Modeling a Complex Structure - Google SketchUp Workshop: Modeling, Visualizing, and Illustrating - page 221

Clicking on each tag reveals the setup options: For Radiosity, the most
important option is Type. Here, you can choose between Radiosity and
Ambient Occlusion. The latter produces results that are almost indistin-
guishable from Radiosity, but with significantly faster rendering times.
The other two parameters that need to be noted are Intensity (brightness)
and Samples. The Samples parameter is particularly important, because
the higher its value, the fewer rendering artifacts there will be in the final
image - but, of course, rendering time will increase. Values of around 150-
200 produced the best trade-off between quality and rendering time for this
project. Values of around 40 were used to run quick lighting test renders.

FiG 12.20 Choosing Ambient Occlusion reduces rendering time: Typical values for Radiosity are shown.

To set up the HDRI render, a file in .hdr format needs
to be loaded into the HDRI tag. Images with the .hdr
extension are high dynamic range images. They
contain 32 bits per R, G, and B channels, as opposed
to the standard 8 bits for formats such as JPEG and
TIFF. Since the primary source of illumination in this
model is daylight, an image of a partially covered sky
was chosen. If the image is already in .hdr format, so
much the better. If not, and if you have a Photoshop
license, you can convert any 8-bit image to .hdr
format in the following manner: From the Menu Bar,
choose Image > Mode > 16-Bit, and then Image >
Mode > 32-Bit. This has to be done in two stages,
because 8-bit images cannot be converted directly
into 32-bit images.

FiG 12.21 Setting up the HDRI tag.

For architectural projects, Panoramic projection for the HDR image is the
correct choice in 99% of the cases: It avoids any “seams” in the image when it
is used as a backdrop to the scene. The values for the Power and Clamp Power
parameters will be different for each scene, according to the already existing
illumination, the intensity of the Radiosity setting, etc.