View Full Version : Reflection on Water Surface?

08 August 2011, 05:17 PM
i'm trying to create an image (photo) reflected on water surface.
im making water surface with a bump map,
but don't know what shader to use to make the reflection realistic.

p.s. maya/mental ray preferred, but general answers are also helpful.

08 August 2011, 12:26 PM
All you need to do for water is make sure you have a fresnel falloff on your specular reflections with an IOR of ~1.34. The rest is all down to your bump/displacement technique.

08 August 2011, 01:30 PM
If you're trying to make an image like the one you posted you could create any basic material with 100% reflectivity and then apply a bump map.

But to be accurate use the mia_material with playmesumch00ns suggested settings.

08 August 2011, 10:03 AM
thank you for your replies.
however, i am not getting the result i want.

this is the original render.
then, i added another plane for my reflected image (only visible in reflection).
then i addd mib_reflect node.
and the result.

the reflected image is not as strong as i want, and the bump is gone.
reflectivity on water is set to 1.
i can't find fresnel falloff attribute.
what am i doing wrong? :rolleyes:

08 August 2011, 12:25 PM
There are two major problems with your setup here.

1) You appear to be putting your reflection source directly above the water? What exactly are you trying to achieve by doing this? You need to have your reflected image source on a skydome surrounding your scene, or at least on geometry that forms a portion of it.

2) Your reflection image looks like it's LDR. You need a HDRI if you're going to make the water look real.

08 August 2011, 01:51 PM
thank you for your reply.

i tested an HDRI environment map on a sphere, which worked fine.

but the image i want to reflect is a LDR plain photo.

i also rendered reflection as a different pass (on a blinn) and added the pass as screen.
looks a bit cheesy.

let me know if you come up with any other way.

08 August 2011, 07:14 PM
I think it needs more contrast, it might be the sun and sky exposure blowing it out. Also lets look at the reference, the trees in the reflection right at "magic hour" making them almost black while there is still daylight...that's what makes that image. I would get some more reflections in there, maybe something dark below the surface to give it that deep blue look.

I could be wrong, nothing but pros above me posting, I would follow their word over mine.

08 August 2011, 11:54 PM
First, ditch the Blinn unless you're using Maya's software renderer.

Also, no need for mib_reflect or anything like that. Just use the mia_material_x.

You can get away with reflecting your image without a skydome, but you should be using a linear lighting workflow regardless. The last few renders don't appear to be linear.

Since you're working with such a simple setup, I'd sculpt that plane instead of relying on a bump map. Basically, use a displacement map instead, or run that bump as a displacement. Then it's not just software trickery, but actual geometry helping with your reflections.

Keep at it, you'll get it soon!

08 August 2011, 02:03 PM
Linear workflow and HDRIs will get you closer to a realistic look but you can get there too without, like in the old days :)

First off, like playmesumch00ns says, look up a way to add some fresnell falloff. If it's not in your shader you'll have to make it yourself. The effect should be that your geometry reflects more at glancing angle and little when viewed straight on. See in your reference picture how the sky alternates between light and dark along the ripples? That's the result of the effect; the sky reflects less as you view the ripple straight on. This is another reason why it may look better if the waves are actually modeled.

Secondly you have to boost your LDR image into pseudo-HDR. You can cheat this with contrast and intensity nodes on your sky texture but you'll have to rely on your eye to make it look good.

But what are you rendering your reflection as a separate pass for? Or rather what are you screening over? If you for some reason want to comp it your base color needs to be rather dark, somewhere between black and dark green or brown for slightly murky water. Otherwise your reflections will turn washed out.

Arild Anfinnsen

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