Hide mesh but use reflection from it

[Engie]

Hey

I would like to use mesh as a reflective material so I can bend and twist the mesh, but I only want the reflection to be rendered that is coming form the mesh and the mesh hidden.

One way I have found I can do this is to lower alpha on principle bsdf, but this severaly fade the reflection also. I know there is better way ,but I don’t know how to do it so please help me out

If possible I would like be able to see the reflection on the view port as well while I’m workin so not only when I render image.

Here’s a file example where I have reflective mesh under cube. This is the arrange ment I will be using on my work too.
hide mesh but keep the reflection.blend (872.3 KB)

[123ERTYY (Crazerep)]

hello, try unchecking the box under object properties of the cube and see

[Engie]

This hides the reflection of the plane as well so no go.

[magpie]

The Glossy option in that set is the one that controls whether it shows in the reflection.

[Engie]

I don’t understand what you mean ?

[Engie]

If I turn camer off from Ray visibility it hides the plane and the reflection and only cube is left here’s a picture.

[magpie]

Do it on the cube object, not the plane.

That way the cube won’t be seen by the camera directly, but it will show up in reflections.

[Engie]

I don’t think you understand what I’m after here. I want the cube to be visible. I also want the reflection that is coming out of the plane to be visible, but hide the plane and leave the reflection on so it’s like transparent plane that reflects the cubes emission. and If I use that camera off to cube it only hides the cube like it hides the plane.

[magpie]

Try changing the material on the plane to a Glossy BSDF shader.

That will work if you have a plain background color, as the plane will be reflecting that solid color as well as the cube.

If you want to put it into a scene with more objects, then you may need to look at doing something in the compositor. Or set the object visibility of those objects to not have the Glossy option checked.

[Engie]

If I use glossy on cube it hides the cube and leave the reflections on to the plane, but this isn’t what I want.

Only thing I want to hide is the plane and leave the reflections not the cube.

[magpie]

Put glossy on the plane (the thing that you want to see reflections on).
Leave the cube as it was (assuming that you want it to be visible).

[Engie]

If I use glossy bsdf on the plane this works when the background is what it is on the blend file, but if I use hdr then the plane will be visible as well.

[magpie]

Is your HDR on a ‘sky’ object, like a sphere?
If so, go to the Visibility section for that object, and turn off Glossy.

[Engie]

I use hdr as worlds enviroment texture to light the scene

[magpie]

Actually, there are visibility options for the World too.
Look under the Ray Visibility section in the World tab.

You can turn off Glossy there too. Although that makes the rest of the plane solid black.

[Engie]

here’s how it looks if I take glossy of from worlds ray visibility so no go.

[Engie]

since I haven’t found solution to this on the net it could be possible that this just isn’t possible and reflections are bound by code to the mesh and alpha channel like I mentioned at the beginning only makes the mesh transparent since it fades it out from view and thus also fade out the reflections on it too.

[magpie]

It is possible, but it needs you to render different passes, and bring them together in the compositor.
This is a decent tutorial of the process: https://youtu.be/cr4828-YfSU

[DNorman]

Yes, you need to use the compositor for this.

One way is to put the cube and plane in a black world and use the black as a mask to add a background rendered in a different scene.

If you flip the images :

[Engie]

this as an isolated case works, but when I have alot of stuff in a scene where I need to use this I think it’s not possible since I need to separate about 100 other mesh object from the sun and the reflection so how’s that work then ?

I also use sompositor to add bloom effect to the whole scene

Also could you share the compositor file I don’t know what is “greater than” node.