Maxwell Render | Official public forum

Is there anyway to get an alpha map for the sky via the plug-in?

Have you tried enabling Alpha in Scene Manager > Output > Channels? Note that you only see the Channels panel if you have enabled Advanced View in the page; the toggle for that is in the toolbar, next to the undo/redo buttons.

Thanks, that worked perfectly.

JD, could you perhaps elaborate a little on the Alpha settings; "Opaque" and "Embedded".
My AGS materials stay grey in the alpha channel, when rendered with Opaque. I thought all transparent materials should go all white?
And the "Embedded" doesn't produce an image with transparent pixels even though I use .tga or .tif as file format.
Maybe I got those functionalities wrong...
/Stefan

You would be better to ask that question in the general Maxwell forum, since I'm no pro when it comes to compositing workflows...Tom or Mihai would have your answer.

JDHill wrote:Tom or Mihai would have your answer.

Alright, thanks

Stefan,

AGS materials don't seem to become opaque, as you say, with Opaque checked. I think that feature only works with real glass.

As for Embed. I believe that the only way to get that to work is to open the MXI and save from there. Are you doing that? I think that when you just hit render the images produced are always separated - again, I don't know why.

-Brodie

Thank you for commenting on this, Brodie!

If the Opaque feature only applies to "real glass", it is more or less useless for me, since I mainly use AGS in arch vis

Embedding the alpha-channel in the render output file would be soo great, though.
I keep struggling with applying alphas in the most correct and clean way, avoiding black matte, using different blending modes in Photoshop etc.
You'll find post after post in the forum where users ask "how to" use alphas. Good (and often different) solutions are replied, usually requiring quite a few steps in post editing.
I'll definitely try and re-open my MXIs (or manually save the render after stopping the render process) to get the transparent pixels embedded right into my render output
But I guess the most intuitive and simple procedure would be to get the Embed option only when choosing an output file format that supports transparencies, and then get an output with the alpha embedded straight away.
Wishful thinking, perhaps

As JD says, this has probably nothing to do with the plugin. I'll ask in the general forum later...

/Stefan

If the Opaque feature only applies to "real glass", it is more or less useless for me, since I mainly use AGS in arch vis

Yep, worthless for me as well.

You'll find post after post in the forum where users ask "how to" use alphas.

Ya, I hear you there. Apparently this is more of a Photoshop issue than a maxwell issue. I can give my take on doing alphas if you'd like. I struggled with it quite a bit before having a very long conversation with Tom about it. It's about the closest thing I know of to a 'correct' way of doing it and involved at least one aspect of photoshop I hadn't heard here before.

But I guess the most intuitive and simple procedure would be to get the Embed option only when choosing an output file format that supports transparencies, and then get an output with the alpha embedded straight away.

Agreed. That only seems intuitive. If you choose Embed and it ever gives you anything else it seems like a mistake to me.

-Brodie

Just to clarify something on the AGS vs. alpha thing: it is not possible to differentiate, analytically, a material which you consider to be 'AGS' from one which you consider to be semi-opaque plastic, metal, etc. You may create it using Opacity < 1.0 in a given layer, or within a layer, by means of an Nd=1.0 'ghost' BSDF. Logically, code cannot blindly assume that you mean to say 'AGS' when it sees such conditions; that may not be at all what you meant.

So, to get an opaque alpha from AGS, it would be necessary to add an explicit layer- or material-level switch, i.e. Opaque for Alpha.

Maybe I'm not grasping the technical side of what you're saying, but shouldn't that be essentially what the Opaque checkbox does? If it finds a material with less than 100% opacity it should adjust it to 100% opacity for the alpha.

In other words if each material had it's own Opaque for Alpha switch what the current Opaque checkbox should do is go into each material and switch that to ON.

-Brodie

The problem, I think, is that where dielectrics are dielectrics, AGS materials are just a subset of all non-opaque materials. So where you can treat all dielectrics the same, you cannot do so for all non-opaques.

To illustrate, consider a building with an AGS facade, surrounded by non-photorealistic billboard trees which are semi-opaque (I have this in one of my user test scenes). Currently, you'd need to temporarily make the AGS opaque and render with Opaque Alpha off to get the result you want (i.e. facade opaque, trees semi-opaque). If, on the other hand, Opaque Alpha were changed to interpret all semi-opaques as opaque, while it is true that it would then automatically handle the AGS the way you want, it would also interpret the the trees as being opaque. So in either case, the Opaque Alpha feature would be useless for you: even with it 'fixed', you would have to choose between turning it off and handling the facade manually, or turning it on and obtaining an undesirable result for the trees. That's why I say you need a switch.

Ah, I hadn't considered clipmaps. That makes more sense.

-Brodie