Here you won't find a what a HDRI is, but how you can make one.
A little warning at the beginning: HDR-Images are not normal RGB- Images, they are build of different exposed photographies and that's why they can get real big. You also have to be very precise during the prozess of making a hdri to get a good result.
1. How to photograph
HDR-Images can be used as spherical enviroments but also as normal textures. You need lightwave to use them but the first new renderer are in betastage which will understand that format too.
What do i need?
The best way to photograph is with a digitalcamera, because you can be sure to get pixelprecise results ,while if you are scanning from a photo you also have to rotate the azimuth. Some Digitalcameras don't give you the chance to change the exposure time, but you can change the imagebrightnes and the camera stores the informations about exposuretime internally to your jpg-file. Well, photoshop or in this example ACDSee can read these information.
If you have a digicam where you can sett the exposuretime manualy don't forget the f-stop.
What have i do with the pictures now?
We only have to crop the image:
Your images should look like that now:
If you have written down the exposuretime you are ready for the funny part....
We now have five images
which have to be kompiled to a HDR-Image.
This Software makes from many singleimages one HDR-Image. There is only one problem with this Software: it needs PPM-Images.
But there is a solution for the problem: when the JPE-Group released their imageformart they also gives away a encoder, and with this encoder also a decoder, which can convert any jpg to a ..yes, ppm. You can download it from here .... This is not my software, so i can't garantee you that this software is ok!!!!
to use the Software more easier i have put it in a RMB-command.
There is another port
of this software which can read tga's.
Problem solved, so we can go on with Mkhdr.....
3. setup MkHDR
Mkhdr.exe is a Comandlinetool and need external options and something like a scenedescription. With the scenedescription you let mkhdr know what it should do with the files.
In this Textfile you
have a list with your imagenames , exposuretime, f-Stop(?) and two options
which are not important for the quality.
Wald_1000.ppm 1000 4.4 3 0 --->name
of the image, 1000=exposure time(1/1000) ,4.4 = f-Stop, gain, neutral
next we create a batchfile
in the same folder as mkhdr.exe
mkhdr.exe -w dummy [path\]wald.txt wald.hdr
the parameter "-w
dummy" is not required but without the parameter mkhdr crashes on
my system......hmm.. ???