[Sidefx-houdini-list] Camera model

Frederic Servant frederic.servant at gmail.com
Thu Nov 29 06:48:18 EST 2012


Hi,

3DE's Lens Distortion Plugin Kit (
http://www.3dequalizer.com/index.php#?site=tech_docs&id=110216_01) is free
to download and use.

Science-D-Visions recently started to make available a lens database to
feed it  http://www.3dequalizer.com/index.php#?site=tech_docs&id=120930_01,
of course you can feed it your own 3DE distortion parameters.

Besides Weta's Nuke plugin (
https://github.com/wetadigital/lensDistortion_3de), some 3DE distortion
lens shaders have been done for other renderers (mentalray:
https://bitbucket.org/lamaison/lmwarpdistort/wiki/Home  and Arnold:
http://s3aws.obliquefx.com/public/shaders/Obq_UVRemapLensDistortion_v204.html
).

With all those examples, it should be easy enough to do a distort/undistort
cop node or a lens shader for mantra.
--
Fred


On Thu, Nov 29, 2012 at 10:29 AM, Neil Scholes <neil at uvfilms.co.uk> wrote:

> Yeah I like
>
> in nuke you can use a plugin to match the lens distortion generated by
> 3DEqualiser - which is great because it has an excellent series of ways to
> model the lens of a whole range of different cameras - far better than
> Nukes own lens distortion node
>
> Specifically the Anamorphic Model - it rocks and is really complex
>
> I don't have the tech to build into Houdini - but there must be a way  -
> importing lens models from all the different 3D trackers out there, and
> applying before you render.
>
> Obviously you may not want to do this on a project - but i'd love to.
>
>
>
>
> Neil Scholes
>
> www.uvfilms.co.uk
> +44 (0) 7977 456 197
>
> On 29/11/12 09:02, Javier Meroño wrote:
>
>> what about a solution like this but for real?
>>
>> http://www.itsartmag.com/**reviews/Lightwave9/**realcameralens.jpg<http://www.itsartmag.com/reviews/Lightwave9/realcameralens.jpg>
>>
>> with "for real", I mean that Lightwave (yup, that´s a Lightwave screen
>> grab) lens only takes into account lens distortion and fakes the amount of
>> light entering the lens with a "pin" lens effect but it´s not really
>> changing it based on ISO or lens shutter. It wouldn´t make much sense since
>> Lightwave´s renderer ain´t physically based right now.
>> This being said, the amount of different camera lenses modelled into
>> their camera shader is staggering. It´s useful if only for the lens
>> distortion.
>>
>> If we could have a similar panel with real camera behaviour we would be
>> able to choose our "starting point".
>>
>> regards,
>>
>> Javier Meroño
>>
>>
>>
>>
>>  From: jordibares at gmail.com
>>> Date: Wed, 28 Nov 2012 17:59:43 +0000
>>> To: sidefx-houdini-list at sidefx.com
>>> Subject: Re: [Sidefx-houdini-list] Camera model
>>>
>>> Agreed, it is not that this particular approach is a silver bullet, just
>>> trying to revisit every single part of the process.
>>>
>>> :-)
>>>
>>> jb
>>>
>>> On 28 Nov 2012, at 17:32, Pablo Giménez <pablogipi at gmail.com> wrote:
>>>
>>>  2012/11/28 Jordi Bares Dominguez <jordibares at gmail.com>
>>>>
>>>>  On 28 Nov 2012, at 11:35, Pablo Giménez <pablogipi at gmail.com> wrote:
>>>>>
>>>>>  2012/11/28 Neil Scholes <neil at uvfilms.co.uk>
>>>>>>
>>>>>>  I would certainly love having a lens shader where you can import lens
>>>>>>> distortion models from apps like 3DEqualiser etc.
>>>>>>>
