Any command that opens an image file, such as View Image File > Specify an EXR file. > Click Open. > OpenEXR Configuration dialog
This version of the OpenEXR Configuration dialog appears whenever you open an EXR file. It lets you specify various color transformations to be applied to the loaded image, designate the internal storage format to use, and preview the loaded image with the color transforms applied. There is also a histogram for viewing the brightness distribution in the image and adjusting the white and black points interactively.
To view the histogram, click the Preview button. The histogram displays a detailed bar graph of the distribution of brightness throughout the image. The horizontal axis of the histogram defines the luminance value, and the vertical axis indicates the percentage of the image covered by pixels of that brightness. Histogram features are:
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The histogram supports several display modes, which you can choose by right-clicking the histogram display window. 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 menu entries X-Axis Scale and Y-Axis Scale are simply labels, and are thus unavailable for choosing.
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The vertical scale slider on the left side of the histogram lets you adjust the automatically computed vertical scale.
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To modify the luminance “window,” set X-Axis Scale to Manual and adjust the minimum and maximum values in the numeric fields below either end of the graph.
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The background coloration indicates several pieces of information:
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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.
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The background of the region outside the currently selected blackpoint/whitepoint region is tinted pink.
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The vertical dotted lines indicate integer spacing (for example, 1...2...3...4). To see these, the maximum luminance value must be greater than 1.0.
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You can drag whitepoint/blackpoint markers in the histogram to place them visually. The hot-spot is two pixels to either side of the marker line. White point selection is tested first, so if the two lines are right next to each other, the white point will be selected.
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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.
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Setting X-Axis Scale to Auto mode causes the histogram to encompass the entire spectrum of the image. If you switch back and forth, previous manually set values are preserved and restored.
Storage Buffer Format—Specifies the format in which the image data is stored within Autodesk VIZ. 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 the alpha data, choose the RGB version to save 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 storage options. This allows storage of the high-dynamic-range data within Autodesk VIZ in three different HDR formats: 24- and 32-bit LogLUV formats and 32-bit RealPixel format.
EXR files loaded using these storage modes are suitable for use as environment maps for reflections and skylight.
Color Transform—Because EXR images often contain values brighter than “white,” it is often desirable to change the luminance range in the source image over which black to white occurs; that is, to remap the color data. When Color Transform is on, you can adjust these luminance and general brightness controls:
Exponent—The exponent to apply when loading the file
Black Point—Where black should be in the luminance range of the image
RGB Level—A standard multiplier for the RGB data
RGB Offset—An additive offset for the RGB data
Preview—The Preview window provides for interactive previewing of color-transform options for loading EXR files. After choosing an EXR file to open, click Preview to enable the preview window. The image file is loaded into the preview window, and from then on any changes to the Color Transform options update the thumbnail in real time.
The preview window ignores the aspect ratio of the image to make the most of the small screen space available.
Plugin About—Opens a dialog that shows information about the OpenEXR plug-in.
File Info—Opens the File Information dialog, which lets you view file statistics plus any attributes and channels stored in the file.
OK—Accepts any changes, closes the dialog, and opens the image file.
Cancel—Discards any changes and closes the dialog without loading the image file.
This read-only dialog displays basic file statistics including date, time, size, and resolution, plus any attributes and channel information stored with the file. See Extra Channels and Attributes.
