Re: Ray Length "Depth Pass" -- DOF in Reflections

Date : Mon, 14 Aug 2006 16:39:49 +0200
To : XSI(at)Softimage.COM
From : "Gent Krasniqi" <gentkr(at)gmail.com>
Subject : Re: Ray Length "Depth Pass" -- DOF in Reflections
well md_aperture gives convincing results if you use enough samples and if you're willing to accept the rendertimes.  Let's not forget that with maxwell you're looking at ~ 20 hours (on an up-to date system) for the noise to clear up on reflective surfaces such as in this case.

This is a typical scene where a renderer like Maxwell will turn out largely 'undisputed' superior renders, because it is what's it advertised to be.. a simulator.  But you'll have to pay in someway with every renderer, in maxwell's case its rendertime.

Though I think that for fields such as product visualization etc, that require highly realistic stills, it probably is the best choice.


On 8/14/06, Christian Götzinger <cg(at)pension-goetzinger.de> wrote:
Hi,

I didn't try md_aperture, but last time I checked it didn't really give
fully convincing results. I might want to give it another try, though I
think it may be too slow.

As for the reflections in the rings - I saw your image in the CGTalk
thread. If you compare that to ThomasAn's image directly above it
becomes obvious that the reflections in the two rings are not blurred
because of blurry reflections. You can clearly see out-of-focus
highlights that are caused by the depth of field. These are missing in
your 2D solution which is why your version looks flat.

Furthermore, the challenge rules state that both rings are supposed to
have "high gloss reflections" - only the main bodies of the coins are
supposed to have very blurry reflections. But as you have seen, even by
bypassing the rules and making the reflections blurry you cannot
simulate the rich look of out-of-focus highlights.


Gent Krasniqi wrote:

> Did you try md_aperture?  There is a spdl somewhere at cgtalk.  It's
> still slow (like 3d dof in 'most' renderers) but has more control like
> aperture shape etc.
> BTW, alot of the 'sparkle' in the reflection of that gold ring is
> caused by the gold ring not being perfectly reflective (alittle
> roughness) and high gloss.  Doing a render of that scene right now and
> will post a mental ray result here.



Apparently it originates from Maxwell Render. If I recall correctly
however, I've seen similar quality come out of VRay in this thread.
I don't want to majorly dwell on this particular image however, as it
was just supposed to be one example for an area where I can't seem to
get convincing results out of mental ray.

By the way, I did try X-DOF on this scene back in the day, and the
results were absolutely horrible, they screamed "post DOF".
This is especially annoying because X-DOF's Lens Shader seems to
calculate everything correctly (the reflections become way more
defocussed than the ring surfaces), however the X-DOF Output Shader -
which is supposed to wrap everything up - doesn't care about this and
incorrectly adds the final blur based on Z-depth, not on ray length.


Steven Caron wrote:

> hey christian what renderer did this image originate from? just curious...
>
> steven




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