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Sunlight and HDRI Environment Maps

NaramatabenchNaramatabench Posts: 10
in New Users

This is a continuation from a previous thread that has dropped off the pages so I hope this is acceptable to the Moderators.  I have spent some useful lockdown hours playing with these HDRI maps and lighting. I came across "Tropical Beach" in HDRLabs. It looks very similar to "Spiaggia" - an excellent beach with full sun in HDRIHaven. Yet "Spiaggia" casts excellent shadows and the characters can move around in the sunlight or shade depending on Dome Rotation. "Tropical Beach" also has a full sun but the characters are always in shadow. I fully understand the point about such maps where there is no visible sun -  although there is lots of dappled sunlight amongst the trees as in Topanga Forest there is no "Sun" in the photo so no sun-lighting effect on the characters and no shadows. But this is not the case with "Tropical Beach". Can some expert please explain the difference in these two beach maps?

On a further point I tried placing spotlights in the scene to create a fake sunlight and shadow effect - good opportunity to learn about lighting. Except that I could not get them to give any light.  "Dome and Scene", "Infinite" and "Draw Dome" on. Obviously another beginner's error but what am I doing wrong? Finally, I tried "cut & paste" the Sun from Spiaggia into a Map with no visible Sun using PS as suggested by one of the experts but obtained nothing but a large black occlusion. 

Once again, very many thanks in advance for your assistance (and patience!).

Comments

  • margravemargrave Posts: 1,822

    What are your spotlight's settings?

    If you want to mimic sunlight, I'd recommend a rectangle about 150cm by 150cm, 5600K temperature, and lumens about 1,000,000-ish to start with. Probably more like 10,000,000, but start low and turn it up until before it gets blown out.

  • FishtalesFishtales Posts: 6,119

    To represent the Sun use a Distant Light set to a Temperature between 4500 and 6500 depending on the colour you want and Lumens between 10,000 and 50,000, sometimes one works better than the other.

  • NaramatabenchNaramatabench Posts: 10

    Thank you.

    The problem is I am getting no light at all - as if the Spot is not even there even though it is. And this is only a "fix" because I cannot get the "real" Sun to function in "Tropical Beach".

  • AnimAnim Posts: 241

    Tropical beach has the sun more or less shining top down. You get a shadow under the object. But that HDRI is quite weak regarding EVs - meaning even though there is a sun it is not very bright compared to the rest of the image. The total EV in that HDRI is 11. That does not mimic real life. The contrast between light and shadow is to weak to simulate a real sun / shadow situation. The "sun HDRIs" from hdrihaven have a much wider EV range. They note this for each image. Ofter you find 24 EV or even more.

    To emphasize the shadow go to:

    Render settings -> Environment -> Ground Shadow Intensity (works only for the virtual dome floor (Draw Ground = on) not for real geometry)

    Regarding the light: You need "Dome and Scene". If tone mapping is at exposure value 13 a distant light with Luminous Flux = 8000 should have an effect (if combined with Ground Shadow Intensity it might be to strong).

    Tropical-Beach_1.jpg
    914 x 599 - 75K
    Tropical-Beach_2.jpg
    734 x 577 - 50K
    Tropical-Beach_3.jpg
    999 x 708 - 81K
  • NaramatabenchNaramatabench Posts: 10

    Ah ha. That explains it - many thanks Anim for that. So it is not just the "Sun"; it is to do with dynamic range as well - the more the better.I'll stick with the HDRIhaven one.

  • AnimAnim Posts: 241

    Naramatabench said:

    ... it is to do with dynamic range as well - the more the better ...

    Well, I would say yes and no. There are cases where harsh contrasts can cause render issues. So, it depends on the individual scene.

    https://www.daz3d.com/forums/discussion/477651/blocky-shadows-from-hdri/p1

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