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Glacial Erratics


Glacial Erratics


This image was started as an exercise to capture my experience winter climbing at a crag overlooking the Connecticut River with Ken Nichols. As with many images that are started with a simple intent, it quickly moved out of control and produced something unanticipated. Indeed, it quickly became a component of the Expedition diptych.

The name of the image comes from the geological phenomenon that results when a glacier that has been carrying boulders and rocks melts away. It then leaves its deposits in places that may be hundreds of miles from where they originated. Here, even some of the glacier, in the form of the ice cube, is left behind.

One of the areas of interest from a technical perspective is the use of a lighting array to create the soft shadows.

Top View Of Lighting Array
Front View Of Lighting Array

There are many different arrangements possible - this one worked well for my image, which needed to simulate soft shadows from a directional light source. A more symmetrical distribution of lights would be needed to simulate the lighting of an overcast day.

The ice cube presented a number of problems, not least of which was its very long rendering time - so every experiment took ten or more minutes to render, even at small sizes. I started with two nested cubes. One had a cloud in it, and the other was the outer "ice" surface - moderately refractive and reflective, extensively bumpy. I spent some time getting the look right, but the color was wrong. Nevertheless, the result was interesting.

Alternate Glacial Erratics

Obviously, this is more like florite than ice, but there is a nice color to it that works with the rest of the piece. Still, I proceeded to whiten it by reducing the refraction level.

Another issue that arises is beyond the Bryce renderer. That is a "lens" effect that makes for a bright area in the shadow. I added a small yellowish light to illuminate that space.

Only a small amount of post-processing was needed for the final image - adding the beach and smoothing the polygonal edges. Corel PhotoPaint 9 was used.

Copyright © 2004 by Mark Cashman (unless otherwise indicated), All Rights Reserved