Refractive Caustics (Pool Water) - Weird Cutoff?

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Refractive Caustics (Pool Water) - Weird Cutoff?

Postby saberopus » Wed May 10, 2017 4:33 pm

Hello, everyone. I've got a basic water material w/ displacement for caustic refractions. This seems to be working, in general, but I'm seeing an unexpected 'cutoff' where the lighting on the bottom of the pool suddenly changes along a line.

In the past, I've had issues w/ the caustic Photon Radius setting, where the entire model needs to be relocated to the -x,-y quadrant with respect to the default model origin. In those cases, where part of the water surface is out of that quadrant, and part is in, I've seen this line. But obviously the caustic effect is being applied to both the lighter and darker ends of the pool in this image...

I've got a dome light (spherical HDRi sky) and the Sketchup sun at .3 providing the light.

Any ideas? Let me know if more information is needed.

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Re: Refractive Caustics (Pool Water) - Weird Cutoff?

Postby filibis » Wed May 10, 2017 11:38 pm

Can you share your water material settings?

I would suggest increasing Photon Emit Radius under Sun options but you already mentioned and aware of that. Maybe try disabling Affect Shadows parameter of water material?

Check the official manual, you might get a clue: ... P/Caustics ... C+SunLight

And make sure that there is no invisible plane or something contributing to the shadows etc.
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Re: Refractive Caustics (Pool Water) - Weird Cutoff?

Postby saberopus » Fri May 12, 2017 3:40 pm

Thanks, filibis. Here are the material settings:

Nothing in the manual has clued me in to a solution, yet. I am going to try disabling Effect Shadows now.
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Re: Refractive Caustics (Pool Water) - Weird Cutoff?

Postby saberopus » Fri May 12, 2017 9:43 pm

Well, uh, it seems I've solved the problem by shifting the entire contents of the model to the -x,+y quadrant w.r.t. the default origin. Why this works, I don't know... nor do I know why the cutoff was where it was before, because it did not occur along one of the default axes, but at something like a 45 degree angle between -x and -y.
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Re: Refractive Caustics (Pool Water) - Weird Cutoff?

Postby nowd1976 » Tue Oct 09, 2018 9:59 pm

Hi, everybody. I have a fundamental water material w/uprooting for acidic refractions. This is by all accounts working, when all is said in done, however I'm seeing a surprising 'cutoff' where the lighting on the base of the pool all of a sudden changes along a line.
Just check polygroup summer waves elite pool


Re: Refractive Caustics (Pool Water) - Weird Cutoff?

Postby freebs » Thu Feb 07, 2019 3:05 pm

TL;DR version:
Go into LIGHTS -> Sunlight -> Caustic Photons and change the EMIT RADIUS there. The units are in your model units. And the center starts from the sun's location.

Full explanation:
Vray projects a beam with an 'Emit radius' when rendering caustics. Where that edge ends, you'll see a cut-off line.
In 3ds max you can set this emit radius' direction and size visually. Buuuht, not here.

In Sketchup the sun is the emit source, so depending on time of day(!) you'll have to fiddle with the emit radius.

The attached image has three swimming pools: at 34' from the origin of the blue axis (0,0,0), then again at 60' and again at 90'.

At 1:00pm the sun catches all the pools nicely, but the 2d and 3d pools aren't getting enough caustic photons to show caustics properly (top half of image), because the emit radius is set to 700, which doesn't extend far enough.

NOTE: The units of this model is inches, so that's 700 INCHES or 58.3'. The yellow circle has a 59' radius, and you can see the 'dark line' cutting through the pool.

The second render shows the emit radius set to 1080" (90'). This time the third pool is captured and begins to render caustics.



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