POV-Ray : Newsgroups : povray.general : First unofficial patch of POV-Ray 3.7.0: UberPOV : Re: First unofficial patch of POV-Ray 3.7.0: UberPOV Server Time
16 Apr 2024 07:55:21 EDT (-0400)
  Re: First unofficial patch of POV-Ray 3.7.0: UberPOV  
From: clipka
Date: 18 Nov 2013 10:36:38
Message: <528a3406@news.povray.org>
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 

(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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