>>>>>>> rather than having to render larger resolutions than needed and
>>>>>>>
>>>>>> distorting
>>>>>
>>>>>> in nuke.
>>>>>>>
>>>>>>>  Well, this is  debatable.
>>>>>> If you "bake" the lens distortion in the render then you are forced to
>>>>>> rerender in case for  soem reason this lens dostortion option changes
>>>>>> in
>>>>>> the future, or changes for some shots.
>>>>>>
>>>>> True, but the whole process is simplified as you don't need to deal
>>>>> with
>>>>> various sets of transformations on various points in the pipeline…
>>>>> this may
>>>>> be debatable, true, but I rather keep it simple and re-render when that
>>>>> happens which is not that common in my experience.
>>>>>
>>>>>  And this happens sometimes.
>>>>>> Whereas rendering some extra pixels is always a good thing,
>>>>>>
>>>>> I do not agree with that, I think that is a waste of rendering for
>>>>> every
>>>>> single pass of every single shot and you count the extra hours you
>>>>> probably
>>>>> would be horrified about it as I am.
>>>>>
>>>>>  Well, it depends on the scenario, for film, rendering 10% more pixels
>>>> usually is not a big deal.
>>>> But it is quite common to have shots that are really hard to render an
>>>> due
>>>> to changes in how it is going to be composited they needs to be rendered
>>>> again and this cost more time/resources that rendering 10% more pixels
>>>> in a
>>>> bunch of shots.
>>>> As always it depends on the scenario, being able to make the same thing
>>>> in
>>>> both render and comp is always good and welcome, so I don't have nothing
>>>> against having a better camera model, just the opposite.
>>>> Doing everything at the render stage is not always the best option, same
>>>> thing goes about trying to "fake" as most as possible in comp.
>>>> So a compromise between them depending on the situation is usually the
>>>> best
>>>> option.
>>>>
>>>>  just an
>>>>>> overscan 1.1 will  allow you to add lens distortion in comp and also
>>>>>> be
>>>>>> sure that further comp manipulations like camera shakes will have
>>>>>> enough
>>>>>> pixels to work with.
>>>>>>
>>>>> I would rather have 3D camera shakes if possible… sometimes this may
>>>>> not
>>>>> be feasible for many reasons but...
>>>>>
>>>>> jb
>>>>>
>>>>>  I think it is better to render a bunch of extra pixels as a rule
>>>>>> rather
>>>>>> than be forced to rerender a expensive render.
>>>>>>
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Neil Scholes
>>>>>>>
>>>>>>> +44(0) 7977 456 197
>>>>>>> www.uvfilms.co.uk
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 28 Nov 2012, at 10:17, Jordi Bares Dominguez wrote:
>>>>>>>
>>>>>>>  The moment you enter into physically base rendering you will end up
>>>>>>>>
>>>>>>> wanting to use physically correct shaders and that ultimately will
>>>>>>> take
>>>>>>>
>>>>>> you
>>>>>
>>>>>> to realise that is actually not that useful unless you get it all
>>>>>>> right
>>>>>>> (physically correct camera and lights too) and also HDR balanced
>>>>>>>
>>>>>> properly
>>>>>
>>>>>> (no grading)
>>>>>>>
>>>>>>>> The cascade effect is huge and adapting to the approach is not easy
>>>>>>>>
>>>>>>> plus
>>>>>
>>>>>> takes longer to render each frame but in my experience is more than
>>>>>>> acceptable for the things you gain.
>>>>>>>
>>>>>>>> Ultimately, like apple did when they designed the iPad, one single
>>>>>>>> rule
>>>>>>>>
