<div dir="ltr"><div>Hi,</div><div><br></div>It is not "associated" it is "premultiplied" in context of blender and would be nice if this terminology is followed in discussions.<div><br></div><div>OIIO is not really relying on any alpha treatment, it just gives you whatever you're requesting to as far as i concerned. But what Cycles expects from the images is also depends on the shader setup, so having a look into setup and image which gives issue to you would help investigating if it's some issues with setup or some bug or some lack of proper CM in Cycles.</div><div><br></div><div>It is also to be mentioned, that all the CM work we did for image input in blender is to be still re-done for Cycles. So it'll respect input color space, alpha type and so on.</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Mar 11, 2015 at 2:40 AM, Troy Sobotka <span dir="ltr"><<a href="mailto:troy.sobotka@gmail.com" target="_blank">troy.sobotka@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><p dir="ltr"><br>
On Mar 10, 2015 1:44 PM, "Jason Clarke" <<a href="mailto:jason.clarke0@gmail.com" target="_blank">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>
</span><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>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div><span style="color:rgb(102,102,102)">With best regards, Sergey Sharybin</span></div></div>
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