Filament emitting light from inside glass bulb - best settings?

[futoryan]

Hey everyone,

I'm trying to get the filament of a light bulb to emit enough light to be noticeable but balanced in my scene.

I'm currently rendering with pmc but I don't know how to optimize the kernel for a render of this type. Which settings would be best to tweak to get the most out of the render?

I've attached a screenshot with my current setup. I'm using the most current version of Octane, 2.16.

Does the blackbody emitter on the filament material need to be configured differently because it's a small light source? I'm struggling to understand the balance between the power and efficiency settings.

Thanks for the help! I really appreciate it.

Best,
Dmitry

[aoktar]

try PT kernel for faster renderings if you don'T need caustics. Set "gi_clamp" low as 1 or around this. caustic_blur=1, coherent ratio=0.3-1. Test and read this parameters to understand how speedups. Use "fake shadows" on materials of bulbs.

[futoryan]

try PT kernel for faster renderings if you don'T need caustics. Set "gi_clamp" low as 1 or around this. caustic_blur=1, coherent ratio=0.3-1. Test and read this parameters to understand how speedups. Use "fake shadows" on materials of bulbs.

Thank you aoktar. I'm rendering now with the settings you suggested. Can you clarify how fake shadows in the specular material works with this scene? I'm noticing that it's letting a lot more light escape through the glass than when I had it turned off. Is it behaving more like a light portal material now?

Regarding the settings for the blackbody emission in the filament material, if I wanted to turn down the brightness of the material itself but have it emit the same amount of light, are there settings to control that independently? Similar to the Illumination settings in the standard C4D materials?

Illumination.png (31.9 KiB) Viewed 5091 times

I'm trying to get the filament to appear more like this:
http://www.viesso.com/media/catalog/pro ... s-base.jpg

Thanks again for all your help!

[FooZe]

Fake shadows lets all light through and only takes into consideration the transmission value and fresnel effect of the glass.
It will not do a proper calculation of the lights path based off the IOR of the glass or anything like that. So there won't be any pretty patterns like this: http://upload.wikimedia.org/wikipedia/c ... austik.jpg

It helps octane to do lighting through glass by simplifying calculations.
Otherwise all the light will be very accurately simulated on it's journey through the glass which can take some time to become noise free.

In octane the brightness of the emitter is directly tied to the power of it, so you can't change them independently.

It looks like the brightness of the filaments in your reference shot are very low and is not what is lighting the scene in general.
You could add a light source with opacity 0 (invisible) to control the lighting independently of the filaments power.

[futoryan]

Thanks for your excellent explanation FooZe!

It didn't occur to me to put an a light inside the bulb and make it invisible. Since Octane doesn't use Omni lights, would you use an area light or an IES light to do that?

[FooZe]

Just use a cube or low poly sphere and then apply a diffuse material with an emission and make the opacity zero.