Nice work Peter.
It’s very interesting that the HDR seems to produce shadows that are both sharper *and* softer in different places than the VRaySun. Very strange! The VraySun is somewhat too sharp in certain areas and too soft in others compared to the HDR which seems more balanced.
Very interesting…
Well this is nice and all, but using an HDRI with a generic light grey material in a test scene is no good. Try cleaning a scene with full blown production materials. I’m talking about slightly glossy wall paint, silky glossiness with multiple layers for the wood on the shelves etc. You will run into all sorts of noise issues from specular highlights to reflections of glossy reflections. Rendertimes will go way up. Just saying.
I love to use HDRI lighting, even for interiors, as the subtlety of real world lighting cannot be matched by a simplified model as the vray sun and sky. But production requirements, especially for animation, make this very hard to use in some cases.
I could have done the article with full materials, but it already took me a whole day and I need to work as well 
Don’t people think it’s interesting that if you are committed to using universal settings, or brute force (as I am) that the HDR version actually rendered quicker than the Vraysun version?
The vraydomelight is just one big light really, and happens to have a sun in it. So I guess what you are seeing is less sharp shadows from the hdr sun but then there are more defined shadows from the rest of the sky, whereas the vraysky is just contributing to GI. If you look at the vraylighting element on one of the vraysun renders and compare it to the vraylighting element from a hdr sky render you can see what i mean. Correct me if i am wrong someone!
This makes sense to me. Sounds like the likely explanation. Very tempted to try out HDRs for interiors now.
my only concern would be that you will be tracing very large light (dome) through a very small window, so you may need lots of samples there. Domelight’s purpose was/is to light exteriors, approximate gi lighting (bf) at no bf costs.
Since the original poster asked specifically for HDRI lighting in interior animation, let me add some thoughts to the discussion:
The paradigm of “image quality first, render time is secondary” isn’t going to work for animation.
Most archviz shops I know of are rather small businesses with limited hardware access. For most projects, you’ve got a limited budget too.
Therefore, render time becomes a mayor issue if you have to crank out thousands of frames. Therefore, going for maximum image quality isn’t always possible.
Sure, you have to optimize your scenes. That is craftsmanship you have to learn. Read the documentation, do render tests, check out the tutorials about scene optimization, some written by the very same guys posting in this thread.
Still, sometimes - and this depends on your scene - just dialing in your subdivs doesn’t cut it. Then you have to make hard decisons and sacrifice image quality for render speed.
Precache your GI, so goodbye to Brute Force. HDRI is giving you a hard time? It may be better to store the domelight to Irradiance Map and forget about those speculars. Or get rid of the HDRI and approximate it with Vray Sun & Sky.
Do you really need all those glossy reflections everywhere? The list goes on…
It basically comes down to managing your ressources. There is no silver bullet.
I agree, however he also asked how to get the image to the next level of quality, so he is interested in taking it to the next level. I had a run at his scene. After I was done with it, it took 18 minutes on my dual 6 core xeon for final frame, grain free etc. That is quite acceptable, using hardware that’s 5 years old. So not to disagree with you, but also, there are steps to be taken and $ to be spent, if you want to keep up with the trend. Like, upgrading to vray3, will also cost you a bit.
the answer to this question is nearly always yes though…
EVERYTHING has Fresnel!
I’ve really enjoyed seeing the varying opinions in this thread, and would like to conclude that I DON’T think I’m insane to light my interiors in this way, and in answer to Crush, even for my animations.
After extensive, and extremely helpful testing by, and conversations with, Morbid and Peter, one of the main issues I am facing is down to hardware, plain and simple. It was ace to realise as an artist I’m not doing anyting particularly wrong, but I am constantly fighting against the ‘cutbacks’ alluded to by Crush in order to get reasonable render times. The key ones for me are storing the domelight in the imap and limiting glossies.
Both Peter and Morbid provided a solution that was desirable, both producing clean renders with great lighting quality and excellent render times, even with materials. Peter used HDRI as seen in his tutorial, Morbid used VraySun/Sky and Portals. When I ran both the test scenes on my setup, the render times where high and there was a touch more noise in the renders, therefore we realised our hardware is very much dated and the upgrade to Vray 3 is required!
I explored Peters setup a bit more and ran an animation with his settings, and there was too much noise to be able to present to clients, but as Peter claims he’s not interested in this side of things! So I expect if I up the light subdivs I’ll have slightly higher render times than I’m used to, but with much better lighting quality and shadow definition.
So I think with a better hardware setup I can easily achive the next level of quality I want, just need to find some pennies to pay for it!
Thanks for sharing your findings, and thanks to everyone who contributed. I don’t post much, but let me tell you guys that I value this forum immensely because of the different approaches and insights presented here for years.
Regarding the noise issue, I forgot to add that you’ll also have to keep in mind what happens afterwards. Sometimes, minor noise issues in the rendering become far more visible when there is extensive color grading applied in post.