"Mark Birch" <las### [at] hotmailcom> wrote in message 
news:web.435f46043a58c1498557c1c80@news.povray.org...
> Image looks terrific, but putting a CSG lens with IOR in front of the
> camera?
> Ouch! what does that do to your render time?

Oh that's not too bad, I'm sure in a scene with a lot of objects I'd take a 
hit for destroying the vista buffers but in this scene it's not too bad. 
It's the dispersion and focal blur that really kill it! Though I've decided 
I can get away with lower focal blur settings because the dispersion kind of 
hides the noisiness.

> 1. I tend to use ultra_wide_angle camera instead of perspective camera to
> get the 'bent horizon' effect, should work alot faster than rendering
> through a lens.
>
> 2. Can't help you with the dispersion (which works pretty well with the 
> sun
> in the top left hand corner), but MegaPOV's post-process functions might 
> be
> able to duplicate/approximate this.

I'd rather do it properly at the moment. This is more of an exercise in 
finding photo-real techniques, not really trying to come up with efficient 
implemenrations. I'm pretty sure a 2D filter could give a good approximation 
to all of these effects but I wanted to stick to pure ray-tracing. In fact 
maybe I'll add a micro-normal and internal-reflections to the lens to get 
some nice lens flares... (okay now that would be overkill!)

> 3. Focal blur would be easier to tweak without the lens.

True, but the lens means the focal point is not constant for the whole 
image, which gives a very natural look (it blurs more at the edges).

> 4. 'Vignetting' could be done using a transparent disc with onion pattern 
> in
> front of the camera, or perhaps as part of a post-process function.

Well I'm already doing that with just a transparent pattern (cylindrical 
pattern in fact). I couldn't think of a way to get pov to simulate the real 
effect, which I believe is due to the shallow angle of the light hitting the 
edges of the film when using a wide-angle lens. Pov doesn't really simulate 
film so I just cheated.

> Not saying what you've done is bad, just trying to suggest some ways to
> speed up a good effect.

Suggestions are appreciated. I certainly plan to take what I've learnt and 
use it on future projects in more subtle and, like you suggest, more 
efficient ways.

Tek
http://evilsuperbrain.com

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