What is hdri rendering? I have been seeing around in the WIP section and I like the results, but alas I know not what it is 
HDRI stands for High Dynamic Range Image, a special format that holds more color and luminosity information and any other image format.
HDRI rendering uses lightprobes (usually 360 degrees photographies of an environement in HDR format) to reproduce a special type of lighting with great accuracy.
Martin
Thanks is there any good tutorials?