2009

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Level setting may need to be increased. When a different preset was
selected (Production to Preview), the refraction levels changed.
There are spotted areas on the table surface directly in front of the
bottle. This can be corrected by adjusting the photon quality settings.
The desired caustic effect in the shadow has appeared but is not very
pronounced. You want to achieve an effect where the shadow has
brighter regions as a result of light being refracted through the surfaces
of the bottle.
Adjusting the refraction levels
When the refraction levels are set too low, light rays do not refract through
all of the surfaces enough to provide a realistic indication of a translucent
surface when raytraced. This results in the object appearing opaque when it
should appear translucent.
Increasing the Refractions setting allows the renderer to calculate what is seen
through the surfaces of the glass by allowing the light rays to refract the correct
number of times.
In the next step, you change the Refraction settings so that the bottle will
appear translucent when rendered.
To increase the refraction levels
1 In the Render Settings window, select the Quality tab and then open the
Raytracing attributes.
2 In the Raytracing section set the following:
Refractions: 6
Max trace depth: 8
The Refractions setting sets the number of times a light ray can be refracted.
When the setting is too low the ray does not penetrate through all of the
surfaces. The Max Trace Depth setting limits the total Refraction and
Reflection settings. By setting it to 8, you ensure that two reflection and
six refraction calculations can occur.
Photons refract in a manner similar to light rays when rendering. Increasing
the Refractions setting for the Caustic Photons ensures that the renderer can
correctly calculate the caustics that should occur with the bottle. In this case,
468 | Chapter 9 Rendering