Render only masks and alpha

[romullus]

I wonder why alpha is considered a shading element? Why it is not rendered when render only masks is selected?

[TomG]

I think (and the developers can say if it is otherwise) because material properties come into play, like opacity and refraction, which require the actual render engine to calculate (while masks don't depend on anything from the light transport calculations).

[romullus]

Ah, now i see. Although it would be nice to get free alpha when no refraction/opacity is involved :]