Reflections won a sculpted model
A reflective model reflecting light from an Automatic Sky
A reflective model reflecting light from an HDRi Sky with sun and clouds.
A reflective model reflecting light from an HDRi image of a city scene.
Reflections on an Airstream Camper
Image of an Airstream rendered with an HDRi sky. The HDRi image provides a background as well as the correct illumination, shadows and full 360-degree reflections.
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.
Comparison to non-HDRi rendering
This second image was rendered using the default SketchUp Sun. Compare this to the image above which uses HDRi skies.
There are a number of notable improvements in the HDRi image including softer shadows, softer lighting and reflections that match the background image.All of these improvements help to add to the realism of the model.
Same model with reflection from an normal, "Automatic", sky.