Monday, December 20, 2010

Creating HDRi Backgrounds

The latest version of IRender nXt includes a button on the Background Setup Tab to create a HDRi image from a normal, "tone mapped", image.

You can use a, (non panoramic), HDRi image as a background.

Settings for Inverse Tone Mapping 
Tone mapping, (converting from HDRi to normal images), takes luminance and creates RGB colors for display or saving in an image. Inverse tone mapping reverses that equation. nXt's tone operator requires two other pieces of information in order to invert it properly-- the average luminance and the maximum luminance of a scene. The way it works at the moment is that you select Daylight, Nighttime to get default values, and then adjust the custom settings for Average and Maximum illumination in the image.

Lumens and Default Values
After selecting a normal, ("Tone Mapped"), image, you can set the Average Lumens and maximum Lumens which control how bright the image will appear.
  • Daylight 5,000 and 20,000
  • Nighttime 1 and 500
Load this image as a Planar HDRi Background 
After converting your image, you can load it as a HDRi background for rendering.

Image Adjustments
If you use a Planar HDRi background with the [[[Path Tracer]], you can adjust its brightness as an additonal lighting channel after rendering. (This is not working with the standard renderer yet)