HDRI Formats

[CJI]

Ok I've used HDRI before and had no problems. All of a sudden i can't think for the life of me how to use these HDRIs i have. They are cross cube format some vertical some horizontal. How do i map these properly in the environment slot or a dome or something? Anyone have any ideas?

 

Thanks

[ivanjay]

I know this isnt the question for this thread but why we are on the subject of HDRI's is there a benefit to using them in an interior scene? I have never used a HDRI and really am not familiar with the benefits.

[Tommy L]

Ok I've used HDRI before and had no problems. All of a sudden i can't think for the life of me how to use these HDRIs i have. They are cross cube format some vertical some horizontal. How do i map these properly in the environment slot or a dome or something? Anyone have any ideas?

 

Thanks

 

Bring in the map to the mat editor, then change mapping mode to environment. Then chose spherical mapping. Then drag into relevant slot (environment override or whatever) and choose instance. Then use the texture controls in the material editor to refine the positioning and output of the HDRI.

[Stephen Thomas]

If you're using Vray's HDRI map then you can use either vertical cross (cubic option), latitude/longitude (spherical option), angular map or light probe (mirrored ball option).

 

Any HDRIs you have in other formats can be converted using HDR Shop's panoramic transformation tool. If you're not using Vray you can also use this to convert all your maps to the latitude/longitude format for import using the standard bitmap loader.

 

http://www.hdrshop.com/

[CJI]

Thanks for the replys guys. Unfortunately I don't use Vray so no HDRI Loader for me. And as far as i know MR doesn't have an equivelant so conversion seems the option as max has nothing that can map a cross cube HDRI appropriately. I'll give HDRshop a bash. Cheers

[CJI]

Great, it took a little faffing as HDR shop 1.0 doesn't seem to have horizontal cubic mapping in the transformation source list.

 

I ended up rotating the map 90 degrees, then transforming it to a mirror ball, Rotating the mirror ball 270 degrees to get back to the right alignment, then transforming again to Log/lat.

 

It seems to have worked quite nicely apart from when i do the first conversion i get a small black seam line on a portion of the mirror ball. I'm guessing this down to sampling so im going to bump that up a bit to see if it gets rid.

 

Thanks Again, i have some useable HDRIs now.

[DanGrover]

I know this isnt the question for this thread but why we are on the subject of HDRI's is there a benefit to using them in an interior scene? I have never used a HDRI and really am not familiar with the benefits.

 

All they are really are bitmaps, so they're useful for reflections and stuff, but the main thing that sets them apart from "normal" bitmaps is that they can store values above 1.

 

This means that if you use a bitmap of the inside of an apartment with a big, balcony window in it on a sunny day, and you smack a metal teapot in the scene, it'll reflect the surrounding nicely. The problem, though, comes with the bright areas. Say your material is half grey in colour, and 50% reflective. Obviously the light coming from outdoors through a window on a bright day would be super bright, yet if you're using a normal bitmap for a texture, the window will only show up as a dull, uniform, grey sludge in the reflection (since reflections are at 50%, and 50% of 255 white = 128 grey ... Well, it's not quite that simple, but it's similar).

 

With HDR's, however, you can store values higher than 1. So whilst all the interior of the apartment map is between 0-255 in value, the window might be four times 255 white. In that case, halving that would still leave us with reflections that are double "pure white", whilst those in the interior are dulled down as they would be by something that's less than 100% reflective.

 

This also means you can light with it - it can effectively map the values of the HDR to a light-emitting sphere around the scene (which is basically how a skylight works). The higher the values on the map, the greater the light emitted at that point. If you put in a non-HDR bitmap you usually end up with a mucky looking lighting setup because nothing is particularly bright or dark. However, if you add in parts of the image which go well beyond 255, as the window would in an HDR file, then suddenly you have one area of the image which is far far bright, meaning it actually casts shadows in the scene. This is incredibly useful if you're doing a bit of VFX'y camera matching; Say you're doing a viz shoot for a a new mobile phone, and it's on a table in said apartment, during the photoshoot you could, either using a chrome ball or a fancy 360 degree camera, take a perfect HDR from the place where the 3D telephone is meant to sit. When you get back into your software, you should be able to use that scene for both perfect reflections and perfect lighting (perfect inasmuch as they accurately resemble the original photograph that you're matching to).

 

So they're super useful!