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[Glaiel-Gamer]

Anyone know how to do a good underwater effect?


This is what I have so far and well... it's less than favorable and quite hilarious when you jump in the water and hear the music go BEOOOOOO000000000WWWWWWWWWWWwwwwwwwwwww..........

(this piece of code will be called at ~120Hz when there is distortion)

Code:

void syncMusic::setDistortion(float amount){
  distortion = amount;
  float val = 1.0;
  if(distortion > .1){
    val = 1.0 - random(0.8, 1.0)*distortion * .4;
  }
  for(int i = 0; i<tracks.size(); i++){
    alSourcef (tracks[i]->Source, AL_PITCH, val);
  } 
}

[Ivan]

I'm guessing you'd want reverb... I think OpenAL has an EAX extension for reverb, but since it's EAX, it only works on windows.

[John Nesky]

Don't distort the pitch. Run it through a lowpass filter instead. And yeah, reverb might help too.

[raigan]

Yeah, I think just a low-pass filter should do it.

[Glaiel-Gamer]

Yeah, I think just a low-pass filter should do it.

any links for how to do this in openAL?

I prefer to keep dependencies to a minimum

[ஒழுக்கின்மை (Paul Eres)]

you could just have two sets of sound effects: above and below water. run all your sounds through a low pass filter in audacity, and create separate sound files for each sound. then just switch to those when the player goes underwater.

[Glaiel-Gamer]

you could just have two sets of sound effects: above and below water. run all your sounds through a low pass filter in audacity, and create separate sounds for each sound. then just switch to those when the player goes underwater.

I'm talking about background music and considering I have 5 tracks of music per "song" (~20-30 MB per song) I don't want to end up doubling that

[ஒழுக்கின்மை (Paul Eres)]

ah, understandable.

another option is just to quiet it. simply reducing the volume suddenly can given an interesting effect.

[Glaiel-Gamer]

ah, understandable.

another option is just to quiet it. simply reducing the volume suddenly can given an interesting effect.

I kinda want some funky effect

I had this right now
http://www.youtube.com/watch?v=0ELUuncInPQ#t=8m41s

That was using one of the 5 tracks as a "water" track and he put some funky staticy chords in it to layer on top of the other 5.

I'm changing that since water isn't really common enough to warrant wasting a whole audio track for, and I decided to add another one in somewhere else and free up the space used by the water track by using a filter instead. I don't want to use 6 tracks either, I'm already pushing it trying to stream 5 oggs at a time and the filesize can't really afford it especially when i add more songs in

[ஒழுக்கின்மை (Paul Eres)]

i can't really tell the difference between underwater and not there, although that could be because of youtube's poor sound quality

[Impossible]

Yeah, I think just a low-pass filter should do it.

any links for how to do this in openAL?

I prefer to keep dependencies to a minimum

I don't think its possible in a cross platform way in OpenAL. OpenAL is a really shitty audio API...

[Zaphos]

EFX is supposed to be the portable equivalent to EAX for OpenAL and should let you do low pass filters and reverb -- there are samples in the OpenAL SDK for this, and a doc called "Effects Extension Guide.pdf" that might help.

edit: EFXFilter.cpp in the sdk specifically seems like what you might be looking for.

[BlueSweatshirt]

Yeah, I think just a low-pass filter should do it.

any links for how to do this in openAL?

I prefer to keep dependencies to a minimum

I don't think its possible in a cross platform way in OpenAL. OpenAL is a really shitty audio API...

What would you recommend instead of OpenAL? All I know of myself is FMOD, but that comes with a pretty nasty license if you want to make any profit from your product.

[Glaiel-Gamer]

Yeah, I think just a low-pass filter should do it.

any links for how to do this in openAL?

I prefer to keep dependencies to a minimum

I don't think its possible in a cross platform way in OpenAL. OpenAL is a really shitty audio API...

What would you recommend instead of OpenAL? All I know of myself is FMOD, but that comes with a pretty nasty license if you want to make any profit from your product.

I'm personally still using openAL since i really like it and I get myself some nice low level access to the sound and it's free.

I was not asking for alternatives to it anyway, or for opinions on the library, but looking for specific help within the library

[mcc]

If you're going to be working with raw sound values, as in OpenAL, it might be worth it to learn how to do low pass/high pass/LTI filters for real.

As I remember though you can actually do a cheapo low pass filter by doing a "weighted moving average". All you really have to do, each time you write a sample, is average it with previous samples. So do something like this:

#define WEIGHT 0.1
inline float ugly_lowpass(float in) {
static float last = 0;
last = in*WEIGHT + last*(1-WEIGHT);
return last;
}

Then run ugly_lowpass(x) sequentially on every sample you send to the sound card.

As I understand if you sit down and do the math this turns out to be equivalent to a low pass filter done "correctly".

http://lorien.ncl.ac.uk/ming/filter/fillpass.htm

EDIT: Some random thoughts on this code snippet: The closer to 0 the WEIGHT number is the heavier the low pass will be. Also the heavier the low pass is the progressively quieter the output will be. If this isn't what you want may want to compensate by turning up the volume, or adding echo. I think low pass + echo will give you something very much like the cliche "video game underwater effect".

[John Nesky]

MCC is on the money here, you can roll your own low pass. More example code over at the wikipedia article:
http://en.wikipedia.org/wiki/Low-pass_filter#Algorithmic_implementation

[Ivan]

Yeah, I think just a low-pass filter should do it.

any links for how to do this in openAL?

I prefer to keep dependencies to a minimum

I don't think its possible in a cross platform way in OpenAL. OpenAL is a really shitty audio API...

What would you recommend instead of OpenAL? All I know of myself is FMOD, but that comes with a pretty nasty license if you want to make any profit from your product.

Really? I find FMOD's license to be quite reasonable.

[Zaphos]

MCC is on the money here, you can roll your own low pass. More example code over at the wikipedia article:
http://en.wikipedia.org/wiki/Low-pass_filter#Algorithmic_implementation

Would you recommend this over just using the built in filter functions?

[John Nesky]

I have never used OpenAL, so I can't comment on its built-in filter functions. A lowpass filter is super easy to implement, though, as long as you have convenient access to your audio sample data.

[bateleur]

Really? I find FMOD's license to be quite reasonable.

The licence info appears to suggest a four digit cost even for an indie game. Whether it's "reasonable" or not, it does seem high for an audio library and I can understand any developer who felt they'd rather avoid that expense.