STAR TREK 2d20
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  1. #21
    Just to inform the discussion a bit more, I tested how a couple of other programs handle lighting and overlap.

    The first one is Roll20, which as far as I could see doesn't have a colour control for lights? (It's been a year since I used Roll20 as a GM rather than a player so I may simply have missed it).

    They do seem to have a bit of the "lens" of light that's too bright in the overlap, but is is soft-edged and rather subtle - I'd have to try it on a flat grey background rather than my standard map example to be 100% sure it's the lighting not variations in brightness on the example map.

    The second one is Foundry.

    I would say they are doing a slightly worse job of the saturated red + saturated green = saturated yellow, but it is avoiding colour clipping on the bottom left.

    The desaturated lights, bottom middle, look to my eyes as though they are colour clipping right in the middle, but it's softer-edged and more graceful looking than the FG example in my opinion.

    Where they definitely are doing a better job is what I would think of as the most common use-case - two overlapping lights of the same colour, in this case a moderately-saturated yellow that I'd use for candlelight. There's no hint of colour clipping in the overlap there. I'm not sure how they have achieved it, but there's no question that the result there is significantly closer to physical reality than the FG results using default FG settings for the candles.

    I don't know if Foundry are doing this by better rendering model or some sneaky tweaking of default settings to avoid the issues, but I definitely think it's worth a second pass at the rendering model in FG to try to avoid the ugliest colour clipping problems.

    Cheers, Hywel

    Screenshot 2021-05-17 at 10.09.52.png
    Screenshot 2021-05-17 at 09.54.54.jpg
    Last edited by HywelPhillips; May 17th, 2021 at 12:24.

  2. #22
    Thanks for all the informations on lighting. I can't see your last 2 attachment though.
    Edit: it works now, thanks.
    Last edited by Egheal; May 17th, 2021 at 12:42.

  3. #23
    Don't know what happened there, have reattached the pics, seems to work now for me.

    Hywel

  4. #24
    Final post from me for the moment - just to show that it is possible to make nice lighting look good with FGU.

    Key tips:

    1) Avoid overlapping the bright light portion of lights - this will almost always lead to ugly colour clipping. That's especially true for lights of the same colour, and very very much true for lights with relatively pale pastel tints. They will blow out to white straight away. Fewer lights = safer. Don't put two candles next to each other even if they are like that on the base layer map. Use a single candle and increase the distances instead.

    2) As default, try using alpha of about 200 rather than 255 for everything. This gives you some headroom to avoid clipping.

    3) Falloff 99 for dim light is your friend. Gives a much more natural look, although admittedly does make it a lot harder to distinguish dim light from Fog of War colour. Nonetheless, if you want to avoid artefacts, it is well worth doing. Play with this if you need to distinguish dim light mechanically. For prettification, 99 is the way to go.

    4) Choose more saturated colours. The more pastel they are (ie the closer all components are to 255) the more likely they will clip to white before you want them to. So for the two torches I wound down the blue channel quite a bit to avoid losing the yellow when lights started to overlap. Ditto, the bonfire in the middle is quite a deep orange with not too much green and very little blue, and the ghost's glow is blue 255 and 0 in the other two channels and alpha down a bit to 200 ish. They can all overlap their dim lights without any nasty artefacts, and the bright light overlap is OK for everything except the two torches (see hint 1 above).

    5) For "pretty effect" lights rather than stuff you want to use to keep game system track of dim vs. bright light, use 99 falloff for both bright and dim light, and consider doing 1/3 bright to 2/3 dim instead of 50:50. Again gives you more headroom to avoid clipping whilst keeping a nice look for the central part of the light.

    When I move things around, they no longer clip in a really ugly way unless I overlap the bright light segments of the two torches.

    Screenshot 2021-05-17 at 12.55.51.jpg

  5. #25
    Not actually the last post from me it turned out, as I suddenly thought of a simple solution to the clipping highlights problems that camera manufacturers used extensively in the days of very limited sensor dynamic range:

    use a "knee".

    Here's a fairly simple explanation from Sony:

    https://helpguide.sony.net/di/pp/v1/...000909107.html

    The idea is that once the brightness passes a threshold (the knee point) you stop doing linear addition and start doing something more complicated to preserve the highlight colour information. Take a look at the two picture samples on that page from Sony - you can see the highlights clipping to white in a very ugly way in the top picture, especially in the pink ribbon on the top left. That's what is happening to our overlapping pastel-coloured lights in the bright light zone. See how the knee preserves the colour information in the highlights.

    Again with the caveat that I am no computer graphics programmer, I believe it is possible to implement a knee relatively simply as it has been done in real time on cameras with very simple digital signal processing.

    These days we use colour look-up tables (called LUTs) in camera to do the job, which is an alternative approach which also has limited computational overhead.

    https://nofilmschool.com/what-is-a-LUT

    https://en.wikipedia.org/wiki/3D_lookup_table

    As I said, this problem has been around since the early days of digital imaging and there are standard techniques to handle them which do a better job of handling highlights without clipping. I hope that maybe the FG team can take advantage of some of this work and find a relatively easy off-the-shelf way to improve things I note that graphics cards and Unity have built-in LUT support, although whether it is in any way useful for FG's implementation I'm not qualified to say.

    Cheers, Hywel
    Last edited by HywelPhillips; May 17th, 2021 at 13:39.

  6. #26
    LordEntrails's Avatar
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    Great info Hywel. Both from what's happening and what we can do now as users to get the results we want. Thanks

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  7. #27
    We need the implementation of the brightness knee ^^

    All this information made me certain that changing the additive nature of light from linear to logarithmic at a certain precise user-movable point is very important for multi-bright-colored-filled maps to avoid color cancellation to white mix.

    I have been playing with falloff and indeed, your recommendations are working, but I can see the limits of FG lights when having two small rooms with a door separating them and a colored light in each. The moment the door opens, we lose the color and the mood we wanted to set in each room.

  8. #28
    Quote Originally Posted by HywelPhillips View Post
    Final post from me for the moment - just to show that it is possible to make nice lighting look good with FGU.

    3) Falloff 99 for dim light is your friend. Gives a much more natural look, although admittedly does make it a lot harder to distinguish dim light from Fog of War colour. Nonetheless, if you want to avoid artefacts, it is well worth doing. Play with this if you need to distinguish dim light mechanically. For prettification, 99 is the way to go.
    I'm hoping there will be an option to turn off FoW which will make the falloff of 99 look great. An option in the Options panel for people like me that don't need FoW.

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