<p>One way that might work is to have boids but render each boid as a group of birds.  This way the simulation is still simple but the rendering makes it seem complex.  You might even allow a little drift per bird in the boid to make it look so obviously rigid.</p>

CC BY-SA 3.0
2015-08-21T15:41:40.173Z
2015-08-21T15:52:48.360Z
2015-08-21T15:52:48.360Z
Alan Wolfe
<p>I'm not sure if this counts, but you can use fluid dynamics to render large crowds (of birds, people, etc). With SPH (smoothed particle hydrodynamics) to model the "fluid", you aren't really describing the motion of each bird per-se, since you can sample the crowd of birds with a representative set, and then draw birds around your samples. Take a look at this paper that compares the different methods:</p>

<p><a href="http://gamma.cs.unc.edu/lookahead/golas-2013-hybridcrowd.pdf" rel="nofollow">http://gamma.cs.unc.edu/lookahead/golas-2013-hybridcrowd.pdf</a></p>

CC BY-SA 3.0
2015-08-22T12:28:39.017Z
This is actually a pretty good method. But is it less expensive?
joojaa
CC BY-SA 3.0
2015-08-22T16:02:29.190Z
It's as expensive as you want your simulation to be. If it's *too* expensive, use fewer samples.
Mokosha
CC BY-SA 3.0
2015-08-22T08:02:39.787Z
2015-08-22T08:02:39.787Z
Mokosha
<p>Although simulation models like <a href="https://en.wikipedia.org/wiki/Boids">Boids</a> give good results for bird flocks or fish shoals on a small scale, simulating every single member in real time becomes unrealistic for huge numbers. Is there a way I can model a flock in the distance where only the density of birds is visible? I'd like to have that flowing, changing density gradient with a much smaller number of variables to process.</p>

<p>I've tried using a much smaller population and displaying each boid as a blurred area with Gaussian density so that as they overlap the density rises and falls through their interaction. This is reasonably cheap but it never leads to sharp changes in density, either spatially or temporally, which makes it look too uniform.</p>

<p>Is there any other way of getting away with a much smaller number of individuals? Or is the only way to get realistic results to prerender?</p>

CC BY-SA 3.0
2015-08-22T15:20:44.137Z
It would be great if you had reference footage for the effect you want. Say, something like this? https://www.youtube.com/watch?v=XH-groCeKbE
John Calsbeek
CC BY-SA 3.0
2015-08-22T15:24:42.263Z
@JohnCalsbeek yes that would make it easier to get across what I want. In the video you linked to the individual birds are discernable (just). I'm looking to render a flock a little more distant so that individuals are not visible, but the variations in density are still consistent and realistic.
trichoplax is on Codidact now
<real-time>
Is there a way to achieve the look of a distant flock or shoal without full simulation?
trichoplax is on Codidact now
# Is there a way to achieve the look of a distant flock or shoal without full simulation?

(Asked by: username_0 on 2015-08-21)

Although simulation models like [Boids](https://en.wikipedia.org/wiki/Boids) give good results for bird flocks or fish shoals on a small scale, simulating every single member in real time becomes unrealistic for huge numbers. Is there a way I can model a flock in the distance where only the density of birds is visible? I'd like to have that flowing, changing density gradient with a much smaller number of variables to process.

I've tried using a much smaller population and displaying each boid as a blurred area with Gaussian density so that as they overlap the density rises and falls through their interaction. This is reasonably cheap but it never leads to sharp changes in density, either spatially or temporally, which makes it look too uniform.

Is there any other way of getting away with a much smaller number of individuals? Or is the only way to get realistic results to prerender?

**Tags:** real-time

> **Comments:**
> **username_1**: It would be great if you had reference footage for the effect you want. Say, something like this? https://www.youtube.com/watch?v=XH-groCeKbE  
> **username_0**: @username_1 yes that would make it easier to get across what I want. In the video you linked to the individual birds are discernable (just). I'm looking to render a flock a little more distant so that individuals are not visible, but the variations in density are still consistent and realistic.  

---

## 2 answers

### Answer by username_2 on 2015-08-21. Score: 4

One way that might work is to have boids but render each boid as a group of birds. This way the simulation is still simple but the rendering makes it seem complex. You might even allow a little drift per bird in the boid to make it look so obviously rigid.


---

### Answer by username_3 on 2015-08-22. Score: 4

I'm not sure if this counts, but you can use fluid dynamics to render large crowds (of birds, people, etc). With SPH (smoothed particle hydrodynamics) to model the "fluid", you aren't really describing the motion of each bird per-se, since you can sample the crowd of birds with a representative set, and then draw birds around your samples. Take a look at this paper that compares the different methods:

<http://gamma.cs.unc.edu/lookahead/golas-2013-hybridcrowd.pdf>

> **Comments:**
> **username_4**: This is actually a pretty good method. But is it less expensive?  
> **username_3**: It's as expensive as you want your simulation to be. If it's *too* expensive, use fewer samples.  

---

