[fulkrum]

Hi guys.
Regarding the use of HDR and illumination I have a big doubt... Where are the shadows casting by the sun in an HDR image used for lighting and background?
I use to set a light studio type HDR for rendering products and I always have what I want but lately I have been rendering some exterior architectural views and I'm using panoramic sky HDR for exterior lighting but these do not cast shadows! And the illumination is to dark so I need to set the intensity up to 8 or 10 in the illumination chanel so that the sceene looks clear. Am I doing something wrong?
I have tryied different HDR files, the samples included in the Maxwell suite and another of the "radiant skies" series and I just don't get realistic shadows in my models. What is happening? What am I doing wrong?

Thanks.

[JDHill]

To cast shadows, you need to use a high-quality HDRI, the pixel values of which actually describe a realistically-wide range. Consider viewing an HDR image on your 0-255 RGB monitor; if we describe 0-255 using the range 0-1, the value of the sun disc area in a good HDRI might be on the order of 30K. That's why a good HDRI casts shadows, and why a mediocre one never can.

There's a trick you can use, though, with Maxwell. Set up a simple scene (in Rhino) using your desired HDRI and export to Studio. In Studio, go to the Environment panel and set the IBL Illumination channel to Active Sky. Then, enable the sun and adjust the date/time such that it lines up with the sun, as shot in the HDRI. Once you have that, use Environment > Sky Settings > Save > As HDR. Back in Rhino, load this new HDRI and render in Fire. You will probably find that you need to go back to Studio, adjust your camera, re-export the HDRI, and then go back to Rhino and re-export the scene to Fire (in order to re-load the HDRI) a few times before you get the ratio right. When you're done, you'll have an HDRI that you can use later on without any fuss. Note that this will only work with HDRIs in which the sun is the only really out-of-range light source; when that's not the case, other light sources in the HDRI will be too dark, as compared to what they would have been had the HDRI been of better quality in the first place.

[fulkrum]

I have been doing some triks to cast shadows but this is very disapointing... I never expected that the Radiant Skies by Dosch were so mediocre... I thought Dosch was a good option but is good to know they're not before to waste money in other of their products...

What kind of HDR product could you recommend? I'm looking for one set with nice skies with differents effects (noon, night, day, cloudy, sunser, etc.) that gives a correct lighting value -included shadows-.

This "radiant skies" maps seamed to have a respetable resolution...

Thank you for your advices.

[JDHill]

Sorry, but I am not knowledgeable on who provides suitable HDRIs -- you might want to read, and/or post your question, in this thread in the main Maxwell Render forum.

[bograt]

Look up cg-source.com,
There are some good hdri and they are fairly cheap, don't trust dosch. http://www.cg-source.com/details_hdrisk ... pricat=sky
All of the hdri files are quite good and cheap.
A good way of checking an hdri is to open in photoshop and adjust the exposure way down, hopefully you will have a good portion of the slider in which everything is back apart from the sun.
You can always edit them manually and dodge in the sun to the correct exposure but it is always good to start with a good Hdri... Get a Cg-source sky hdri...
Also check out these free ones: http://www.hdrlabs.com/sibl/archive.html

[AlexP]

HDRIs with sun will make render slower and will not give transparent shadows from glass.