Severi Salminen wrote:

> See the indigo site gallery. Some captions include render time. Of
> course that tells you nothing about how good/bad the image looked in
> less time. Remember that with brute force you see a lot even after 1 minute.

I looked. I remember that gallery. 18 hours on one of the archetecture. 
Essentially set it, then come back the next day, and you might have a 
nice image. :)


I dunno, These types of renderers do have some interesting applications, 
I could see an architect using them to do a true physical light 
simulation on a building design, using various lighting schemes/time of 
day, etc.. But for creating "photorealistic" rendered images, my bets 
are still on raytracers, they're not a physically accurate simulation, 
but they do a decent approximation.

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Severi Salminen a écrit :
> Mike Raiford wrote:
> 
>> You didn't answer his question. I'm also curious about render times, but
>> you completely dodged the question.
> 
> See the indigo site gallery. Some captions include render time. Of
> course that tells you nothing about how good/bad the image looked in
> less time. Remember that with brute force you see a lot even after 1 minute.

Maybe in the case of these renderers some other indicator of rendering 
time should be used. Technically you can let them run forever, the image 
is never finished, and getting better all the time...

The curve of "noisiness" vs. rendering time would be interesting. For 
some definition of "noisiness" :-)

I'm attracted by the idea of these unbiased renderers because of the 
ease of use described in another post. What holds me back is indeed the 
scene description language. And laziness ;-)

-- 
Vincent

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Warp wrote:

> Am I incorrect if I get the impression that these unbiased renderers
> offer nothing else than unbiased rendering? 

"Nothing else than perfect simulation of light". Nope, nothing else ;-)

> In other words, even the simplest of scenes will take hours to look
> ungrainy, no matter what you do?

Define "ungrainy". But yes, it is a tradeoff. You get grain, but you get
the same results no matter what features there are in the scene.
Caustics don't cost extra. Global illumination doesn't cost extra. Etc.
I can make a similar question:

With PovRay you don't see even one single renderd line with "perfect
radiosity/photon mapping/area light size, anti aliasing etc. It is a
trade-off, again.

Also, there are many ways to speed up brute force renderes. And there
are many ways to do it. Like path tracing, bidirectional path tracing
etc. You can implement various methods that reduces the amount of rays
needed for certain variance. I have yet to research those more.

>   Sometimes I use POV-Ray to get simple 3D-looking graphics for diverse
> things. The big advantage is that I can do it easily and POV-Ray renders
> it very fast. We are talking about a few seconds even for large-sized
> images. It would be completely counter-productive to have to wait for
> hours for a simple image to look non-grainy, when all you want is something
> quick which looks "cool" and "3D'ish".

I do the same thing now with my own program. I get a grainy preview
pretty quickly. And the grainy preview show perfect features. If you
simply want "3D-looking graphics" there are many a lot faster and better
options than PovRay. You discard the realism but you get it fast. I'm
more interested in photorealism.

>   For this reason even if POV-Ray in the future supports unbiased rendering,
> it should always be an *alternative* method of rendering, not the only
> available one. Removing the current phongshading-based rendering would be
> a setback in many areas. After all, POV-Ray is not *always* used for
> physical simulations of reality.

I agree that there are situations where you need speed over accuracy.
That is true. But also the opposite is true. After all, POV was created
to create realistic images - not the give decent results as fast as
possible. I'm not sure what is the general opinion: do users want to get
the best possible results in longer time - or okayish results in less time?

I belong to the first group.

I attached a very simple scene that took 10minutes to render to this
noise level. You can see caustics where reflective sphere and ground
meets. This is a simple scene where POV would be a lot faster (if you
know how to set it up properly..) Im also sure that good brute force
renderers give a lot better results in shorter time than my immature
renderer. The second image was done in 50 seconds. Just to show the
difference.

