Hi everyone,

I want to create a realistic looking image with all the camera artefacts
introduced into it e.g. noise, vignetting, bayer demosaicing, anti-aliasing. And
I'd like to add the noise in proportion to the number of photons hitting the
pixel. This is to simulate exposure tuned images that is the noise at the
high-frame rate images should be more than the noise at low-frame rate images.
Is it possible to do it using povray without too much time expense?

While anti-aliasing can be done using the +A option but in my case it takes
enormous amount of time because the scene is really complex. The other option is
to create a super resolution image and then downsample it, but are there any
other better ways to do it?

I'm totally clueless about vignetting and bayer demosaicing. Is it possible with
povray?

It would be really helpful if someone can help me with generating these
realistic looking povray images with real camera artefacts!

Thanks for your patience.

Post a reply to this message

> Hi everyone,
>
> I want to create a realistic looking image with all the camera artefacts
> introduced into it e.g. noise, vignetting, bayer demosaicing, anti-aliasing. And
> I'd like to add the noise in proportion to the number of photons hitting the
> pixel. This is to simulate exposure tuned images that is the noise at the
> high-frame rate images should be more than the noise at low-frame rate images.
> Is it possible to do it using povray without too much time expense?
>
> While anti-aliasing can be done using the +A option but in my case it takes
> enormous amount of time because the scene is really complex. The other option is
> to create a super resolution image and then downsample it, but are there any
> other better ways to do it?
>
> I'm totally clueless about vignetting and bayer demosaicing. Is it possible with
> povray?
>
> It would be really helpful if someone can help me with generating these
> realistic looking povray images with real camera artefacts!
>
> Thanks for your patience.
>
>

To reproduce the noise associated with emultion, you can use jitter for 
every area_light. In that case, keep the light array density relatively low.
Adding crand with a large value will also add a fair amount on noise. It 
could be interesting to play with crand using a negative value. Normaly, 
crand darken some random pixels.
Be warned that both don't realy play nice with anti aliasing forcing it 
to kick in much more frequently.

The vignetting is a progressive darkening as you get away from the 
center of the image. You can do it using a spherical pattern and the 
macros from screen.inc.

If you add a lense shaped object just in front of the camera, you can 
easily add some realistic chromatic aberation and also some distortion.
Add: interior{ior 1.1 dispersion 1.01} to the lense object.

Not touching everything you mentioned, but giving somewhere to start 
looking.




Alain

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Am 13.02.2011 17:36, schrieb handos:

> While anti-aliasing can be done using the +A option but in my case it takes
> enormous amount of time because the scene is really complex. The other option is
> to create a super resolution image and then downsample it, but are there any
> other better ways to do it?

For anti-aliasing, there is /absolutely no/ substitute for oversampling, 
i.e. shooting multiple rays per final-image pixel. Whether you achieve 
that by (a) high-resolution rendering and subsequent downsampling, (b) 
any of POV-Ray's anti-aliasing modes, or (c) focal blur is up to you; at 
any rate, rendering at high resolution and then downsampling is always 
the most time-consuming variant of the three, for any given level of 
quality, as it will shoot the same number of rays for each final-image 
pixel, while the other variants will shoot fewer rays where 
anti-aliasing is not needed.

> I'm totally clueless about vignetting and bayer demosaicing. Is it possible with
> povray?

For vignetting, you could place a slab in front of the camera, with a 
texture that fades from totally transparent black at the center to 
almost-but-not-quite transparent black towards the edges.

As for demosaicing, I had to look up what that even is. Actually, the 
"root artefact" would be "Bayer mosaicing", with demosaicing being an 
attempt to compensate for that effect. For this, you'll probably need a 
postprocessing tool (though you might be able to use a second POV-Ray 
pass for this, using an orthographic scene). The following procedure 
might come close enough to the real thing:

Using a double-resolution output image, ...
- offset the R channel horizontally by 1 pixel
- offset the B channel vertically by 1 pixel
- average the G channel with a copy offset both horizontally and 
vertically by 1 pixel
- Downsample the image to 50%.

