I would like to know in blender (internal) if premultiplied alpha is the same effect of "alpha clipping" in the alpha blend mode?
I have found this :
The transparency information is stored in the alpha channel and also in the visible RGB channels, which are multiplied with a background color. The colors of semitransparent areas, such as smoothed edges, are tinted in the background color in proportion to their degree of transparency.
If white pixels have a value of 1 (figure) and black pixels a value of 0 (transparent background) and multiply them by the pixels of the RGB image, pixels multiplied by 1 will maintain their values while pixels multiplied by 0 , Will become black. The problem comes when it is a value between 0 and 1, that is, a grayscale.
When composing these types of images on another background is when problems often occur. These are evidenced in the contours where, due to antialiasing or other effects, some of the pixels are gray, thus they are semitransparent. When composing our images, that semitransparency will show the black pixels of the background. When in addition, the alpha image contains motion blur, the problem is usually much worse, since it increases the number of pixels affected by the premultiplication."
that is a theory ,but I would like to inherence in blender.