>>>>>>> forced a ton of changes everywhere (no pen, just your finger), with
>>>>>>> PBR
>>>>>>>
>>>>>> is
>>>>>
>>>>>> the same and certain render engines are already there or thereabouts,
>>>>>>> specially Maxwell, Vray and Mental Ray alongside all the other
>>>>>>> flavours
>>>>>>> inspired by these.
>>>>>>>
>>>>>>>> I really hope after this exchange of ideas SideFX see the value and
>>>>>>>> put
>>>>>>>>
>>>>>>> together a physically correct ecosystem of tools for modern
>>>>>>> rendering.
>>>>>>>
>>>>>>>> my 2 cents
>>>>>>>> jb
>>>>>>>>
>>>>>>>>
>>>>>>>> On 28 Nov 2012, at 10:04, Neil Scholes <neil at uvfilms.co.uk> wrote:
>>>>>>>>
>>>>>>>>  Interesting thoughts
>>>>>>>>>
>>>>>>>>> I was thinking that rendering linear light values in high dynamic
>>>>>>>>>
>>>>>>>> range
>>>>>
>>>>>> is the real benefit  we already have, because after that all real
>>>>>>> camera
>>>>>>> limitations such as abberation grain and iso can be faked in a more
>>>>>>> painterly way in the comp which is surely quicker and easier ?
>>>>>>>
>>>>>>>> Also the issues of real world lenses and ISO etc well each camera,
>>>>>>>>>
>>>>>>>> lens
>>>>>
>>>>>> is going to vary in accuracy even if the camera manufacturers offer a
>>>>>>> template - rather like f stop vs T stop.
>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Neil Scholes
>>>>>>>>>
>>>>>>>>> +44(0) 7977 456 197
>>>>>>>>> www.uvfilms.co.uk
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 28 Nov 2012, at 08:50, Jordi Bares wrote:
>>>>>>>>>
>>>>>>>>>  I would love that, including the camera transform matrix please.
>>>>>>>>>>
>>>>>>>>>> Jb
>>>>>>>>>>
>>>>>>>>>> Sent from my iPhone
>>>>>>>>>>
>>>>>>>>>> On 28 Nov 2012, at 00:32, Colin Doncaster <
>>>>>>>>>> colin.doncaster at gmail.com
>>>>>>>>>>
>>>>>>>>> wrote:
>>>>>>>
>>>>>>>>  Sure!  I would assume it would be helpful if all of the camera
>>>>>>>>>>>
>>>>>>>>>> parameters ended up in metadata stored in the output image - this
>>>>>>> fits
>>>>>>>
>>>>>> well
>>>>>
>>>>>> into the EXR camera info as it's meant to represent what exposure the
>>>>>>>
>>>>>> data
>>>>>
>>>>>> represents with a good reference point from where to adjust it.
>>>>>>>
>>>>>>>>  This would make a nice COP and/or MPlay addition where you can
>>>>>>>>>>>
>>>>>>>>>> quickly adjust the values and round robin them back to the scene
>>>>>>> camera.
>>>>>>>
>>>>>>>>  Cheers
>>>>>>>>>>>
>>>>>>>>>>> On 2012-11-27, at 6:17 PM, Jordi Bares Dominguez <
>>>>>>>>>>>
>>>>>>>>>> jordibares at gmail.com> wrote:
>>>>>>>
>>>>>>>>  I don't imagine anyone aspiring to get noise simulation baked in
>>>>>>>>>>>>
>>>>>>>>>>> their render and with the ever expanding electronic cameras
>>>>>>>
>>>>>> configurations
>>>>>
>>>>>> and codecs this simply may be impossible but it may be useful to get a
>>>>>>> metric for density of noise in the picture that we can feed into the
>>>>>>>
>>>>>> comp.
>>>>>
>>>>>>  hope it makes sense
>>>>>>>>>>>> jb
>>>>>>>>>>>>
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>>>>>>
>>>>>> --
>>>>>> Un saludo
>>>>>> Best Regards
>>>>>> Pablo Giménez
>>>>>> ______________________________**_________________
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>>>>>>
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>>>>>
>>>>>
>>>>
>>>> --
>>>> Un saludo
>>>> Best Regards
>>>> Pablo Giménez
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