The most common is an average of all three color channels but sometimes it may be useful to use a specific color channel instead. The selection algorithm specifies how Lumiere should calculate which pixels to select for diffusion. Left: Source image, Right: glow threshold selection Pixels with a luminance value greater than this threshold and less than the upper threshold will be selected for diffusion. Lower Threshold: This slider controls the lower tolerance for selection. The diffusion is additively composited with the original image using a specific blending mode to produce a diffused glow. Certain coloring operations can also be performed at this time to generate a suitable diffusion. This blurs the selection to a specific size. These pixels would generally consist of the brightest pixels in the image such as a light or sun, and the upper threshold would generally be left at 255. A typical workflow is as follows: a selection of pixels is first specified using the lower and upper threshold. These sections have been logically separated into their own panel groups in Lumiere’s GUI for the sake of clarity and ease of use. First is selection, next is diffusion and final is output. Lumiere performs it’s operations using three logical steps.
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