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Attachments:
Download 'kuva5.jpg' (20 KB) Download 'kuva6.jpg' (45 KB)

Preview of image 'kuva5.jpg'

Preview of image 'kuva6.jpg'

Mike Raiford wrote:

> I looked. I remember that gallery. 18 hours on one of the archetecture.
> Essentially set it, then come back the next day, and you might have a
> nice image. :)

Actually, you'll have a good image in less than 1 hour. After 18h it is
very good :=)

> I could see an architect using them to do a true physical light
> simulation on a building design, using various lighting schemes/time of
> day, etc.. But for creating "photorealistic" rendered images, my bets
> are still on raytracers, they're not a physically accurate simulation,
> but they do a decent approximation.

What do you mean "your bets are on"? Brute forcers give always better
looking results. Nobody can claim anything else. The only problem is the
time it takes to get to decent noise levels. So other than speed my bet
on photorealistic images are, of course, on brute-forcers. And we know
how the situation looks after few years of multi-core CPU development :)

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Severi Salminen <sev### [at] notthissaunalahtifiinvalid> wrote:
> I do the same thing now with my own program. I get a grainy preview
> pretty quickly. And the grainy preview show perfect features. If you
> simply want "3D-looking graphics" there are many a lot faster and better
> options than PovRay.

  How many of them are for Linux? Of those, how many of them work without
OpenGL?

  And if something takes 5 second to render instead of 1, big deal.

> You discard the realism but you get it fast. I'm
> more interested in photorealism.

  A 3D button for a webpage doesn't need any more photorealism than what
POV-Ray can offer in a 1 second render.

-- 
                                                          - Warp

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Severi Salminen wrote:

> What do you mean "your bets are on"? Brute forcers give always better
> looking results. Nobody can claim anything else.

False.

Brute-force rendering may generate more *physically correct* renderings 
- but that does not necessarily correlate with "better looking" results. 
Anybody who's been doing 3D graphics for more than a few days will 
quickly figure that one out. ;-)

(E.g., how many Planet Earth renders have grossly exaggerated atmosphere 
glow because it looks nicer than the physically correct version?)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Warp wrote:
>>  If you
>> simply want "3D-looking graphics" there are many a lot faster and better
>> options than PovRay.
> 
>   How many of them are for Linux? Of those, how many of them work without
> OpenGL?
> 
>   And if something takes 5 second to render instead of 1, big deal.

Blender? Maybe it requires OpenGL. But what is the problem with OpenGL?
And for web page buttos, GIMP might also be a good candidate.

>> You discard the realism but you get it fast. I'm
>> more interested in photorealism.
> 
>   A 3D button for a webpage doesn't need any more photorealism than what
> POV-Ray can offer in a 1 second render.

Ok, got me on that one :) Yes, rendering web page buttons with brute
force renderer is like killing a mosquito with a nuke. I don't know how
common it is to use POV for creating web page buttons, though...


Care to show what kind of buttons you mean?

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Severi Salminen wrote:

> Ok, got me on that one :) Yes, rendering web page buttons with brute
> force renderer is like killing a mosquito with a nuke. I don't know how
> common it is to use POV for creating web page buttons, though...

I've certainly come across people trying to do this more than a few 
times. [POV-Ray makes it so easy. It's so scriptable...]

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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I've seen some amazing renders of both Indigo and Luxrender (the main 
developer of Lux was an Indigo developer, or so I heard) with 
rendertimes ranging from 10 to 20 hours.  Both interiors and exteriors. 
  Of course, the specs of such machines are well above the current 
desktop standard -- I'm guessing they run in quad-cores from specialized 
architectural firms and the like.

Of course pov-ray and other renderers employing finite-step approaches 
to GI -- radiosity and photon mapping -- also render much faster in such 
machines.

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Invisible wrote:

> Brute-force rendering may generate more *physically correct* renderings
> - but that does not necessarily correlate with "better looking" results.
> Anybody who's been doing 3D graphics for more than a few days will
> quickly figure that one out. ;-)

You are correct: I was really talking about photorealistim. But I don't
think brute-force means you couldn't exaggerate things or create
effects. It just means that the results are more accurate looking. Of
course, if you want to have a large area light which casts sharp
shadows...or transparent objects that create full shadows. :) I wouldn't
consider that a big loss.

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