Comments on: Regarding Water

By: Tomas

Tomas — Sat, 16 Mar 2013 21:29:26 +0000

In reply to Zaphos.

Oh, right! Thanks!

I don’t know too much on the subject, so I couldn’t verify the sheets anyway, but this looks an awful lot more like the youtube vid. I see the other slides aren’t even public anymore.

By: Phil Fortier

Phil Fortier — Sun, 02 Sep 2012 05:52:40 +0000

I tried my hand at implementing the Valve technique. From my understanding, the repetition issue can be addressed just by using different normal maps for each of the two samples you take.

As for the pulsing, it is a trade-off between reduced pulsing and increased distortion. You have to tweak the values to get something that looks decent. I put my findings here:
http://mtnphil.wordpress.com/2012/08/25/water-flow-shader/

I’m also going to try the tiling method. My concern (other than the performance considerations for 8 texture samples per pixel) is that it requires using the same flow vector over the entire tile. This means sharp turns in water direction won’t look as good, and you won’t be able to get swirls and whirlpool-type effects (which are very easy with the Valve method). On the other hand, it will probably look better in more “open” water.

By: Zaphos

Zaphos — Wed, 29 Aug 2012 04:02:07 +0000

In reply to Tomas.

fwiw those slides don’t explain the technique in the video; they seem more just a general overview/intro of fluid simulation.

Here are slides that are specifically on the technique in the video: http://www.matthiasmueller.info/publications/tallCellsSlides.pdf
And the paper: http://www.matthiasmueller.info/publications/tallCells.pdf

By: Ignacio

Ignacio — Mon, 27 Aug 2012 05:22:09 +0000

@David, @Mark: Thanks for sharing these resources. I was not aware of Kyle’s example and the tiling method looks very promising!

By: David

David — Sun, 26 Aug 2012 21:00:57 +0000

In reply to Pritchard. Sorry about that :)

By: Pritchard

Pritchard — Sun, 26 Aug 2012 20:52:19 +0000

In reply to David. At a glance, I thought you were David Thier. Wouldn't I have been surprised...

By: John

John — Sun, 26 Aug 2012 16:41:05 +0000

Overall an interesting read, thanks for sharing.

I’ve worked with a water system before where screen-space depth difference was used for a few things, including blending between “deep” and “shallow” colours, fading out real time shadows, and alpha fade. I was never happy with any of this, the dependency on view angle caused it to always break down in some conditions no matter how much you tweak it. For foam in shore regions with underlying terrain I’ve found height above terrain works well with a scrolling mask texture to break it up, but for a more general solution to cope with bits like the pier in your screenshot I reckon you’re best to store it in a texture like you say, if you can afford one with sufficient resolution.

By: bitbof

bitbof — Sat, 25 Aug 2012 17:10:23 +0000

The wet stones are a nice detail. Makes it feel less like everything has a water repellent surface as in most games.

By: Milad Thaha

Milad Thaha — Sat, 25 Aug 2012 13:12:28 +0000

I don’t know squat about programming, but this was fun to read! Thanks for letting us readers look into your developments. :)

By: Mark Wayland

Mark Wayland — Sat, 25 Aug 2012 12:34:58 +0000

Thanks for sharing your experiences. This resource on flow maps and the repitition issue may prove to be useful:
http://graphicsrunner.blogspot.com/2010/08/water-using-flow-maps.html

By: Tomas

Tomas — Sat, 25 Aug 2012 10:29:49 +0000

I really like these graphic progression features. Especially on water. Water simulation keeps on being something that’s hard to calculate, we cannot even fully do it, it remains approximation.

Will the water in the witness be interactive? Or are you just modeling the surface and tweaking other visual aspects to make it look good.

Here’s another set of lecture slides on a method of programming real-time fluid behaviour that might be interesting. http://graphics.ethz.ch/teaching/simulation11/lectures/Fluids1.pdf
Seen in this video: http://www.youtube.com/watch?v=Jl54WZtm0QE

By: justin

justin — Sat, 25 Aug 2012 10:15:05 +0000

I like how you guys put a lot of time and effort into making physical phenomena and properties realistic for the game. Most games care about getting the muscles of a character right or the shininess of a gun or facial expressions with motion capture. Never seen a game that cares to be realistic where it counts: In its architecture, geography, topography and properties of elements in the world.

And the thing is that is not bullshit! The stuff is realistic in a way that this is how things work in the real world! And its actually stuff that matters in the game and you can use and interact with.

Capcha: harsh comment

By: David

David — Sat, 25 Aug 2012 08:41:17 +0000

You should check this solution http://www.rug.nl/cit/hpcv/publications/watershader/index where most of Vlacho’s problems were solved.
Cool to see how you guys have approached the water implementation. :)
Will the player be able to interact with the water? If so, how are you guys going to handle the changes done to the flow? (I’m asking because I’ve been working exactly on that)

By: Andrew Russell

Andrew Russell — Sat, 25 Aug 2012 07:48:18 +0000

Your screenshots have always been impressive. But these latest ones, with the new water, seem to have taken on some new quality (is it added realism? perhaps exiting some kind of uncanny valley?) that makes them look amazing!

By: Sean Hogan

Sean Hogan — Sat, 25 Aug 2012 06:55:30 +0000

I think it’s neat how the programmers in graphics create publications and share techniques with eachother. Heavy graphics programming seems like quite the adventure, thanks for this look into your developments.

By: d

Sat, 25 Aug 2012 06:32:56 +0000

I have to say I quite enjoy the environmental storytelling you’ve done with the fort (intentional or not).