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Thread: Light Types Selective to Volumetrics it seems

  1. #1
    Curmudgeon in Training Ma3rk's Avatar
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    Light Types Selective to Volumetrics it seems

    For me at least, here's another head shaking "Wow".

    Why aren't lights "uniform" with respect to certain attributes, PARTICULARLY when they're given parameter settings for things like Volumetric? I mean, shouldn't they be?

    If they can't use or do something, why would that be in their UI?

    This has been driving me nuts. Ok, granted, just a short putt around the corner, but bothering me for some time just the same as I keep coming running into this sort of thing.

    Case in point this evening is that apparently not all light types will give you volumetric "God" rays when you'd think they would.

    Since I got back to my main system (& luckily out of LA), I've been revisiting some things that I started nearly 2 years earlier. I got some nice looking stained glass windows working with Dielectric and the color would cast upon the geom in the scene & wanted to take things the next step with the lighting, & just couldn't get it to work. Other lights in the scene behaved as expected with volumetrics though. Was it the geometry? The texture? Evil Spirits?

    Nope. I finally hit upon what the problem was, & of course discovered a new one. I liked the look of the HDR used in the enviro light but couldn't get volumetrics through my stained glass windows to work with it. Pissed away a couple days trying to get that sorted & finally isolated it as the culprit.

    A simple spot light though works easily & looks great.

    But, how do you align it to work with the HDR? I'm using OD Tools HDR Presets btw to load in the HDR with an enviro light.

    Ya know, the now poo-pooed sIBL utility had a slick feature where, during the process of adding an HDR image, you could click on the sun center & generate the long, lat. info which back in Layout you could then set a light to use. Worked great. No longer have that function, at least directly. (Now if that bat rastard Oliver H. hadn't traitorously jumped ship to Houdini ...)

    Anyway for now, I just brute force eye-balled it, but wondering if anyone else has dealt with this sort of issue of aligning one light type to the sun from an HDR?

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  2. #2
    RETROGRADER prometheus's Avatar
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    you could use physical sky background on top or behind the environment...im in bed and not in front of the computer..but i could use that and you will get a sundisc in vpr..and also seeing it over the hdr backgroun..but it needs the right order setup when adding it.
    but it will be easy to manually match once that is done.


    hang in for a couple of hours..i need 1 more to sleep.

  3. #3
    RETROGRADER prometheus's Avatar
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    Good morning, coffe has been induced so...

    See image,
    I was a bit wrong in my description earlier..I think, though it may work..what I did in this image is to use both sunsky environment from dpont first, then add textured environment above that, this is not making the sunsky visible sits the textured environment overrides that visibility in vpr, but the sunsky allows for the sunsky sunmotion to recognize the sunlight (in this case the sunlight isnīt dpontīs light..but the actual lw native physical sunlight) but you have to select that light in the sunsky panel.
    Then for this physical lights motion properties you add sunsky sunmotion, this will allow for the lensflare to follow where the sunlight is, and as such you will see the flare and the sun direction in VPR directly, so itīs easy to rotate heading or pitch to match the bright sun in any hdr..in this case I did an offset of the lensflare so you can see it better, the hdr sun is a bit more to the left here.

    If itīs unclear or if you have any questions? just ask..I am awake and may be able to help for a while.
    And by the way, I think the lw team must have done something with the sunlight and corrected how the shadow size produces shoft shadows, I think in 2019.1 it was still a problem with it not yielding soft shadows if you increase light size, but now it seem to work.




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  4. #4
    RETROGRADER prometheus's Avatar
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    Another trick.

    If you go in to the texture environments rotation channel, you could add a channel follower..and point that to the heading rotation channel of your light, but to Note..you need to set the scale of that to a negative value, so -100 as can be seen in my screenshot.

    So when that is done, you can rotate your light in heading direction (never pitch with textured environments) and the texture environment will follow that heading direction, so the sunspot in the image will match the scenes direct physical light when you rotate that physical sunlight.








    And No lensflare... just to show the real hdr sun...







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  5. #5
    RETROGRADER prometheus's Avatar
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    To note and be aware of regarding the channel follower and background matching the heading when rotating the light, this will only work to a certain limit when rotating the light..and mostly within camera range so to speak, if you try a full 360 rotation and above that, it will not follow properly..it would need to accound for the background width wrap etc, so itīs just a hack that works for a certain heading range within the camera view.

  6. #6
    Curmudgeon in Training Ma3rk's Avatar
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    I'll give the SunMotion modifier a look. Not sure if that will work with the light types in 2019.1.5 that actually respond to volumetric settings. I haven't been able to use any of Denis DP lights for example. Standard Distant or Enviro don't respond which leaves just Spot and IES lights.
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  7. #7
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by Ma3rk View Post
    I'll give the SunMotion modifier a look. Not sure if that will work with the light types in 2019.1.5 that actually respond to volumetric settings. I haven't been able to use any of Denis DP lights for example. Standard Distant or Enviro don't respond which leaves just Spot and IES lights.

    it works with the physical sunlight..that is lightwaves 2019.1.5 native sun hosek wilkie.
    Forget about dp lights for this anyway..you do not need it.

