Alpha for materials

[janko22]

Is it possible to have separate Alpha outputs for different materials to isolate them?
It's not working like it should, with grouping in shader tree.
I've tried to use modo's render for Alphas and Vray for main render but it's not working because when you compare modo and Vray alpha in PS they are not exactly the same (difference blending).
Thanks

[vladimir.nedev]

Yes, this is not possible currently in V-Ray. We are planning on implementing this, but may be in not exactly the same way.

Is it more convenient to have separate images for each object, or would it be better if all the object masks were in one image,
with different colors, so you can select them in post ?

Greetings,
Vladimir Nedev

[janko22]

For me it's better to be able to have separate alpha for selected object/material. Selecting colors with magic wand in PS is never really precise. Also for post work in animation it's better to be able to have alpha sequence that can be used as mask.

[janko22]

Hi, is there any news on this?

[vladimir.nedev]

Hi, is there any news on this?

Not yet, sorry.

Greetings,
Vladimir Nedev

[peterL]

yeah a alpha connection would be awesome ... ... it is a must in post for me

would be great if it would just work as it does in modo, a node variant would be fine as well ...

thx vladimir

[vladimir.nedev]

The nightly build from tomorrow (the one from 2015-06-16) will have support for masking on Alpha Render outputs.
This change will be in the 3.00.07 open beta build as well.

Please give it a try, since I am not 100% sure I've implemented it correctly.

Edit : Note that it does not work in RT GPU for now.

Greetings,
Vladimir Nedev

[janko22]

Thank you Vladimir, I'll test it today.

[cyroz]

Thank you Vladimir, I just checked it this mornig, and it worked as expected!
Thanks again!

[janko22]

Yes masking works as expected on materials.
I found that alpha in material group is somehow color corrected, it's not black and white as the main alpha. You can test this by lowering burn value to 0.1 and alphas in material groups become grey and the main alpha remains white. Also I think that antialiasing is slightly different to the main alpha (it become really obvious if you turn on Matte Surface in Vray object properties tab on the main shader). I've tested all this on a simple cube with 3 materials and 3 alpha outputs in material groups + main alpha output.
Thanks again Vladimir.

[vladimir.nedev]

Yes masking works as expected on materials.
I found that alpha in material group is somehow color corrected, it's not black and white as the main alpha. You can test this by lowering burn value to 0.1 and alphas in material groups become grey and the main alpha remains white. Also I think that antialiasing is slightly different to the main alpha (it become really obvious if you turn on Matte Surface in Vray object properties tab on the main shader). I've tested all this on a simple cube with 3 materials and 3 alpha outputs in material groups + main alpha output.
Thanks again Vladimir.

Yes, the masked alpha render outputs respect the "Image processing" option and if it is on, they have color mapping applied to them.
But I guess it doesn't make sense. Should I disable the color mapping for them ?

They also respect the "Antialiasing" option of the render output item as well. If it is on, V-Ray will try to anti-alias the masked alphas as well, together with the final RGB color.

Greetings,
Vladimir Nedev

[janko22]

I don't know, I think masked alpha outputs should be treated the same way as the main alpha output (antialiasing and color mapping wise). So yes to antialiasing and no to color mapping from me.
And in my test antialiasing is different in masked alphas and in the main alpha ( please make it the same as in the main alpha).

[vladimir.nedev]

I don't know, I think masked alpha outputs should be treated the same way as the main alpha output (antialiasing and color mapping wise). So yes to antialiasing and no to color mapping from me.
And in my test antialiasing is different in masked alphas and in the main alpha ( please make it the same as in the main alpha).

Can you attach the scene with the different anti-aliasing, and maybe a screenshot to show me what you mean.

Greetings,
Vladimir Nedev

[vladimir.nedev]

For tomorrows nightly build (the one from 2015-06-17) the color mapping is disabled for the masked alpha render outputs.
The color mapping was always disabled for the main alpha render output.

Greetings,
Vladimir Nedev

[janko22]

Here is alpha in material group:


Here is the main alpha:


And here is difference blending in Photoshop:

You can see that there is a white line, the image should be completely black if the two alpha outputs were the same.

Also if you turn on Matte Surface in Object properties you get this:
: