Forums Technical Discussion Emissive shader and lighting

Emissive shader and lighting

   4550   7   0
User Avatar
Island
Member
340 posts
Joined: June 2017
Offline
 
I am trying to have an emissive shader contribute to light and shadows but it doesn't appear to do so. What am I doing wrong? Thanks.
Edited by Island - Sept. 7, 2018 21:46:59

Attachments:
Softbox.hiplc (545.8 KB)

 Report
User Avatar
jsmack
Member
7737 posts
Joined: Sept. 2011
Offline
 
Before looking at your scene, the first thing that comes to mind is do you have diffuse bounces?
 Report
User Avatar
Island
Member
340 posts
Joined: June 2017
Offline
 
I don't think I have any diffuse bounces. They only way to make the above file actually work that I can see is to add a geolight and pick the softbox. I'm not sure why that is necessary, as the light emission shader is set to light objects.
Edited by Island - Sept. 7, 2018 22:14:01

Attachments:
HoudiniSoftlight.jpg (126.8 KB)

 Report
User Avatar
tamte
Member
8518 posts
Joined: July 2007
Online
 
as mentioned before to make pure emissive material light your scene, set diffuse bounce limit on Mantra to at least 1

so while geolight is not necessary, it is still advised to use it in your case as if will provide better sampling than just pure emissive material
Tomas Slancik
FX Supervisor
Method Studios, NY
 Report
User Avatar
Island
Member
340 posts
Joined: June 2017
Offline
 
Thank you for the suggestions. I added those and the shadows look better, but the render times are awful and there are strange artifacts on objects with a principled shader. I'm not sure what is going on, but it is probably user error.
Edited by Island - Sept. 8, 2018 14:25:33

Attachments:
Softbox.hiplc (764.4 KB)
HoudiniSoftbox.jpg (352.9 KB)

 Report
User Avatar
Island
Member
340 posts
Joined: June 2017
Offline
 
Any idea about the artifacts? Thanks.
 Report
User Avatar
tamte
Member
8518 posts
Joined: July 2007
Online
 
you are rendering your softbox objects also using them as lights so they are shadowing themselves causing your artifacts
so either don't include them in render and make your geolights renderable or remove them from shadow casting

also instead of geolights can youmaybe use area lights with texture, if your only purpose is to emulate softbox?
Edited by tamte - Sept. 8, 2018 16:59:20
Tomas Slancik
FX Supervisor
Method Studios, NY
 Report
User Avatar
Island
Member
340 posts
Joined: June 2017
Offline
 
The reasons for using a softbox rather than area light are:

1. ability to control direction and angle of light
2. to better replicate reflections in a studio environment.

Maybe I can replace the geolights with an area light approximately the size of the emissive portion of the softbox and make it a child of the softboxes. I'll try that to see if it works better.

Interestingly, it appears with making a geolight from an object, it uses the materials on the object and doesn't light in the direction that the portions of the object are shaded black.
 Report
  • Quick Links