HDRI interior

[Guest]

I have been doing some tests with using only a HDRI image of an exterior environment for a light source when rendering an interior room. The room is fully finished with walls, ceiling and windows. The results are very splotchy and noisey. It is as if the HDRI doesn't not produce enough light. From what I understand renderers such as Octane use a similar method where by it only uses HDRI image's for lighting and the results are much brighter and cleaner.

Perhaps I am missing a trick here but can you just use HDRI maps in V-Ray or does it still require some direct lighting such as the sun to work correctly? I can not seem to find any examples of full interiors being rendered using only HDRI images.

Thanks,

[joconnell]

Pretty much all of Peter Guthrie and Bertand benoit's work are using this as far as I know?

[Guest]

Hmm I will check them out but from memory I thought they use a combination of hdri and direct lighting for interiors. Not just hdri alone.

[Morbid Angel]

When you are using hdr, what is the hdr from? is it used as regular environment? does your walls/interior objects block the hdr from environment?

[Deflaminis]

I've tried with HDRI only with the same results. I was able to subdivide enough to get a clean render, but the render times were too high.

So I added a sun, and all the problems went away. So that got me thinking... is it the lack of any other light source causing this? So I added an ambient light (+GI on it) with a dark gray and it seemed to help very much. That was a while back, and I never did finish that project.

[Morbid Angel]

I've tried with HDRI only with the same results. I was able to subdivide enough to get a clean render, but the render times were too high.

So I added a sun, and all the problems went away. So that got me thinking... is it the lack of any other light source causing this? So I added an ambient light (+GI on it) with a dark gray and it seemed to help very much. That was a while back, and I never did finish that project.

Well if you try to illuminate the interior scene with dome light or env gi light from outside, using purely hdr, the sampling of that will be extremely difficult, hence the splotchy result and long render time to clean it up.
What would be the point of illuminating an interior with env hdr anyway? the light that comes through the windows can just be simple color, since the samples probably only hit very small areas of the hdr.

[Guest]

Thanks for the input guys. I typically use something from Peter's collection such as http://3docean.net/item/hdri-1103-su...thor=paguthrie. I would have thought that this HDRI would give enough illumination for interior with closed walls.

Ideally the sun spot that is present within the HDRI would act as an actual sun light in combination with the surrounding sky. But this doesn't seem to be the case. You still need to add a direct light source in the scene to get any decent contrast.

[Morne]

or LOWER the gamma of the hdri to something like 0.5

[Guest]

or LOWER the gamma of the hdri to something like 0.5

You could do this but it does alter your lighting. You end up in an ever frustrating spiral of fixing one issue to satisfy another.

[Deflaminis]

What would be the point of illuminating an interior with env hdr anyway?

You're totally right of course, sometimes I just do things to see if I can.

[Morbid Angel]

You're totally right of course, sometimes I just do things to see if I can.

its quite simple really, the hdr dome is so big, that the samples shot from the interior through the window really hit just single pixels of the hdr, which is why it takes so long to get anything clean out of it, there is really no reason to use it. The examples in the links above make a difference because the interior is open so a lot of illumination from hdr gets through.

[Guest]

You're totally right of course, sometimes I just do things to see if I can.

Same here for me. To be able to illuminate an interior with just a single HDRI map would be so much faster.

[theedge]

Unless you're working on a certain type of interiors that have VERY large openings you will not gain anything from using a hdri except much longer render times. Typical examples are for examples some classics like the farnsworth house or Philip Johnson's glass house.

[zeronove]

What Morbid said make perfectly sense, so which are your suggested practices to illuminate an interior scene?
Let's say as an example a common architecture (not medioeval like window size but not so extreme wide like "modern times"; do you just put vraylight planes (no portal) to the windows and a vraysun, that's it?
I've never had great success using hdri for interiors, as well, but, as someone said, after looking to Peter and Bertrand images, I was beginning to think that I was doing something wrong.

[suurland]

Make sure the HDRI is loaded as a texture in a Vray Domelight.. that eliminates a lot of splotches compared to just having the hdri in the env slot.

/Thomas