Architectural_Design_with_SketchUp

Architectural Design with SketchUp
created at exactly the location in which the virtual scene will be rendered (e.g., a location for
a new house or a table in a studio where a statue is to be modeled), then the rendering will
have accurate reflections and a correct background image for that location. Because the image
“wraps around” the entire scene, it can also be positioned by rotating it around a vertical axis.
Moving the camera view also looks realistic because the view of the sky background will change.
The most important benefit of using these environments, however, might be that the
image can be used as the sole light source for the scene. This is called image-based lighting
(IBL) and is discussed in the next section. For now, you can simply imagine that the entire
3D scene can receive lighting and color information from the image that was applied to the
background. As a result, a scene that is illuminated in this way is lit in exactly the same mood
(light color and general lighting ambiance) as the location where the environment image was
created. See Figure 5.36 for an example.
Figure 5.36: Scene with spherical sky image and image-based illumination
There are many places on the Internet where you can find spherical skies and sky probes.
The following list of URLs is not at all exhaustive but should help you in your search for the
perfect background image.
www.cgtextures.com—This site has several panoramic (hemispherical) skies
www.kerkythea.net/joomla/index.php?option=com_remository&Itemid=42&func=select&id=11 (Short link:
http://goo.gl/9xlrw)—Various skies and sky probes from the Kerkythea website
http://ict.debevec.org/~debevec/Probes—Some HDR light probes
http://blenderartists.org/forum/showthread.php?24038-Free-high-res-skymaps-(Massive-07-update!) (Short
link: http://goo.gl/r98W7)—Various sky probes and hemispherical sky maps
TIP
You can very easily create sky probes yourself as long as you have a good-quality digital
camera that has high image resolution. All you need is a perfectly reflecting chrome
sphere. You can get one for less than $20 at some material suppliers—the one shown
here is a precision-ground steel-alloy ball from McMaster-Carr (www.mcmaster.com).
166