windows glas composting

[mrmint1982]

Can anyone help me further? I would like to know what is the optimal workflow for interior renderings for composting. If I deactivate the rendering of the refraction part for the sky, I miss this part for all objects in the image. Is it possible to switch off the refraction part only for the window glass so that I have no problems later in Photoshop. I.e. window glass black without sky plus alpha.

What would be the optimal workflow for this?

Many thanks in advance.

[James Vella]

Do you mean propagate masks through refraction (on the glass material)?

[mrmint1982]

Thank you very much for your answer! The alpha is already correct. I already knew that. I'm more concerned that I have the white sky in the RGB image. For compositing, however, it would probably be better if the sky were not included in the RGB at all. See screenshot. But maybe I'm doing something wrong. I usually get white boarders when compositing in Photoshop. But maybe I'm doing something wrong there too. What is the optimal workflow to merge the windows perfectly with an image in Photoshop. If I hide the sky in the refraction part it would work better for compositing. My problem is that the sky is then missing in every refraction object in the scene. For Example Glasses on a table. Not only in the window glass.

[James Vella]

Well in that case you could just use a Direct Visibly override in the render settings, let me know if that works for you.

[mrmint1982]

I have tried it. I think what I want can only be achieved by rendering twice :-(! But I actually wanted to avoid that. I also found a setting in the glass material. Unfortunately, the refractive part of the sky is also missing in the glass.

[James Vella]

What I mean is direct visibility override (black) should fix the ailising issue along your windows while keeping your reflections/refractions as they were in the glass. Just make sure you keep your glass material as it was previously.

[mrmint1982]

When I perform this action, there is no change in the window glass. The glass still displays the sky. I encounter the same issue as shown in the screenshot. If I override it in refraction, the alpha is perfect. However, this results in black areas in the glass on the table. As mentioned before, I believe it's not feasible to have refraction within the room (glass on the table) and no refraction (sky) in the glass of the windows, which would correctly calculate the alpha. I think I'll need to render it twice when I have this cases.

[James Vella]

What are you using for the sky? Is it a corona sky, an image, an image on a plane? etc. Be more specific since there are many ways to include/exclude things but it depends on your setup.

[mrmint1982]

Thank you very much for your help! I just use a Corona Sky + Sun for the rendering.

[James Vella]

What happens if you put a CoronaRaySwitchMtl in the refraction/reflection of the foreground glass object then put the sky material in that? In this case you would still have your Refractions override (black) in render settings:

[mrmint1982]

That has now worked! That was pretty tricky. Fortunately, this doesn't happen that often. Thanks again for your help!!!

[BigAl3D]

Wait, so your issue was using that sky to light your scene, but also have an alpha for the windows to put another image in the background and you would see white edges on the alpha? If that is correct, I put a Corona Compositing tag on the Sky and turn OFF Seen by Camera. This removes the white edges in the alpha for me, assuming this is the issue you had.

If I know what backdrop image I want to use, I add a large plane pointing at the camera. Add a Compositing Tag to this plane to ONLY be seen by camera. I can just slide this plane around until it looks good and render. In this case, you don't have to worry about the alpha.

I can post examples later if this fits your issue, but maybe I don't understand fully.

[mrmint1982]

Unfortunately, this only works if there is no glass in front of the Sky. But I now do it as described by James Vella. Such cases where a glass is in the foreground are very rare. Nevertheless, thank you for your contribution

[James Vella]

You're welcome @mrmint1982

[BigAl3D]

Oh interesting. I have not tried my way with objects outside of the structure.