question

kenny chang avatar image
kenny chang asked ·

Disabling the specular visibility of light

Is there a way to disable the specular/transmission visibility of an analytic light aside from turning off the spec/trans contribution or light-linking?

For example, I would like to have a quad light not be visible in a mirror but still have specular contribution. I understand that the specular reflection of a light is part of it's specular contribution but I was hoping there's a workaround, similar to how trace sets work with geometry.

I've tried:

1. Turning off specular contribution, but it turns specular rays completely off, not just the visibility of the light in the reflection.

2. Using light-linking, which again effectively disconnects the light from the mirror

3. Trace sets: do not seem to work with lights, only geometry.

4. One workaround is using mesh lights and creating a trace set with the geometry and add it to the trace set for the mirror.

(On a similar topic, mesh light does not have transmission contribution attribute, is this intentional?)


I want to avoid rendering multiple passes and/or compositing as well as using LPE's.


Any details on how best to go about setting this up would be great.

Thanks,

Kenny

lightrayswitch
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

kenny chang avatar image
kenny chang answered ·

Hi Lee,

Just want to get clarification if the aiRaySwitch limitation for lights is the expected behavior?

The aiRaySwitch with a skydome only the camera and shadow rays work.

The aiRaySwitch with a quad light only the camera ray works and the light emission is effectively killed.

Thanks,
Kenny

3 comments Share
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

I don't know how you are using it? Can you post screenshots or even better a simple scene somewhere?

0 Likes 0 · ·

Hi Lee,

Attached is a simple scene with a quad light with a texture mapped to it. The texture is fed through the aiRaySwitch before connecting to the color parameter of the light.

lightsWithRaySwitch.zip

Ref image 1

Default setup without aiRaySwitch

Ref Image 2

With aiRaySwitch, the camera ray for the quad light is working, but the shadow ray doesn't, and the light contribution is effectively killed.

0 Likes 0 · ·
selection-022.png (553.4 KiB)
selection-023.png (173.4 KiB)

Hi Kenny, this from the backroom boys:

"because of the way the sampler works, it can't assume that the shading will change depending on how the light is being viewed. if he wants the light to be invisible to specular, there are visibility controls for that on the light itself".

0 Likes 0 · ·
Lee Griggs avatar image
Lee Griggs answered ·

Have you tried the ray_switch shader? Also, why are you doing this?

1 comment Share
10 |600 characters needed characters left characters exceeded

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Hi Lee,

I need a light emitting a lamp without seeing the light in the reflection. Ideally an analytic light would be preferable over a mesh light.

I should have mentioned that I tried the aiRaySwitch with lights. Here are the results:

1. Skydome with aiRaySwitch: works with camera and shadow rays only.

2. Analytic lights with aiRaySwitch: works with camera ray only, but light emission is killed.

Is this the proper workflow for using aiRaySwitch with lights? If so, are these the limitation/expected behavior?

Best,

Kenny

Specs: Linux Centos 7, Maya 2018.5, MtoA 4.0.1 Arnold Core 6.0.1.0

0 Likes 0 · ·

Write an Answer

Hint: Notify or tag a user in this post by typing @username.

Up to 5 attachments (including images) can be used with a maximum of 2.0 MiB each and 9.8 MiB total.

Welcome to the Arnold Answers community.

This is the place for Arnold renderer users everywhere to ask and answer rendering questions, and share knowledge about using Arnold, Arnold plugins, workflows and developing tools with Arnold.

If you are a new user to Arnold Answers, please first check out our FAQ and User Guide for more information.

When posting questions, please be sure to select the appropriate Space for your Arnold plugin and include the plugin version you are using.

Please include images, scene and log files whenever possible as this helps the community answer your questions.

Instructions for generating full verbosity log files are available for MtoA, MaxtoA, C4DtoA, HtoA, KtoA, and Kick.

If you are looking for Arnold Documentation and Support please visit the Arnold Support site.

To try Arnold please visit the Arnold Trial page.

Bottom No panel present for this section.