[Sidefx-houdini-list] Camera model

Pablo Giménez pablogipi at gmail.com
Wed Nov 28 12:32:48 EST 2012


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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