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Ocean Lighting ... Help! Why does Spotlight render caustics and distant light doesn't?

DrowElfMorwenDrowElfMorwen Posts: 536
in The Commons

Main question is in the title. I have JM's undersea lights for Iray. I decided to take the 'Water Surface' prop used for making caustics, and duplicate it over my scene, thinking I could get caustics everywhere... and to do so evenly, I wanted to use a distant light, not a ton of 'Water Caustics Lights' that seem to just be spotlights. However, when I go to render with a distant light, NO caustics show... I don't get it. The physics should be the same, yes? There are no apparent special settings on this caustics light, so I don't understand why it's not working.

I have this problem all over: I can do caustics only on the small scale, and never on the big scale. I really want to change this. Please, any advice is welcome!

 

PS; yes caustics is enabled, so please don't ask.

Comments

  • agent unawaresagent unawares Posts: 3,513

    The product is unclear. Is this actually caustics or a selectively blocked light?

  • DrowElfMorwenDrowElfMorwen Posts: 536

    The caustics is created with a spotlight shining down on a plane which has a bump map applied to create the caustics effect. It works just fine on its own (sometimes... for some reason I cannot get them to render half the time!) but using any light other than the one included just messes it up, and it makes no sense. :/

  • agent unawaresagent unawares Posts: 3,513

    Okay, I think it has something to do with the distant light being too far for the caustics to work with the setup. I created two primitive planes, one above the other with water shader and fractal map displacement to make waves. A spotlight above it made very nice caustics on the bottom plane. A distant light with the same settings did not, only blotches. As I pulled the spotlight further away from the scene, it went from nice caustics to blotches like the distant light. Maybe rays are too straight at the distance, maybe there is a way to tweak the geometry of the scene to work with distant lights, I do not know.

  • DrowElfMorwenDrowElfMorwen Posts: 536

    Thank you, I have been testing this as well and could not figure it out. I guess this means big ocean scenes with caustics are out of the question! :(

  • agent unawaresagent unawares Posts: 3,513
    edited August 2017

    I found a good start point. Make two primitive planes and scale both to 1000%. Y-translate one up 100 units; this is the water plane. Apply the normal Iray water shader, then go into displacement and add this texture, with minimum displacement 0 and maximum 5. Make a distant light shining down through the water. You will get something like test render.

    I found that raising and lowering the plane as well as scaling the texture map and changing displacement all had major effects on whether the caustics got washed out or not. Once a sweet spot is found a tileable displacement texture would let you scale the water plane to cover the whole scene while tiling the texture at a smaller size to keep the right size of the displacement details. (Mine is not tileable, sorry. EDIT: I lied, it is.) Different displacement maps have different detail sizes so they'll all need different settings.

    waterdisp.jpg
    512 x 512 - 42K
    waterdisptest.png
    450 x 600 - 488K
    Post edited by agent unawares on
  • FishtalesFishtales Posts: 6,115

    Perhaps the brightness of the Distant Light is too low for the caustics to show up. When first loaded the lumens are set at 1500, adding a few zeros will bring up the intensity.

  • DrowElfMorwenDrowElfMorwen Posts: 536

    agent, I did what you suggested but I am not getting any results of caustics at all. I will keep playing with it, though.

  • agent unawaresagent unawares Posts: 3,513

    I set up a new scene to test and it has the same results. Make sure lighting is scene only so the environment light doesn't interfere and that your water plane has enough divisions for the geometry to support displacement. I have 300 on mine. I am running the latest stable version of DS in case there is a difference there.

    caustics.png
    450 x 600 - 400K
  • IvyIvy Posts: 7,165
    edited August 2017

    I think alot of water issues has to do with light angels and the water texture your using especially Iray and transparencey maps .  I don't have the set your talking about so I could not test it. But I have done similar effects  as you stating you wanted to make using  "The Philosophers Animated water  and I had successes in a push of HDRi light  through the water pane for under water scenes I did .   it worked great. I know it makes no sense. but some props never do what I want them to so I try other props to see if i have the same issues trying to resolve what is causing problem with my orginal prop. & why i can not accomplish what I am looking to do with a certain prop . its how i find solutions for some of my animated scenes.. Funny thing is water is the one that gives me the most trouble when trying to get caustics right  when working with iray

     here is a animation of what I am talking about pushing hdri light through a water pane.

    Post edited by Ivy on
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