<p dir="ltr"><br>
On Mar 10, 2015 1:44 PM, "Jason Clarke" <<a href="mailto:jason.clarke0@gmail.com">jason.clarke0@gmail.com</a>> wrote:<br>
> Why does it do this? Is there a way to disable it? It makes it impossible to store anything in a texture's alpha channel except actual transparency. Trying to store something like bump or roughness data in the alpha channel will ruin whatever is being stored in the RGB side.</p>
<p dir="ltr">Technically I believe it assumes associated alpha. This is because associated alpha is the only correct method to represent light, and as such, OIIO relies on this implementation.</p>
<p dir="ltr">That said, associated alpha doesn't prevent you from storing values in the RGB data with zero transparency. A set such as 13.5,0.0,0.0 with an alpha of 0.0 is perfectly valid, representing pixel with no occlusion and emitting light.</p>
<p dir="ltr">I would think this has more to do with your chosen file format perhaps? Have you tried with EXRs?</p>
<p dir="ltr">With respect,<br>
TJS</p>