[Sidefx-houdini-list] Camera model

Colin Doncaster colin.doncaster at gmail.com
Thu Nov 29 08:22:58 EST 2012


Why would you want to render distorted CG?  How/where is that being used in a pipeline?  In most cases you work out the lens distortion on the plate, de warp, track/roto/prep, integrate undistorted CG and elements and then rewarp.  

Maybe for an all CG render and I assume you want it to look "real" but in many cases I would argue these warp/dewarp tools are targeted at acquired plates. 

I'm not saying it's wrong, I'm just curious as to where in the pipeline is the benefit?

Cheers

On 2012-11-29, at 7:01 AM, Neil Scholes <neil at uvfilms.co.uk> wrote:

> Yes absolutely
> 
> I manged to get the precompiled binaries working in Nuke - works a treat
> 
> I wouldn't know where to start using this info for building a Houdini lens shader!!
> 
> Anyone out there who can? - well id buy you at least 2 pints.
> 
> A COP node would be cool but not _as_ cool.
> 
> 
> Neil Scholes
> 
> www.uvfilms.co.uk
> +44 (0) 7977 456 197
> 
> On 29/11/12 11:48, Frederic Servant wrote:
>> 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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>>>>>>> 
>>>>>> --
>>>>>> Un saludo
>>>>>> Best Regards
>>>>>> Pablo Giménez
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