HDRi Images and Backgrounds

HDRi refers to the use of HDRi (High dynamic range imaging) images for illumination or backgrounds.

HDRi skies are a great way to improve any scene you are rendering. It is a quick and accurate way to give the user a high quality background image and illuminate the scene using the HDRi light intensity and colors.

One of the benefits of HDRi skies is the fact that the background image is in the shape of a dome, providing a full 360 degree background. This means that no matter what angle you are viewing your model from, there will always be a high quality background image. This also makes them valuable for scenes which contain reflection – reflective surfaces like this Camper, or windows.

And the separate lighting channel contained in the HDRi image provides better shadows and illumination than just the sun, or plain sky. This lighting information allows some parts of the sky to illuminate the scene more than other parts even though they have the save RGB (red, blue, and green) values and look identical.

HDRi Images

A typical HDRi image consists of a complete sphere to represent both the intensity and color or the Sky in all directions.

Here is an example of a 360 degree HDRi image of a sunset.

(Image courtesy of hyperfocal design)

HDRi Rendered Sample

Here is an example of a model rendered using HDRi for background and illumination.
Notice the soft shadows, background and reflections provided by the HDRi sky.

(Rendered with IRender nXt)

Here is the same model rendered with just the SketchUp sun.


Creation of HDRi Images

Samples of HDRi skies.
Notice how each image covers a full 360 degree Spectrum.
(Images courtesy Evermotion)

Many HDRi images are made by photographing actual scenes.

  • A 360-degree image is created – either with a special 360-degree camera – or by stitching together 3 of 4 images from a single camera after rotating it.
  • Then three images are create – underexposing one image and overexposing another. When combining the 3 images, the RGB of the the middle image is used, but the other two images an be used to determine the intensity of illumination because brighter places will overexpose faster than places which are not providing illumination.


Sources of HDRi Skies

Samples of HDRi skies.
Notice how each image covers a full 360 degree Spectrum.
(Images courtesy Evermotion)

HDRI Skies are available at:
www.accustudio.com – go to Exchange and then HDRI.


See Also


(This content was originally stored on the SU Wiki. Used with permission of the authors.)SuWiki