PV227 GPU Rendering
Marek Vinkler
Department of Computer Graphics and Design
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tone mapping,
bloom.
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Dynamic Range
dynamic range – ratio between the largest and smallest
possible values of a changeable quantity,
in our case the range of luminances (of a sensor, of the
human eye, of an output device, ...)
not the same for all of these!
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High Dynamic Range Imaging
techniques used to reproduce higher dynamic range than
normally possible.
-4 -2 +2 +4
Figure: Taken from en.wikipedia.org. Acquisition example, multiple
images taken at different exposition (measured in stops).
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High Dynamic Range Imaging (cont.)
Simple contrast reduction Local tone mapping
Figure: Taken from en.wikipedia.org. Acquisition example, the
composed image.
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Tone Mapping
mapping one set of colors to another to approximate the
appearance of high dynamic range images in a medium
that has a more limited dynamic range.
raw exposure adaptive
Figure: Three tone mapping approaches.
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Exposure Mapping
compute image taken at a particular “exposure” from an
HDR image,
rgb = 1 − 2−hdr∗exposure.
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Adaptive (Local) Tone Mapping
exposure chosen automatically based on image properties,
according to the luminance of neighbouring pixels,
higher exposure in dark regions, low exposure in bright
regions.
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Bloom (Glow)
artifact of a sensor (camera, eye) overwhelmed by bright
light,
artificially added in computer graphics.
Off On
Figure: Bloom effect.
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Bloom (cont.)
separate high luminance pixels (highlights),
blur the highlights to extend them beyond their natural
borders,
compose the two images back together.
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