Create a "blur" material that permit to blur what is behind the object? (Eevee)

Hi,
I don’t know if what I want to do here is possible :
In After Effect we can create adjustement layers that only add the wanted effect to what is behind them, for exemple I can add a blur effect to this layer and so blur the parts of my video I want easily and dynamically this way.

I would need the exact same thing in Blender, ideally a material on a plane that would be invisible but would “blur” everything that is behind it, so I can place it where my scene is too sharp and smooth it.

I hope i’m clear with what I am asking, ideally I need it working in Eevee. Thanks if you have any idea!

Do you mean something like this:

  • in the composition workspace you can add a blur node to blur a render layer (background and object layer) or image sequence/movie clip
  • in the video editing workspace inthe sequencer there is no such feature only some coor modifier (no blur)
  • a nonvisible bluring material is something i never heard of (a think something like a rough glass will do but is much more computing work than a blur filter over a render layer )

Not knowing AE i would guess have a look at the first.

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Ideally I mean a blur effect directly added on a plane that we could move in the scene to decide which part will be blurred by it dynamically, that would be way more convenient in my opinion than having to do in the compositing nodes and do it with layers (i don’t use that much compositor tho). For exemple, If i want to blur my horizon I would have just to stretch the plane at extreemity between ground and sky and make it not sharp.

So yes the nearer to that is kind of a glass shader but that only blur what is behind it without being visible. I never heard about that neither, it would permit to do some realtime compositing, would be great !

Well bluring horizons are done with farer away images and camera lense setting… (depth of view etc…)

If you want a depth of field effect you add that in the camera. You can set a focus object and animate that.

However, if you really want a plane you could put your plane (or any other object) into your scene give it a completely transparent shader and an AOV node. In the AOV node set value to 1 or control it with a texture or something.
Then set up your AOV pass in the passes properties and use the AOV pass to drive a blur node in the compositor. I think you have to set the blur node to “variable size”.

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It depends of the cases, if I have a very sharp edged ground and want it to look more blurred to mix well with what is upper, the DOF only will not be enough. (particulary if the scene is small and so the end of the plane is not that far)

That’s a great and smart exemple thanks you, but not fully work for me : It seems to not work in Eevee, the transparency appear black when set up like this and when I set it to other alpha modes it’s transparent but the blur not show up.
Also, when in first mode it seems to blur what is in front of the plane too, not only what is behind.
Still a very big step near to this, thanks!

Do you just want distance dependent blur?
Then you could use either a mist pass and use that to drive the Blur size or the Z-Depth.
Depending on your scene you might have to normalize the Z-Depth.
Anyway, if you something like a color ramp, an rgb-curve or something like that behind the z-depth/mist you get some pretty good control over the strength and distance and distance where you want to blur most and least.

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What I wanted is what I asked, it was not for a very precise purpose and the horizon thing was an exemple like mentionned. Having this fully controllable blur material on plane would permit to animate the blur dynamically, change the shape of it easily with shape keys, have full control on it and so for a lot of motion design scenes it would be a great tool for many reasons I think (making just one shape blurry at a moment, blurring the edges of isolated elements without being forced to have the whole background blurry, making a blur motion behind a character / element to simulate a speed trail or heat effect etc etc) . If that’s not possible in Eevee thats unfortunate, still thanks a lot for have tried :slight_smile:

The Z-Depth is great idea too for a distant blur yes, I already used this kind of thing to generate a post prod DOF (after forgot to add it firstly on a very long Cycles render), It worked great. Ty again

Hmm… I think this might be possible with a second View Layer or a second Scene where you render your “blur plane” separately - perhaps with everything besides the plane set to “hold out”.

Confining this type of blur with a certain distance would be possible of course as well. Just combine the blur plane with the z-depth or mist pass in the compositor.
Confining it to a specific object might should be possible by combining it with a cryptomatte pass.

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That 2D logic doesn’t fit well in 3D, what matches the most is to have a transparent material with roughness to emulate a kind of frosted glass.
Anyway, the blurring effect will be different depending on how far object are behind the glass. It will probably not be as smooth and simple a just putting a blur filter in AE.

At some point in blender there will be a viewport compositor that should allow these kind of effects,
in fact it will be like recreating @Lumpengnom solution with AOV but in realtime in the viewport.
And allow to apply some 2D effect to some extend right in the viewport as a post process.

For now I don’t see how this effect could be achievable simply even in other 3D softwares, you need at least to do some post-process compositing on the renders.

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Great options again yes, it’s a bit more tweaky than what would have hoped like having this working in viewport in realtime, but we can’t have all since what I ask is tweaky already haha.
I guess that’s just not possible for the moment. The hold out thing is probably the most accurate and near thing to what I want with some post prod yes, many thanks!

For animation that would have been a smoother process to me since it would for exemple avoid to have either rotoscopy / masking or render multiple layers to then composite in After Effect to apply the blur behind foreground objects. It would basically permit to do every steps in Blender without compositor. I see what you mean yes, i’ll do some tests with tweaked glass shaders but guess i’ll have wait for this kind of things to eventually become possible in Blender.

You could try using a glass bsdf with a high roughness like this:

You can then use the IOR value to change the amount of blur, and use a light path node to remove its shadow.

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Hi,
Thanks you, seemed near to what I want if we get ride off the refraction, but again the thing seems to work only in Cycles (I should had precised in title too that I need it in Eevee)

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You can use a refraction shader instead of glass to get rid of the reflections.
It can work in Eevee but will be very buggy and limited,

Keep in mind that all this is a big hack … maybe not worth in the end !

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I see what you mean yes, anyways I don’t know If i have different Eevee or miss obvious things but even with same settings as you the thing don’t work for me… (not transparent)
I’m gonna give up this idea I think and go for AE VFX when I need this kind of things, everything is not yet possible to do in Blender. ty!

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It looks like the cube is blurred, but probably what’s wrong is that the world color appears around the cube. Be sure to be in rendered view instead of Material Preview. Or change the world color accordingly.

Indeed, that’s also true for other 3D software as well when it comes to do some AE style motion graphics. The opposite is very true, a lot of things are hard or impossible to do in AE that are probably quite easy in blender.

Both software have their own limitations, I found that blur effects and transparency ex : make a text disappear by having all glyph fading out and blurred out one by one are very easy in AE but a big PITA in blender. Once you know the limitations of Blender you can orient the project to take advantage of it. Or stick to AE if it’s really needed.

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