HDR Packages - which image to use for the dome environment map?

mork

A thing that bugged for quite a while now:

When I download a HDR package somewhere, there are usually multiple images within:

* an Environment texture ("ENV", usually HDR)
* a Reflection texture ("REF", usually HDR)
* a large texture of the scene (usually JPG)
* maybe backdrops (usually JPG)
* sometimes an IBL file

Which one would be the correct one to use for the dome? They all kind of work, but then, I can put any random image in the dome and it would also work (albeit not very good).
I'd go for the ENV hdr, but then there is this thing that when I don't draw the dome, I cannot change parameters while already rendering. That's a no go on CPU. But when I use the ENV hdr, it does not actually show the scene in the background, but a blurry version of it.

So I usually go for the "large texture of the scene", but I'm not sure if that is intended and if I'll get the best results with that one. Probably not.
But if I should use either the ENV or the REF texture, how can I draw the background without it being blurry as in the ENV and REF textures? I could add a dome geometry and put the "large texture of the scene" on it, but to my experience that blocks the light rays of the IBL, right?

I'm puzzled. :)

-mork

SpottedKitty

Note that the whole point of using an HDR light is right there in the name — High Dynamic Range — which means there's a lot more lighting data than you get in a plain conventional image. A jpg isn't HDR, it just doesn't have enough data in it; you can put one into an environment light parameter slot if you want, but it won't produce a good light source.

Another gotcha is that not every HDR will make a good environment dome background — for that, you need a very, very large image, otherwise the rendered background comes out blurry and low quality; that's probably the problem you're seeing.

There's a thread here somewhere with links to an HDRI archive that releases a new freebie download every Friday; if you look at the download sizes, most of the images are available in different sizes up to 16000 pixels. If the downloaded file isn't at least a few hundred MB, it's just not big enough.

Richard Haseltine

As I recall, those would be 3Delight sets for ubEnvironment (or non-DS entirely). I think, certainly in the former case, that the ENV HDR will be blurred and the REF (designed to be used for reflections) not - for Iray I would use the REF HDR.

fastbike1

The real story is that everything on the 'Net that claims to be HDRI, ain't necessarily so or at least not for the best use with Iray within Studio.

 

kitakoredaz

because many free HDRI or Exr which we can get, were made to use, light map and background map individually,.

but iray dome do not distinguish them for iray Dome.  actually I felt same problem, when I start iray. asked in forum. 

after all, I simplly use Ref map (or plug it as Enviroment map)

which usually offered as HDR image , (can keep dynamic range )  but there is case, it is so low resolution to use as background, though it still useful as env light. 

(see daz offer default dome HDRI ^^; do we hope to use it as back ground enviroment?)

 

 

mork

Oh I think that I have a real HDRI, but as said, it's rarely a single file, no matter where I download it from (DAZ products being the exception).
For example I got a package from this page: http://hdrlabs.com/sibl/archive.html
In the file for "Mono Lake", as an example, there are these files:

Mono_Lake_B.ibl
Mono_Lake_B_Env.hdr
Mono_Lake_B_HiRes_Tmap.jpg
Mono_Lake_B_preview.jpg
Mono_Lake_B_Ref.hdr
Mono_Lake_B_Thumb.hdr

Thumb and preview is out of question, which leaves us with:

Mono_Lake_B.ibl
Mono_Lake_B_Env.hdr
Mono_Lake_B_HiRes_Tmap.jpg
Mono_Lake_B_Ref.hdr

After your replies I think the "Ref" texture is the one to go for. It still won't make a good background, but I might find a solution for this.
Thank you very much! :)

-mork

Fishtales

I use the HDRI from the sIBL site too. These are made for the sIBL system which uses all the maps in its system. For Studio, or some other programs, the maps you want are the .hdr or the hires .jpg. Each one does something different.

The Env.hdr is for lighting only and isn't used for backgrounds just for ambient light.

The Ref.hdr has the lighting information that is in the Env.hdr but is also an image that can be used as a background. Both of these can be used in the Environmental Map chanel.

The HiRes.jpg can be used either in the Dome Environment Map chanel or in Environment/Backdrop to give a background.

The Preview.jpg in the Dome or Background but is very low res and washed out.

The .ibl image isn't used in Studio as far as I know.

mork

That's very informative as well, thank you! :)