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1560 Chapter 16: Material Editor, Materials, and Maps
Note that interpolation can cause artifacts.Because
itisdoneonalow-resolutiongrid,itcanlose
details. And because it blends neighbors of this
low-resolution grid, it can cause oversmoothing.
Forthisreasonitisusefulprimarilywithflat
surfaces. Interpolation does not work well with
wavy, highly detailed surfaces or surfaces that use
bump maps.
Interpolation grid density—The resolution of the
grid used for interpolating glossy reflections and
refraction. Choose a setting from the drop-down
list.
Within the grid, data is stored and shared across
the points. Using a lower grid resolution is faster,
but causes greater loss of det a il information.
Reflective interpolatio n group
Neighboring points to look up—Defines how many
stored grid points (in an N by N group around the
currently rendered point) is lo oked up to smooth
out reflective glossiness. The default is 2, and
higher values will “smear” the glossiness more, but
arehencepronetomoreoversmoothingartifacts.
In the following illustration, the reflection of the
left cup in the floor does not use interpolation,
and some grain is evident (here intentionally
exaggerated).Thefloortilesundertheothertwo
cups use a half-resolution inter polation with point
lookup set to 2 (center) and 4 (right), respectively.
Left: No interpolation; Center: Looking up two points; Right:
Looking u p four points.
Theprecedingimagealsoillustratesoneofthe
consequences of using interpolation: The foot of
theleftcup,whichisnearthefloor,isreflected
quite sharply, and only the parts of the cup far from
thefloorareblurry. However,theinterpolated
reflectionsoftherightcupshaveabaselevelof
blurr iness, due to the smo othing of interpolation,
which makes e ven the closest part s somewhat
blurry. In most scenes with weak glossy reflections
this discrepancy will never b e noticed, but in other
cases this can make things like legs of t ables and
chairs feel “unconnected” with a glossy floor, if the
reflectivity is high. To resolve this, you can use the
High Detail Distance setting (see following).
High detail di stance—Allows tracing of a second set
of detail rays to create a “clearer” version of objects
w ithin the sp ecified radius.
In the following illustration, all three floor tiles use
interpolationbutthetwoontherightusedifferent
distances for the detail distance.