[Sidefx-houdini-list] Camera model

Javier Meroño javiermerono at hotmail.com
Thu Nov 29 04:02:32 EST 2012


what about a solution like this but for real?

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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> >>>>>>> 
> >>>>>> 
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> >>>> 
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> >>> 
> >>> 
> >>> 
> >>> --
> >>> Un saludo
> >>> Best Regards
> >>> Pablo Giménez
> >>> _______________________________________________
> >>> Sidefx-houdini-list mailing list
> >>> Sidefx-houdini-list at sidefx.com
> >>> https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
> >> 
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> >> 
> > 
> > 
> > 
> > -- 
> > Un saludo
> > Best Regards
> > Pablo Giménez
> > _______________________________________________
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> > https://lists.sidefx.com:443/mailman/listinfo/sidefx-houdini-list
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