8. #38
    Quote Originally Posted by Asticles View Post
    Use in your scene the srgb preset and you will see the light brighter.
    Why would you use the sRGB preset? Surely an HDRI should be set to 'default" or "linear"?
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  9. #39
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    Quote Originally Posted by scott.newman.ct View Post
    Why would you use the sRGB preset? Surely an HDRI should be set to 'default" or "linear"?
    You have set the light color and picked colors to sRGB, I was talking about that.
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  10. #40
    Quote Originally Posted by Asticles View Post
    You have set the light color and picked colors to sRGB, I was talking about that.
    umm... now Im completely lost. I dont know what you mean by that?

    Also, when you say "what seems clear is that Backdrop without an Env light is broken." - Im not sure I understand or agree with that point either.

    Perhaps somebody with some official Lightwave Support/Development team contacts could inform them of this discussion and shed some light (excuse the pun) on what the correct outcome is supposed to be here.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  11. #41
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    Quote Originally Posted by scott.newman.ct View Post
    umm... now Im completely lost. I dont know what you mean by that?
    This:

    Click image for larger version. 

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    Quote Originally Posted by scott.newman.ct View Post
    Also, when you say "what seems clear is that Backdrop without an Env light is broken." - Im not sure I understand or agree with that point either.
    Because ISBG sampling should lit the scene properly without lights.
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  12. #42
    Quote Originally Posted by Asticles View Post
    This:

    Click image for larger version. 

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    Because ISBG sampling should lit the scene properly without lights.
    Ah yes - I see. If I understand corrcetly, you are saying that even with no lights active in the scene, the object should render as if its directly sunlit (specular direct lit) from just the HDRI alone if GI and ISBG and sample Backgrop are enabled.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  13. #43
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    yes
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  14. #44
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    Good morning!

    Here are my results with various tests:

    Glossy Reflections ON

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    Raytrace Only

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    Raytrace+Backdrop

    Glossy Reflections OFF

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    Raytrace Only

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    Raytrace+Backdrop


    The next renders are with changes to the surface specular (65%) and roughness (35%) - Glossy Reflections OFF - Addition of a 4k HDRI - mipmaps on the HDRI environment texture are OFF

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    Topview Raytrace+Backdrop

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    Sideview Raytrace+Backdrop

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    Bottomview Raytrace+Backdrop

    Same views rendered with your original HDRI (which is a wee bit small for an HDRI at only 512px resolution) - mipmaps on the HDRI are OFF

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    Topview Raytrace+Backdrop

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    Sideview

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    Bottomview Raytrace+Backdrop

    Note on these last two series, I didn't do any Raytrace Only renders; I know that they will turn out exactly the same because Glossy Reflections are OFF.

    For my part, I like the consistency of the result with Glossy Reflections off. I can tweak the specular and roughness to get the surface result I am looking for. With glossy reflections on, I normally get more light blow out, and the overall lighting is too bright and not consistent with the scene.

    When I compare objects in full shadow in my HDRI with sides of my model in full shadow, when glossy reflections are on, there just always seems to be too much light and it makes me wonder where that light is coming from.

    Anyway, I hope this helps in some way. I didn't make any other changes to the scene, other than those noted.

  15. #45
    Thanks for taking the time to do the tests RPSchmidt.

    I notice your HDRI envirnoment got flipped somehow, so the render wont show quite the same results, but its still helpful to note the huge difference between "Raytrace+Backdrop" vs "Raytrace Only".

    For me, rendering with Glossy Reflections OFF is a realism killer for close up, hero objects. But it is very useful for getting rid of noise and bringing down anti aliasing times on smaller areas or simple objects that will stay further back from the camera.

    I was quite impressed with how well the despike filter actually worked in the end.

    Hopefully somebody from Newtek can get back to us at some point about what Asticles has pointed out about the ISBG sampling not working correctly.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

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