    For volumetrics, distant and enviro and physical lights reacts to volumetrics, but I advice not to use global scattering in landscape scenes..why, it is too darn slow, only one control for light volume samples for quality and it takes forever to refine at a decent level, so I use my own primitive item, as fog and godray objects..now I have also gotten good enough results with fading the fog volumetrics based on distance to ground with nodal scalar layers, and I also use it without non pyroclastic modes.

    Unlike the global scattering system..which is soo limited and is slow to refine, and also is very hard to get anything else than very bright volumetrics..with standard primitive volumes, it is almost unlimited.
    I say that because I can control scattering scale, density, absorbtion with more control and absorbtion isnīt available in global scattering either, I can also give it a slight shadow density.

    So my advice is, stay away from the global scattering and learn to use other fog items...they need to revisit the Global scattering system.

    Image sample..using just my own fog items, the tree was a very very dense 3Ds pinetree..so every sprout wire is a polygon, instanced it a couple of times, so total scene poly of 1.7 millions and above.
    Some light leakage and artifacts I need to check up on.
    An HDR image in the background, which I in fact should replace with something else or just use physical sky.

    By using blue color on absorbtion here, I get a nice reddish dark fade off in the fog volumetrics which I like, I would have a hard time to get that right with Global scattering, and not have the image been blown out either with intense light.






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  8. #8
    Curmudgeon in Training Ma3rk's Avatar
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    That's not what I'm getting though. Take a look:

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    With a distant or any sort of Enviro light, no rays. Do I need to set up a specific null item for those to react with? I don't recall now; played with this well over a year ago mostly recalled it being a bit fiddly.

    With a Spot, I get the hard image & haven't found anyway to soften that w/ just the one light. Similar but opposite problem with the IES, no way to sharpen it. Wish I could find something between but going to do a render using the IES later today.


    For thes tests, I'm just using the volu settings for the lights for now leaving the fog & scatter settings alone. Is that what your referring to as the Global Scattering in the Volumetrics Render Panel?

    Also, you've only the single light source. How well does this play with other light sources? My library scene has 80 lights of various types for chandlers, sconces, lamps.

    If you like, I can take out the one HDR & package my test scene so you've an empty stage w/ some windows to play with. Crunches down pretty well then.
    Last edited by Ma3rk; 04-06-2020 at 01:00 PM.
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  9. #9
    RETROGRADER prometheus's Avatar
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    You need to adress volumetric distance for some lights, distance light should work, but itīs tricky..if you set volumetric distance to low or too far, the effect will not work.
    When I use my fog setups, I do not have to wrestle that volumetric distant.

    As for environment light, that I do not think has ever been intended and should not work for casting rays (not entirely sure) it affects volumetrics anyway, but since itīs environmental, itīs not a direct sharp light and as such it will not yield any shadow rays to speak of really..I think.

    Distant lights works with global scattering though...wait for render.

    I will check how my fog items works in a room.

  10. #10
    RETROGRADER prometheus's Avatar
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    so here is a standard distant light, make sure you drag your volumetric distance slider from 0 and move up till you see the beems showing, and donīt go to far with the volumetric distance.
    No time to refine the grain, noise an speckles for this little test.

    Affect volumetrics helps illuminate the rooms all global scattering overall.



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  11. #11
    Curmudgeon in Training Ma3rk's Avatar
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    Nope, they're just not having it.

    Here's the IES settings
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    And for the Distant light:

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    Even with 10X those values, not a glimmer of a ray.

    Here 's what's in the Volu Tab:

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    Should be obvious that something isn't working correctly. I'm going to take a look at this on the Win7 system as well as the laptop. Different systems & video cards. See what scares out of the shrubbery.
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  12. #12
    Curmudgeon in Training Ma3rk's Avatar
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    Took the sample scene to two other systems & having the same results. So, I'm going to post it here as a start to track this down. Primary question: Why am I not getting volumetrics from the Distant Light?

    IESvsDistLight.zip
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  13. #13
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by Ma3rk View Post
    Took the sample scene to two other systems & having the same results. So, I'm going to post it here as a start to track this down. Primary question: Why am I not getting volumetrics from the Distant Light?

    IESvsDistLight.zip
    Had you followed my advice given previously, you would have solved it earlier.
    just changed the volumetric distance..1m is Way to short...that is just one footstep away and the room is larger than that and so is the distance to the windows and lights.

    See image...



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  14. #14
    Super Member kolby's Avatar
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    In short, the volumetric distance is the distance from the camera from which the volumetric effect begins to be calculated.
    System info: CPU: Ryzen 9 3950X RAM: 32GB DDR4/3200MHz MB: Asus Prime X570-P GFX: Asus GTX 750 Ti / 2GB OS: Win10, LW2019x64

  15. #15
    Curmudgeon in Training Ma3rk's Avatar
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    [QUOTE=prometheus;1590327]Had you followed my advice given previously, you would have solved it earlier.
    just changed the volumetric distance..1m is Way to short...that is just one footstep away and the room is larger than that and so is the distance to the windows and lights.

    See image...

    I fiddled with that w/ no apparent change.

    Appreciate the help in any case.
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