Underwater refraction how?

[Squeak]

After seeing real-time refraction of underwater textures and geometry, (and warping of reflections on the water surface), in games like WR. Blue Storm, Super Mario Sunshine and ICO, I’ve been wondering a bit about how it is done technically.
I mean how does the CPU “knowâ€￾ how to “warpâ€￾ the texture at the correct places at the right angle between the viewpoint and the waves?
The only solution I can think of, is some kind of raytracing algorithm, but wouldn’t that be way to resource demanding on today’s hardware?
A not to technical answer would be appreciated, or a link to one.

 

[Panajev2001a]

Sometimes it doesn't...

What is done usually takes into account the view angle and that determines if the water is more reflecting or more refracting ( water being transparent refracts water until the ray of light hits with a certain incident angle, after that the water appears like a "perfect" mirror ) this can be done by casting some rays from the view point to approximate a realistic looking surface.

As far as the refraction itself, soemtimes it is done through texturing/blending tricks more than calculating exactly the coefficient ofrefraction even if mixing with the approach I mentioned before you could make several "areas" with different ( pre-calulated ) refraction index ( and refraction properties ) and use that for calculations...

I hope my brain was not turned off while I wrote this post, I hope it males some sense...

 

[mr]

If you like a more technical information gamasutra provides a good read. Even if you skip the math you should get the idea.

Other articles are listed here where you can also download a demo.
Great stuff!

 

[Tahir2]

...I hope my brain was not turned off while I wrote this post, I hope it males some sense...

Only that part didn't make any sense.

 

[LogisticX]

Well, this is the field I'm moving into and I must say that I'm a little intimidated by the methods as to how these little "tricks" are done. Thanks for the links though "mr".

 

[overclocked]

Must ask this while still on water.. Is WR-Blue storm a good game, woth bying, i saw it new pretty cheap and thought of bying it beacause i really loved the first game. Then thers splashdoen, and a follow op i´ve read.
Any that can compare "New" waverace against old and maybe someone of you played splashdown.

 

[zurich]

Must ask this while still on water.. Is WR-Blue storm a good game, woth bying, i saw it new pretty cheap and thought of bying it beacause i really loved the first game. Then thers splashdoen, and a follow op i´ve read.
Any that can compare "New" waverace against old and maybe someone of you played splashdown.

Well, I was a massive fan of WR64.. played it in and out ad nasuem (but in a good way!), and couldn't stand WR:BS... like not at all. Controls, physics, gameplay.. blech. If anything, WR64 got a 9/10 from me and WR:BS got a 6 (tops).

 

[overclocked]

Well, I was a massive fan of WR64.. played it in and out ad nasuem (but in a good way!), and couldn't stand WR:BS... like not at all. Controls, physics, gameplay.. blech. If anything, WR64 got a 9/10 from me and WR:BS got a 6 (tops).

Ok then i skip it, was it nintendo that did Bluestorm also?
Yeah i now what you mean, really loved that game because of wonderful waves, still in my mind "nice looking water and the tracks. It was just FUN! Heard of a "real" new Wave Race being developed or?

 

[Squeak]

Thank you for the feedback so far.
So it isn´t magic after all...