IBL (image based lighting)

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  • Hi :)


    A thing i've been wondering about for some time is the implementation if IBL in Enscape. I often use HDRI's as skybox to achieve quick mood changes in lighting, but sometimes it behaves differently than expected.

    At the moment we can load an HDRI in the "skybox" option, but to what degree does it actually behave like IBL in other renderes? It seems like the "sun" is still used for lighting and shadowing, but the color cast is from the skybox?

    Can you elaborate on the behavior? and do you plan on supporting IBL in a more "traditional" way in the future?


    ... It seems like this is gonna be a new feature in Lumion 9, and that's why it peaked my interest again ;)

    https://www.youtube.com/watch?v=0PrpJ5hgrxM


    Best regard :)

  • Is the Enscape option "use brightest point as sun direction" not something like IBL? Could it be that only "use brightest color as sun color" is missing?

    This option seems to put the "enscape sun" on top of the skybox, and not use the actual lighting from the HDRI :) for examble i can take an overcast hdri and still have sharp shadows due to the use of the standard sun.

  • I suppose so the Enscape sun is placed at the brightest point of your overcast sky. But the HDRI should be still active.


    The skybox with sun seems to act like sIBL, only the sun color doesn't base on the HDRI. I suppose so here Enscape could be easy enhanced. Demian Gutberlet Could you set it on the wish list please?


    I'm not sure what you are missing. For me IBL is a wide field, it can be a basic HDRI environment. Is the skybox not IBL, if you turn down the sun intensity? Or are you missing importance sampling of the HDRI? Here I found a description of importance sampling. Maybe Vray and other engines are using the same technology. Could be great for Enscape too.

  • I just did some controlled tests to investigate the behavior, and the results are mixed :) I used the excact same scene and hdri, and tested in both enscape and Maxwell render.



    in the very controlled "balls" test, the pictures seems to get pretty similar if i enable the enscape sun at a low intensity:


    Maxwell:



    enscape, sun on (low intensity):



    enscape, sun off:



    - It looks like the "sun on" gets very accurate compared to maxwell.


    but in the next scene, containing a tree and grass, the results are very different. Here is the benchmark from maxwell:


    Maxwell:



    Enscape, sun on (low intensity):



    enscape, sun off:



    How exactly the systems work, i dont know, but for more complex scenes it seems to be hard to get an accurate result :)


    I can only imagine that it would be hard to use "studio-hdri's" with multiple light sources, to light scenes, but fortunately this is not a use case i often encounter :)

  • (Have the leaves been tagged with the "Vegetation" keyword?)

    I disabled it, so the material setups for maxwell and enscape are the same... just basic roughness settings :)

    i did do a render with the "foliage" setting enabled, but the results were more or less the same :)

  • Interesting tests. I think importance sampling would be useful for Studio HDRI with more than one bright spot. For the HDRI skies the current implementation works quite well, only the sun color could be taken from the HDRI.


    On my personal list to request is a softer sun shadow. I like light smooth sun shadows and I don't like to perfect sharp sun shadow of Enscape. What are you and the others thinking?


    Last I had the impression that Enscape is using a color mapping with internal burn control. At your comparison images it can be seen at the reflected sky sun area. It's nice to see how good Enscape handle this high intensities.

  • Your tests confirm my understanding of how Enscape's lighting setup works. It is using HDR for the fill lighting, but not allowing the key lighting to produce hard shadows. Basically the same thing as reducing the resolution and possibly the dynamic range as well for the purpose of lighting, and keeping the resolution for the visible background.


    However the fact that Enscape is not using full HDR IBL is not necessarily a bad thing... when rendering with HDR IBL, if the HDR contains a sun providing hard key light you end up with 2 sets of "hard" shadows unless you disable the sun. Even with automated matching of the sun angle (which is genius btw) one would likely not be able to match *exactly* hard shadows from both the HDR and the sun. So the method being used is a good solution for general use, flexibility of sun lighting studies, etc


    I would certainly welcome the option of using full HDR IBL allowing that HDR to provide the key light.


    This may not even be needed if we were provided a bit more control over the shadow softness from the sun. Even with Vray I typically would use a method similar to what Enscape is doing for flexibility. What I miss from that setup is the ability to control the sun size which allows us to create softer sunlight shadows.


    Chris

  • However the fact that Enscape is not using full HDR IBL is not necessarily a bad thin

    Almost! We just clamp away *VERY* bright pixels that would equal a sun within the HDRI. Everything else is handled as accurate as possible.


    On my personal list to request is a softer sun shadow.

    I think we'll add that for 2.5!