Redshift & Cinema4D | Improve your interior lighting with Portal Lights

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When lighting interiors, we often use environment maps to create a natural look. The only issue is that this requires a lot of global illumination bounces to look good and can significantly increase render times.
We can avoid adding GI bounces by using portal lights instead.
Portal Lights act as a virtual window, casting direct lighting into a room from the environment outside.
They effectively give you one bounce of 'brute force' Global Illumination for 'free'.
It works by sampling light color from the environment map shader, or the custom 'Environment Shader' parameter in the portal light.
To add your environment map shader to your scene open the render settings and under the redshift globals tab drag the shader into the Default Environment field.
I placed two portal lights in this scene, one above the skylight and another just outside of the archways to the right of my camera.
You can see in the before and after images that the portal lights added a lot of soft, warm, natural lighting to the scene.
The portal lights will only work if there’s an environment map selected in the render settings or a domelight in the scene.
In this example, I’ve turned off my domelight and removed the environment shader from the render settings. Now when I turn on my render view there’s no lighting.
I used a domelight for the initial setup of this scene but found that turning the domelight off and adding an environment map in the render settings could deliver some really interesting looks from the portal lights.
Alright, that was a brief overview on portal lights and their benefits when it comes to lighting interiors.
If you found this video helpful throw me a like down below. I’ll see you in the next tutorial.

[@michaelansah]

Very useful and concise. Thank you!

[@the-astropath]

Appreciate that!

[@shehranamin005]

actually a very great one

[@the-astropath]

Thank you :)

[@arseniyzibarev8788]

thamks bro!

[@the-astropath]

[@derekheisler2058]

Portal lights work great when the window is flat. But what would one do when there's a curved or complex window, like for example a car window or windshield. I'm still looking for a solid solution for portal lights and car interiors but haven't cracked it yet. Thoughts?

[@the-astropath]

Honestly I'm not sure. My first instinct would be to just increase the size of the portal light to compensate for the curve. Or use multiple portal lights and tilt them accordingly.

[@derekheisler2058]

They really should allow portal lights to mesh like area lights do. Select the geo for the windows and you’re set.

[@yannistath]

Portal light is unnatural and causes problems in general. You have to do what you would do in real life pumb you shutter speed in your camera and your ISOs. So on you IPR window settings under the photographic exposure, bump your film speed (iso) and shutter time ratio, this will bring the light in your scene naturally

[@the-astropath]

@@yannistath Portal lights are more about making your scene more render efficient and less about making things physically accurate like you're describing.