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Am 18.11.2013 15:36, schrieb Warp:
> In povray.general clipka <ano### [at] anonymousorg> wrote:
>> The most notable change is the addition of BLURRED REFLECTIONS
>
> What are the advantages compared to the current trick (which can be
> used to achieve images like http://iki.fi/warp/pics/Rubiks_Revenge2.jpg )?
There are three drawbacks of that trick:
(1) It is well known to scale poorly in terms of render time when any
other oversampling features are involved, such as focal blur, area
lights, and most notably other objects in the scene that also have
blurred reflections.
(2) It is a mess to parameterize for physical consistency with the
highlights.
(3) It becomes an ugly hassle when working with multi-layered (or
otherwise complex) textures; this is not only an issue of ease of use,
but also of render time. (Averaging multi-layered textures that only
differ in the normals of the topmost layer is anything but effective, as
not only the reflection but each other layer is computed N-fold as well.)
I know that you love that trick, and have in some tutorial made claims
that it is a sufficient replacement for inbuilt blurred reflections, but
the above facts make it no more than a nasty kludge. One that can be
used to good effect if you invest sufficient time and effort, but a
kludge nonetheless.
While I can't claim the current UberPOV implementation of blurred
reflections to be particularly speedy, there are mechanisms in place to
limit the number of tertiary rays when combining it with focal blur,
area lights, subsurface light transport, or just a vast number of
objects with blurred reflections, so that it doesn't get too bad with
more complex scenes. There is also room to add some tweakables that may
help speed things up.
The parameterization is designed such that using the same parameters as
for the specular highlights will give physically accurate results.
(Admittedly this only holds strictly true if you don't use variable
reflection or fresnel, but that's not a problem with the reflection but
with the current limitations of highlights; some future UberPOV version
will address this as well.)
As for ease of use, it's as simple as adding a roughness parameter to
the reflection block, and activating some feature that provides for
sufficient oversampling (either focal blur, the new anti-aliasing mode,
or both).
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