The CPU side of Cycles has actually seen some nice optimizations over the past year (optimization commits that only applied to CPU rendering).
More optimizations are still to come (and is a major focus for Cycles this year), don’t expect to soon render complex interiors on the CPU in minutes though.
marcoG_ita, thanks for the update, i’ll give it a try later - I love that Evermotion scene.
I’m totally with you Sunburn, you get what I’m talking about.
Hi, if you look at the Luxrender development for the last months there happen a lot.
You can use all devices, even Intel GPU mixed with Nvidia GPU and so forth.
There are some render algos like BiDir Path, Metropolis LT, Adaptive Render, Intel Embree Integration, new tile repository code (solve the last tile problem) and more.
If you know what you do Luxrender is not slower than Cyles.
Octane is a really advanced GPU engine, one or two jobs and the Software is payed.
Some companys spend 10000$ for one render node, they don´t care about 500$.
Nothing for the hobbyist world. 
Cheers, mib
By reading the forum Lux has made giant steps in last months, though it seriously lacks of usability IMHO, only developers and deeply involved users seems to be able to test it, i mean…if a render engine is good, easy to use/integrate and free, you would see lots of gallery entries or at least lot of tests and interest around, which isn’t the case now because as I said, it’s damn hard to give it a go.
I’d love to test the new biasPath PT, but haven’t been able honestly…which build, which Blender version works, which Luxblend, missing .dll when trying to setup everything… 
The problem with Cycles is it does needs more tweaking to get better interiors than other biased solution. Interpolated GI (Vray, Corona, Redshift…) does a great job with smooth GI bleeding everywhere, filling every corner in a reasonable amount of time compared to pure brute force approach…so in my experience this so called “nasty” bias, comes in handy for these scenarios, giving superior results with less efforts.
Another problem is the tonemapping as already said…a whole topic on that here in the forum, Lukas made a great patch about it which unfortunately isn’t going to hit master until reworked through OCIO, from what i can understand…
Other one is Fresnel doing something off, giving an odd CG look with dark edges and dull facing highlights…hoping for devs attention if any, maybe in the future (coated materials are the vast majority in archviz)
However Cycles, by investing time and efforts to study it (as any other software), is capable of getting really near to those other engines mentioned previously, and plus it has ALL the benefits of pure Blender integration, viewport preview, unlimited flexibility with its node system, straight compositing right after rendering is finished, and many more…i don’t say it’s perfect nor completely “finished”, but it’s much more capable than other ones around which are not even open source and free.
@Jay-artist: I took the liberty to tweak and give a test to your room scene to resemble more a typical interior light setup we’re aiming for. Lots of stuff can be improved but i had limited time.
Light sources are exactly the same (though the sun was blocked by windows emitters, you need to uncheck shadow rays for the emitter planes).
Original
Tweaked - 30 minutes on CPU
Hi, marcoG_ita, may you start with 1.4 RC3 and the included exporter for Blender 2.73.
http://www.luxrender.net/forum/viewtopic.php?f=12&t=11446
The Lux guys are also very nice and try to help you to get it running on forum or #luxrender.
Cheers, mib
Thanks marcoG_ita, It’s a little too bright, but an improvement in character overall.
Since I first uploaded “The White Room” (the scene above) on Blendswap back in April 2012 I’ve obviously learnt a lot - least I hope I have! The shadows being left on with the mesh emitters was an obvious error on my part, nobody had pointed it out sadly so I never fixed it – but silly me either way.
What isn’t apparent was that I’d edited it in post to boost the render - obviously hard to upload to blendswap - sounds like I’m making excuses, I’ve my reputation to think of! 
I agree you can do a lot more tweaking in Cycles - my wife would say I’ve spent too much time tweaking Cycles O_o
Sometimes you just want to get a good result without all the messing around and get something realistic. But it’s still that Path tracing thing in the end.
I also think because Cycles is so versatile (well done devs), it doesn’t really shine in one place specifically yet, but with those improvements you mentioned and possibly other rendering methods, it would probably be a killer engine. Although we all know, its still the best for free.
But have you tried render an interior at night time in Cycles with a lamp in the corner, forget it!
On Luxrender, I’ve always liked the renders, but wondered how the hell you get a finished render that doesn’t take several days or more. Although I’m rusty on it now, I know several years ago, probably like many users I spent a lot of time learning it and tweaking it. I really hope it does improve and become significantly faster!
by the way how would you make cycles lamp emission strength go to power based numbers ?
in maxwell you can set the power of the emission to lumens
there is a blackbody node but I don’t know about a phisical power node… is there a node for this or can it be created ?
I know that it isn’t accurate in cycles but just for good aproximation measures maybe there is a solution somewhere
Light power is expressed as Watts internally. As for how they’re exposed to the user… your guess is as good as mine.
