One of the poster’s mentioned Snells Window (http://en.wikipedia.org/wiki/Snell’s\_window). I was wondering what some best practices would be here for getting the most realistic underwater render possible. I realize post work can really cut down time and effort, but I was hoping for any tips or advice on doing most of it in renderer.
I’ve been using vray for work for almost 8 years now, and to be honest I’ve only rendered on the top side of water, not under. So I really don’t know where to begin. Thanks for any ideas!
EDIT: Added a question: Would you create a volume to put the camera in (like a box or something) or should the water just be a plane? If it’s just a plane, how does that work? If not, also.. would you want to use the VrayMtl translucency? Thanks for any help!
To get an optical manhole just take 1/the ior. 1/1.34 = 0.7462686567164179. try that. And yes as you are in the medium I would just have the surface as a plane.
Here is a quick test using the above water material with displacement, Hdr lighting and Vrayenvironment fog.
-ive done some murky underwater animation in the past. a box for the water volume with the normals flipped. displaced plane for the seabed, some pointcached wavy seaweed dotted around.
i used the “blend” aa filter. looks just right in an underwater setting.
a few particle systems for debris and plankton etc, and a direct light, with a looping “caustics generator” map and vray env. fog for those lovely caustic rays. some motion blur and depth of field, then a blurred moonlit hdri in the env slot.
the scene was focused mainly on the sea bed.. ill see if i can dig out some stills but it was a long time ago.
You’ve got me hooked on trying to achieve this ‘optical manhole’/snell’s window thing now Deflaminis, I’ll post my findings
I’ve got my water’s ior set to .75 and while I am getting an awesome looking underwater render, snell’s window is eluding me. I don’t really want to try any fake’s, I’m going to let Vray seduce me with it’s accuracy (or so I hope)
Cheers Vlado, the normals are indeed pointing towards the camera, still can’t get Vray to show me Snell’s window, can get it in Maxwell/FryRender but not quite cracked it in vray as yet, the atmospherics, caustics and dispersion look amazing though (will post something at a later date)
There’s a link with some info here in case anybody wants to see what happens in reality
Works fine for me… I didn’t flip the normals on the surface though, I just wrapped the camera in a bubble with inverted normals and kept the material IOR to 1.33
That’s awesome thanks for your help on that, and the scene file
Just out of curiosity, could you explain the logic behind placing the camera inside a bubble/sphere? It works perfectly but I probably wouldn’t have ever considered this approach
Because of the fog color that I used in the VRayMtl material, which is the same material on both the bubble and the water surface; otherwise V-Ray won’t know when to start and stop the fog. It also helps V-Ray to compute the correct IORs. Think of it like a real-world underwater camera case
Wow step away for a weekend and there is 2 pages of posts! (My face is red.)
Thank you all for posting, I’ll have some time here Wed to play with this a bit and learn more about things in this regard. Thank you all again for posting.
EDIT: To make sure I understand how Vlado got what he did, it’s basically a sphere object around the camera, inside the box volume?
anchovy: That’s pretty amazing, this might seem like a lame question but how did you know to do that?
I did a number of underwater shots when I was a TD at the Orphanage. We used Brazil there but the premise is the same. I admit I like Vlados suggestion and I want to try it here in a bit.
It works as well as Vlado’s image suggests, little bit of noise or displacement on the water and some objects above it (and HDR environment of course) and it really comes to life. Just adding a seabed to my scene which should reflect beautifully in the area outside of snell’s window, with some caustics as well this should turn out nicely
Thanks everyone who posted here, it’s a great lot of information.
I started setting up the scene last night for a bit after work (late), got the water volume in, a sun/sky and a vray cam. I tried to get some fog color for the water material into my volume but it was acting very odd, even the slightest value in the fog color would send it totally saturated extreme color, or black. No in between, even trying .001 for fog mult. I’ll get back to it tonight, but I’m guessing the problem was the lack of a bubble for the camera, and when the cam is in the volume without the bubble it seems to act differently than I’d expect. I tried turning off the scale option as well, but no go.
Don’t have to work late tonight so going to make some progress, thanks again for all your help.
Hi Deflaminis, try the water as a surface rather than a volume. When the camera is within a bubble, the void between the water and the bubble will become your volume (hope that makes sense)
This will ensure that your fog and ior work correctly, this is what I gathered from Vlado’s sample scene (definitely worth downloading)
Hi Richb, thanks for the post. I downloaded the checked out that scene file you mentioned, it’s amazing in its simplicity, yet I find I don’t fully understand why it works. It’s pretty amazing if the distance between the bubble and the plane for the surface of the water can be viewed by vray as if it was a volume. Again, I never would have expected that.
Bear with me here as I try to reason my way through this. Since the bubble *and* the surface have the same material on them, and since they are both single sided geometry, Vray thinks that the fog color is based on the space in between them? (Amazing.) The conclusion I’m drawing (and maybe improperly) is that Vray doesn’t care if a volume (or in this case surfaces) are “water tight” or closed. It just sees that there is distance between the two surfaces and since they have the same fog settings will go ahead and draw/render the fog even though they are separate objects. Is that close? (I’m having a hard time articulating what I mean here.) Regardless, I never would have guessed that or tried anything like it. (I realize that’s basically what you posted, I’m just trying to figure out why it works.)
Oddly, if I duplicate the material and put the copy on the plane but not the bubble, it stops working. (Or maybe that isn’t odd, but I don’t understand why.) The dupe can have the exact same settings but it won’t fly.
Even stranger (to me) is that if I use a plane instead of a bubble, the effect breaks. instead of going black around the edges, it goes white. So there is something about actual curvature of the ‘bubble’ that makes this work. Is it possible this relates in part to the normal curvature of a lens? Also odd, is if I flip the bubble-replacer-plane so that the normals point toward the camera, I still get fog but the black around the edges is now just normal fog, though I still get a nice window in the center.
And even more curious is the effect of a plane with a bend modifier has on the surface of the water, it can start to look even a bit cloudlike.
I’m so glad I started this thread, I feel like my vray knowledge (outside of commercials and viz) is increasing quite a bit. Thank you everyone for your time posting here and helping me figure this stuff out. I really appreciate it.
Here’s a screen of the plane with bends on it instead of a sphere. Notice the swirly striations on the surface, almost like a post effect. Working as intended I’m sure, just cool and curious.
There are some things I am having trouble wrapping my head around too so you’re not alone, I’m just happy that it works but I’m just like you in wanting to find out ‘why?’
Vlado said earlier in the thread that the bubble and the surface work together to return the correct refractive amount, as per the IOR (1.333) (though he used different words)
Not sure why swapping the bubble for another plane would break the setup, only thing I can think of is make sure the normals of the plane face the camera, the normals for the water’s surface should remain facing away from the camera
I have somewhat of a better logical explanation in my head as to why this setup works but I’m having trouble knowing where to begin explaining it
Check the normals and try it again, I’ll fire up the pc and try it too cos I would like to know if my understanding of this scene is correct
Ant
*Just re-read your post and I must have missed the bit where you had tried flipping the normals, I’m still gonna mess with the scene to test what makes it/breaks it