Post a reply to this message

On Sun, 13 Feb 2011 18:36:12 +0200, handos <han### [at] gmailcom> wrote:

> Hi everyone,
>
> I want to create a realistic looking image with all the camera artefacts
> introduced into it e.g. noise, vignetting, bayer demosaicing,  
> anti-aliasing. And
> I'd like to add the noise in proportion to the number of photons hitting  
> the
> pixel. This is to simulate exposure tuned images that is the noise at the
> high-frame rate images should be more than the noise at low-frame rate  
> images.
> Is it possible to do it using povray without too much time expense?
>
> While anti-aliasing can be done using the +A option but in my case it  
> takes
> enormous amount of time because the scene is really complex. The other  
> option is
> to create a super resolution image and then downsample it, but are there  
> any
> other better ways to do it?
>
> I'm totally clueless about vignetting and bayer demosaicing. Is it  
> possible with
> povray?
>
> It would be really helpful if someone can help me with generating these
> realistic looking povray images with real camera artefacts!
>
> Thanks for your patience.
>
>

MC Pov does a great job of camera noise and it renders more realistic than  
the normal Pov-Ray
http://fidos.pagesperso-orange.fr/MCPov/MCPov.html

-- 
-Nekar Xenos-

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Am 14.02.2011 09:25, schrieb Nekar Xenos:

> MC Pov does a great job of camera noise and it renders more realistic
> than the normal Pov-Ray
> http://fidos.pagesperso-orange.fr/MCPov/MCPov.html

I have to contradict you there: POV-Ray is getting the diffuse component 
wrong, as I found out when trying to use it as a reference to validate 
the radiosity code; see the thread "MCPov: Diffuse Reflection - UR Doin' 
it Wrong" in povray.unofficial.patches 
(news://news.povray.org:119/4b093e4b@news.povray.org)

I think what makes it /look/ more realistic is the blurred reflections & 
refractions instead of (Blinn-)Phong highlights.

As far as performance is concerned: I think it's really time we get a 
free-license 3.7 release out the door so someone can create & distribute 
a patch for stochastic rendering.

Post a reply to this message

On Mon, 14 Feb 2011 20:20:39 +0200, clipka <ano### [at] anonymousorg> wrote:

> Am 14.02.2011 09:25, schrieb Nekar Xenos:

> As far as performance is concerned: I think it's really time we get a  
> free-license 3.7 release out the door so someone can create & distribute  
> a patch for stochastic rendering.

..and a monte carlo patch for 3.7 with correct diffuse reflection would  
also be nice :)

-- 
-Nekar Xenos-

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Alain, Clipka and Nekar

Thanks a lot guys for your very helpful comments! I'm happy that I got a very
good response from you and I appreciate that!

Ankur

"Nekar Xenos" <nek### [at] gmailcom> wrote:
> On Mon, 14 Feb 2011 20:20:39 +0200, clipka <ano### [at] anonymousorg> wrote:
>
> > Am 14.02.2011 09:25, schrieb Nekar Xenos:
>
> > As far as performance is concerned: I think it's really time we get a
> > free-license 3.7 release out the door so someone can create & distribute
> > a patch for stochastic rendering.
>
> ..and a monte carlo patch for 3.7 with correct diffuse reflection would
> also be nice :)
>
> --
> -Nekar Xenos-

Post a reply to this message

Am 15.02.2011 10:39, schrieb Nekar Xenos:
> On Mon, 14 Feb 2011 20:20:39 +0200, clipka <ano### [at] anonymousorg> wrote:
>
>> Am 14.02.2011 09:25, schrieb Nekar Xenos:
>
>> As far as performance is concerned: I think it's really time we get a
>> free-license 3.7 release out the door so someone can create &
>> distribute a patch for stochastic rendering.
>
> ...and a monte carlo patch for 3.7 with correct diffuse reflection would
> also be nice :)

Well, unless I'm utterly mistaken and confusing terms here, monte carlo 
raytracing /is/ a variant of stochastic rendering... but yes, it would 
be nice if that patch would handle diffuse reflection properly right 
from the start :-)

Post a reply to this message

On Wed, 16 Feb 2011 05:27:37 +0200, clipka <ano### [at] anonymousorg> wrote:

> stochastic rendering

OK, I didn't know that. I googled "Stochastic rendering" and the first  
page I opened basically explained it as random dithering... ;oD


-- 
-Nekar Xenos-

"The spoon is not real"

Post a reply to this message

Am 16.02.2011 18:28, schrieb Nekar Xenos:
> On Wed, 16 Feb 2011 05:27:37 +0200, clipka <ano### [at] anonymousorg> wrote:
>
>> stochastic rendering
>
> OK, I didn't know that. I googled "Stochastic rendering" and the first
> page I opened basically explained it as random dithering... ;oD

Well, we already have dithering, so no need for /that/ (tends to look 
crappy compared to what's implemented in POV-Ray) :-)

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