Premultiplied vs. Un-Premultiplied Color Channels
The A, AR, AG, and AB channels in an OpenEXR image represent alpha or opacity: 0.0 means the pixel is
transparent; 1.0 means the pixel is opaque. By convention, all color channels are premultiplied by alpha,
so that
composite = foreground + (1-alpha) × background
performs a correct "over" operation.
Describing the color channels as "premultiplied" is a shorthand for describing a correct "over" operation.
With un-premultiplied color channels "over" operations would require computing
composite = alpha × foreground + (1-alpha) × background
"Premultiplied" does not mean that pixels with zero alpha and non-zero color channels are illegal. Such a
pixel represents an object that emits light even though it is completely transparent, for example, a candle
flame.
Aug 18, 2010
Quotation "Premultiplied vs. Un-Premultiplied Color Channels"
quote from Technical Introduction to OpenEXR.
Aug 13, 2010
Aug 6, 2010
A particle trail node plug-in for Maya
I've made a particle trail node plug-in for Maya.
It has been adding new function and fixed bug.
It has an error when using Mental Ray batch render.
It has been adding new function and fixed bug.
It has an error when using Mental Ray batch render.
I might release it.Error: (Mayatomr.Geometry) : unnamed object is not a mesh, ignoredFix it.
Aug 2, 2010
Sine wave pattern
A sine wave pattern expresses:
position = (sin(frequency * frequency multiplier) * amplitude) + offset
position = (sin(frequency * frequency multiplier) * amplitude) + offset
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