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676 Chapter 20: Managing Scenes and Projects
percentage of the image covered by pixels of that
brightness. Histogram features are:
• T he histogram supports several display modes,
which you can choose by right-clicking the
histogram display w indow. The menu lets
you choose between linear and logarithmic
display, automatic or manual x-axis scaling,
y-axis scale options, and which channel is
graphed: luminance, red, green, or blue. The
menuentriesX-AxisScaleandY-AxisScale
are simply labels, and are thus unavailable for
choosing.
• The vertical scale slider on the left side of the
histogram lets you adjust the automatically
computed vertical scale.
• To modify the luminan ce “window,” set X-Axis
Scale to Manual and adjust the minimum and
maximum values in the numeric fields below
either end of the graph.
• The background coloration indicates several
pieces of information:
• T he area between the black and white points
is shaded gray.
• The area below 1.0 (low dynamic range)
is a lighter shade of gray than the area
with luminance greater than 1.0, the high
dynamic range region.
• The background of the region outside the
currently selected blackpoint/whitepoint
region is tinted pink.
• T he ver tical dotted lines indicate integer
spacing (for example, 1...2...3...4). To see
these, the maximum luminance value must
be greater than 1.0.
• You can drag w hitepoint/blackp oint markers
in the histogram to place them visually. The
hot-spot is two pixels to either side of the
marker line. White point select ion is tested
first, so if the two lines are right next to each
other, the white point will be selected.
• You can set the display itself to linear or
logarithmic mode. Logarithmic display remaps
all values greater than 1.0 to a logarithmic
curve. The dotted spacing indicators are
supplemented by heavier dotted lines that
indicate when the scale has changed by a factor
of 10. This is useful for most HDR images, as
the HDR data is usually spread out over a wide
range.
• SettingX-AxisScaletoAutomodecausesthe
histogram to encompass the entire spectrum
of the image. I f you switch back and forth,
prev ious manually set values are preserved and
restored.
File Loading Parameters group
Stor age Bu ff er Format—Specifies the format in
which the image data is stored within 3ds Max. The
base types are variations on 8-bits-per-channel
and 16-bits-per-channel integer formats. There
are two forms of each: one with alpha (RGBA)
and one without alpha (RGB). If you are loading
an image with an alpha channel but don’t require
thealphadata,choosetheRGBversiontosave
some memory. If you choose a storage type that
supports alpha, but load an image without alpha,
no memory is allocated for the alpha channel;
the loader detects the situation and reverts to the
alpha channel-free storage option with equivalent
RGB bit depth.
The options supports the HDR bitmap
storageoptions. Thisallowsstorageofthe
high-dy namic-range data within 3ds Max in three
different HDR formats: 24- and 32-bit LogLUV
formats and 32-bit RealPixel format.
EXR files loaded using these storage mo des
are suitable for use as environment maps for
reflections and skylight.
Color Transform—Because EXR images often
contain values bri g hter than “white,” it is often
desirabletochangetheluminancerangeinthe