FX-Map Color/Alpha Weirdness!?

[maus]

So it would seam that the FX-Map changes the RGB color values if the Alpha channel is anything other then 1!

Check out the Red value in the first print screen its 255 / 1 and the Alpha is also 255 / 1

Now check out the second print screen, the Red value has been changed 127 / 0.498 along with the Alpha 127 / 0.498

Note that the Float 4 Red value is still 1 and only the Alpha value has been changed to 0.5 this Float 4 is plugged directly into the Color / Luminosity property.

So why is the Alpha also changing the RGB values! This has been totally messing up my colors, and its taken hours to track it down... I have tried changing blending modes and other properties in the FX-Map and its parent nodes to solve this but no such luck.

Any ideas, is this a bug?

Thanks for your help.

^^

[Nicolas Wirrmann]

The fxmap outputs a premultiplied image.
That's why the rgb values are changed when alpha != 1.

You can unpremultiply the rgb by dividing rgb by alpha.

[maus]

Ah... cool that fixed it. Thanks for the helpful answer.

But why premultiply the image?

^^

[Nicolas Wirrmann]

To get optimal performances, doing straight alpha blending is way too expensive.

[maus]

So in the advent that alpha is zero, dividing rgb by alpha crashes Substance Designer...

To prevent a crash and still get out the proper color value what should I do?

Thanks for your help.

^^