I am trying to create an LED wall effect for a background in Cinema4D and trying to make the individual LED lights shine convincingly. I made the LED material that displays the texture from an image giving it these settings:

Glow and Luminance material settings

The result wasn't so great:

first result

So after having watched this LED light show video I added the Glow setting in the Render Options as follows:

Glow Render Option settings

and achieved this result that is pretty much what I need at the moment:

Successful glow effect, could be made brighter

However, this had the undesired consequence that any and all lights and or backgrounds also have the Glow applied to them in the render as follows:

Undesired glow and blur everywhere!

Is there a way to have the glow effect only apply to the glowing material? OR, is there a better way to achieve this glow effect I could look into? (I am pretty new to C4D).

If you wish to have a play around with the original files I have uploaded them to my GDrive Zipped here.

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    In the tutorial the leds are the only elements in the scene. You might have to render your light objects separately from the rest. – Luciano Sep 10 '19 at 9:51
  • Hi @Luciano, thank you for your input. Indeed you are right about the video, being new I thought glow in render applied to glow effects. Do you mean that I only render the LED objects, then do a second render with everything else, then layer the LED onto the image with like photoshop? – Fiztban Sep 10 '19 at 10:07
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    Yup, it's a quick-and-dirty for now. But I'm hoping someone more knowledgeable in C4D will come up with an answer with a better way to do this. – Luciano Sep 10 '19 at 10:21
  • I can try it out, thank you. I also hope someone who knows more about the renderer will also drop some knowledge on us. – Fiztban Sep 10 '19 at 10:38

A literal and correct answer to your question is, "No. C4D render effects are inherently whole-scene," but since there are a bunch of alternative methods that will work, what we're actually dealing with here is an instance of the XY problem. Rather than tell us how you want the problem solved, tell us what the problem is and what "success" looks like, so we can instead advise you on the best way to get from point A to point B.

The way I used when I last had to do something similar is to use the old "Glow" effect on the LED materials:

glow channel on material

I characterize that as an "old" method not only because it goes way back in C4D's history — I don't think I remember a time when it wasn't there, and I go back to R8.5 — but also because it's an unrealistic cheat. It's basically the same render effect you're using now, only applied to a particular material.

This is why you won't find a "glow" effect in C4D's new Uber Materials nor in the underlying node-based material system added in R20. These materials are physically-based, so they're trying hard not to cheat. They pair well with a physically-accurate renderer such as C4D's Physical Render.

When you see an LED glow in real life, one of several things is happening:

  1. You're seeing the light through an imperfect lens, which is exhibiting flare. Flare isn't limited to the spectacular effect you see in JJ Abrams films: it can be a subtle glow around bright objects due to light bouncing around in the lens instead of going straight through. The more light, the more flare, so it appears as though flare is affecting only the bright lights in the scene, but since it's a non-ideality in the lens design, it actually affects all light passing through it.

    C4D has a few related settings to this effect in its physical sun object and in its Lens Effects setting on other light objects, but I don't see a way to make this apply to other light emitters in the scene.

    There is probably third-party software that will look at the bright areas in your scene and apply such effects to them. For this to work best, you'll probably want to render out to an HDRI format so you can target the glow effect properly.

  2. The glow is lighting up something nearby. If that's the effect you want, then the problem is either:

    • You aren't using GI so that the Luminance or Emission channel of your material can light up the scene, thus painting surrounding areas with its color.

    • Your surrounding objects' materials aren't able to reflect that light properly. This is usually caused by using non-physical material types which have fakes for color handling like the Diffuse channel, whereas physically-accurate materials do this with the Reflection channel, allowing incoming light to be absorbed and reflected properly.

  3. The glow is lighting up the surrounding material through the material. This is modeled with subsurface scattering in C4D. If the LED is embedded into a milky white carrier, for instance, this is almost certainly what is happening, not a fake "glow" post effect.

  4. The air isn't clear, so the LED is lighting up the fog, smoke, or dust in the air. So, add smoke, fog, etc. to your scene in C4D.

Sometimes you get to split the difference. The older PBR material type in C4D is physically-based, but there is a Glow effect on it. Shrug. It's a cheat, but if you want it, there it is.

Maybe you want to use physically accurate materials and renderers, but you still want to cheat the glow effect. Simply set up an object buffer for the LEDs, then render that object buffer out as a separate pass, and add the glow effect using that as a mask in post. There are many photo editors, video editors, compositors, and other tools that can do this: Photoshop, After Effects, most high-end video editing packages, all high-end compositors...

Here's how you'd do it in Davinci Fusion, the compositor now bundled with the free version of Davinci Resolve, a high-end video editing package:

Fusion node setup

The top node is the object buffer for the LEDs in my scene, rendered by C4D as a separate grayscale image, then converted to RGB to placate Fusion. I then apply a glow effect to it, darken it so it doesn't overpower the next steps, then lighten only the red channel, giving a colorize effect. Here's the result of those steps:

7-segment LED glow only

Finally, I screen that over the top of the base render in the Merge node you see at the center of this setup, with this result:

7-segment glowing LED render

Voilà, a glowing 7-segment LED display, rendered with physically-accurate Uber materials using C4D's Physical Render feature. Despite lacking a Glow channel on my material and having a wish for the whole scene not to glow, I was able to use a compositor and C4D's multipass rendering to get the effect I wanted.

You could do essentially the same thing in many other programs.

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  • Warren, I would like to take the time to say I truly appreciate your full response, for someone like me just starting it has been most enlightening from a meta perspective as well as practical. I had used 3ds Max and had learned to work with nodes there, even after doing a couple C4D courses I didn't realise a similar system was actually already in R20! You are right about how I explained my problem. I was much too focused on what I wanted and how what I was doing wasn't creating the effect I have experienced of an LED wall i.e. high brightness with accurate colour. – Fiztban Sep 16 '19 at 8:24

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