Hi Marcus, thank you for the quick answer.
In fact I gave my conclusion according to the equations.
In A_ONE mode, we have :
result.r = fb.r * (1.0f - transparent.a * transparency) + mat.r *
(transparent.a * transparency)
Let’s set transparency to 0 :
result.r = fb.r * (1.0f - transparent.a * 0) + mat.r * (transparent.a * 0)
= fb.r * (1.0f - 0) + mat.r * (0)
= fb.r
==> in A_ONE mode, transparency = 0 make the material fully transparent, thus here 1 is the neutral value.
In RGB_ZERO mode, we have :
result.r = fb.r * (transparent.r * transparency) + mat.r *
(1.0f -transparent.r * transparency)
Let’s set transparency to 1, and transparent values to 1 (fully transparent):
result.r = fb.r * (1) + mat.r * (1.0f -1)
= fb.r + mat.r * (0)
= fb.r
Let’s try with transparency = 0, and transparent values to 1 (fully transparent):
result.r = fb.r * (1 * 0) + mat.r * (1.0f -1 * 0)
= fb.r * 0+ mat.r * 1
= mat.r
==> in RGB_ZERO mode, transparency = 1 means fully transparent… a value of 0 make the material opaque, whatever the transparent color is.
Moreover, according to the equations, in A_ONE mode the transparency value modulate the transparency material (the less transparency value is, the less transparent is the material), whereas in RGB_ONE mode the transparency modulates the opacity of the material (the less transparency value is, the mode opaque is the material). As in both mode the transparency has not the same even, it cannot have the same default value for both modes.
Maybe I’m totally wrong, but in that case I don’t see my mistake.