Emitter behavior Tweet

[kmito]

I'm trying to achieve the halo effect behind a panel located a few inches from a wall by assigning the Octane whiteemitter to the back side surface of the panel facing the wall. For some reason the emitter starts to dim as the panel gets close to the wall. As you can see in the attached image, the bouncing light on the wall is brightest when the panel is 4" from the wall. It start to dim as it gets close to the wall and it turns off completely at 2.75". How do I get the same amount of light emitting from the panel regardless of the distance between the light emitting and receiving surfaces?
Also notice that the floor seems to be getting the same amount of light regardless the wall-to-panel distance except when the light on the wall turns of completely at 2.75" the light on the floor also turns off completely.
Is there a parameter in the settings that controls this emitter behavior?
Thanks,


ArchiCAD 19
Octane Render for AC Release 3.0.1 59
Geforce GTX 780

[face_off]

What Kernel are you using? You should be using the Path Tracing Kernel for this.

Paul

[kmito]

I'm using the Path Tracing. I tried the PMC also but the result was the same.
Thanks,

[face_off]

I don't know the solution - but some ideas to try...

1) Increase the bounces in the PT Kernel (ie. diffuse and specular depth)
2) Reduce the Kernel->Ray Epsilon

If neither of those work - I suggest exporting the scene (twice - one where the halo is there, and one where it is not) to ORBX and posting your question on the Octane Standalone alpha 4 release thread.

Paul

[kmito]

Reducing of the Ray Epsilon has solved the problem!
The smaller the Ray Epsilon the brighter it gets but then moving the panel closer to the wall dims the light again. It's a tricky adjustment as you have 3 different parameters (the emitter power, the emitter to wall distance and the Ray Eplsilon) to control the amount of light.. I really don't understand why the light has to dim and go off as the emitter comes close to the bouncing surface when in the real world the situation is complete opposite.
Thanks so much!

[Daniel_Ward]

Yes, it caught me out for a long time when I couldn't work out why I wasn't getting soft shadows at the base of spheres in my material set up and testing file. (The spheres were 100mm dia and I was getting heavy black shadows under them with the default Ray Epsilon value of 50mm). Generally I find if I set my Ray Epsilon for about 5mm covers me for most of my ArchVis work. Be a little careful of setting it to a value smaller that any typical Architectural cavities you would typically model as otherwise Octane will waste a lot of Rendering Time calculating light bounce inside cavities that won't add anything to your final renders.

Cheers, Dan.

[kmito]

Thanks for the great tip Dan. That's good to know.

Kei