Glowing object on Arnold


#1

Hi everyone, before we start i want to say i allready tryed several tutorials involving the emission attribute and the mesh light for Arnold but they all have something in common: you can only tell the object is emiting light because it reflects it on other objects.
So if there is a plane near you see the light reflected on it, but what if you want to make a neon light, with a halo around it, like a light saber?
Every tutorial i saw uses the same two methods but so far i was not able to make the halo effect.

Something like this:


#2

You need some kind of volume scattering to get the glow effect, for example:

https://support.solidangle.com/display/A5AFMUG/Atmosphere+Volume

Also on this page if you scroll down to the bottom, they’ve made a light saber beam with just a spotlight which is a pretty interesting approach:

https://support.solidangle.com/display/A5AFMUG/Spot+Light


#3

Well, the spot light was interesting, still working on a way to manipulate it at will.
The mesh light, on the other hand, is terrible. I´m getting a very pixelated light.
I tryed pumping up the sample values of the mesh light but it changed nothing. I tryed pumping up the sample values of the volume scattering and even on a value of 100 (wich took way too long to render) i still got black dots on the mesh light.

What you see here is a volume scatering with density of 1, attenuation 0, anisantropy of 0.9 and 10 sample value. Like i said, 100 sample value did improved the image but it took too long and still got a black dots on the center.


#4

Yes mesh lights produce severe noise with volume scattering, SA even has a little disclaimer about it on the mesh light page. You might have to use extremely high AA (I’m talking like 12+) on top of the maxed out atmosphere node samples for it to start to look clean.

If you’re going to render glow from a mesh light, it’s going to be expensive. You’re probably better off adding it in post.


#5

Maybe you are right. I wonder how they did this image, though. I tryed using a point light but it´s too small. I might have to just go for post.


#6

My guess is they used a polysphere with an emissive shader and set the geo to not cast shadows. Then they stuck a point light inside for the actual lighting.

Here’s a test using that method, 10 samples in the volume node and 4 AA, 3 samples on the point light, render time 19s. There is indirect noise still but the scattering is clean.

There are quite a few possibilities using this strategy with the different lights and filters, it does have its limitations though.


#7

That was really helpfull, i managed to get something similar to that.
Thanks a lot for your patience and help.