[messire]

Hello,

A few hours available for finally trying myself at HDR skies in SU/MR!
I've finally got myself to understand the settings for the first scale settings so the ground does not show, and how to rotate the sky using the offset settings so the sun position matches that of the 3D real north or time settings.

Now my problem is to be able to cast shadows using the HDR.
I have read somewhere that by reducing the gamma of the HDR to 0.75 you can get them to cast shadow but image is dark despite intensity set to 9.

I would like to know how you guys do it!? Should I use the illumination map too?

Question 2: Is it possible to use physical sky/Sun AND have a HDR image at the same time?

Thnx!
Nils

[messire]

Gosh found a partial answer:

You can set the sun in illumination channel while having a HDR in background!
Seems to work!

Still would like to hear on how you do it!
In what case is illumination / refraction channels usefull?

thnx
Nils

[JDHill]

Basically, you will only get sharp shadows from an HDRI alone, if it is a high quality HDRI, which actually contains pixels with intensity far outside the visible range. If you were to take a jpeg and convert it to HDRI, it would still only contain the dynamic range of the source jpeg (i.e. min=0, max=255), such that a white pixel on the sun can only have the same value as any other white pixel. On the other hand, in a high-quality HDRI, a white pixel on an object would have a value corresponding to the jpeg's maximum of 255, and a white pixel on the sun a much higher value of, say, on the order of 30,000. It is because the sun pixel can have such a high relative value that the HDRI is able to cast shadows, and that's what is meant by saying that an HDRI would be a high-quality one.

When your HDRI is not of high-quality, there are a couple of options; basically, either a) open it in an HDRI editor and manually paint the high-intensity regions to actually have high intensity, or b) use it as-is in the background/reflection/refraction channels, switch the illumination channel to use active sky, and manually line up the sun direction with that depicted in the HDRI.

[messire]

Thnx JD...I found that by trial and error too...took me a while!
Got myself a HDRI from Peter Guthrie..they are really nice and extremely efficient
I still have problems ( maybe I should get other ones too...because HDRI's are way less easier to use than sun to cast shadow...usually you set a time during the day for example in june / 11 am...It seems most of the HDRI I saw are having the sun set pretty low in the sky...it means they can be used for morning scenes or later in the day..It means if you want to be able to use HDRi and still be able to choose any time of the day, you need to have many different Skies with different sun altitude..

N