Just a remark from the “technical” side:
Often, people write stuff like “Path tracing can’t archieve photorealistic / physically correct results”. That’s just wrong: For research, PT is commonly used as a reference as it’s essentially the gold standard in correctness. Now, of course there are many things that PT is bad at (caustics, heavy occlusion etc.), but in theory you can render everything by throwing enough samples at it.
From an artistic point of view, the bias (=structural error, as opposed to noise) of many other methods might look better and suit the scene more, and that’s perfectly fine. However, that doesn’t make it “physically correct”.
The points that have been mentioned here (incorrect Fresnel, tonemapping, spectral rendering etc.) actually are independent of the integrator used, if Cycles had a full-blown BiDir MLT or VCM integrator (the really cool stuff), these issues would still be there.
no we cry because Cycles is not Maxwell with the rendertimes of V-Ray
Is it true that V-Ray can do light cache on the GPU in version 3 ?
This thread is very interesting. I also do Archviz and love Cycles, like Jay-Artist. And like Jay-Artist and Sunburn I think Cycles could be a good alternative in Archviz.
I know that Archviz is not the focus of Cycles but there are things missing that could bring Cycles to a bigger audience.
What I really miss is a real physical camera, eye balling a real camera is dificult. And why not a correct fresnel or a option to have one?
I have Thea and I really like it but I really like the idea of all open-source workflow. The latest development of Lux seems really good and will be the alternative for Archviz. From what I tested the speed issue is being resolved in the new Luxcore.
marcoG_ita
However Cycles, by investing time and efforts to study it (as any other software), is capable of getting really near to those other engines mentioned previously, and plus it has ALL the benefits of pure Blender integration, viewport preview, unlimited flexibility with its node system, straight compositing right after rendering is finished, and many more…i don’t say it’s perfect nor completely “finished”, but it’s much more capable than other ones around which are not even open source and free.
Tottaly agree.:yes:
Couldn’t some of the holes or weaknesses with included shaders and function nodes in Cycles be plugged with OSL? (the Fresnel thing seems like a good candidate perhaps?)
A bit of a pain for us non-technical types that just want to plug in our real world values in a ready-made node, but it seems like somebody with the knowhow could write the script that’s needed and make it available for copy-pasta. Then you’d just plug in the value nodes needed going into it, and it should be ready to go.
Some of the spectral stuff can also be cheated to a minor extent by RGB channel separation relating to different color light within materials and using curves for mixing. Slow as hell in Cycles (obviously pushing it in a way it’s not intended to work), and not exactly 100% technically correct (more nuance to light behavior than just the RGB components), but it gets fairly close in resembling stuff like iridescence or caustic dispersion and it’s better than nothing.
I understand the wanting for a direct 1:1 plug n’ chug (damn convenient), but sometimes if you know how to “cheat” you can still get a bit more out of your render engine. Not just Cycles, having that kind of understanding and experience applies to any of 'em.
If anything bugs me in Cycles, it’s probably the volumetrics. Once you have that going on in scene space at a level that’s noticeable, the lighting values seem to go all to hell. (Want something like a hazy/dusty room, and light has to be turned up by at least a factor of 10 if not 100.) The absorption in glass by default seems a bit too high too, never looks right without a transparent mix and light path node unless you want a heavy tinted look.
I’m laughing at Cycles
THIS!!! You’ve made my day Sir. Actually I’m working on a night interior scene with a lot of small sharp spotlights, so not much help now 
But for a daylight scene this is amazing. Thanks, and great thread by the way, really informative.
Many archivist people use path tracers for interiors (octane is afaik also path-tracer). With the GPU it’s not actually that slow and you don’t need to tweak many setting like for example with photon mapping. It produces some noise, but the plus side is that there are no other strange artifacts.
Post deleted (referenced edited-out post).
Ovnuniarchos, the post is gone now.
Sunburn, how is VRay cheaper than Thea? From what I know it is:
Thea seems the best to me. Unfortunately everything is expensive to me 
On the side note, does anybody know about Indigo RT? It is a slimmed down version of Indigo that does not have shadow catchers, SSS, orthographic cameras and some other stuff. Here is the link.How useful would it be to a general freelancer? For characters it would be certainly horrible(no SSS) but seems pretty good.
Arion for the stand-alone cannot support animations(unless you export each frame individually), and the integrations are very expensive.
Maxwell is expensive. Nuff said.
Surprisingly, there are a lot of medium-price renderers out there. I remember seeing price lists at over 1000 dollars for one. Or maybe I am just crazy.
Well, I guess it is a lot easier to get your hands on a renderer now than 6 months ago.