Is there a need for portal materials?

[dermotfaloon]

I am a recent C4D Octane user and when lighting internal spaces through a window etc it is advised to use portal materials etc.
Has this changed as the glass with fake shadows seems to work just fine, I cant see the difference?
Am I missing something or is there now no real use for Portal materials.

[paride4331]

Hi dermotfaloon,
please refer to:
https://docs.otoy.com/StandaloneH/Stand ... ght=portal
https://docs.otoy.com/Cinema4DH/C4DPlug ... ght=portal
I hope it will help you.
Regards
Paride

[bepeg4d]

Hi dermotfaloon,
Portal material acts differently in Octane, compared with other render engine.
While normaly it is used to bring more light through an aperture, in Octane is used to help the kernel to find the Environment in scenes where the openings are very small, compared with the entire closed room, in this way, the paths are able to end their travel.
To obtain a similar effect as the classic Portal material, it is possible to create a plane in the opening facing the room, slightly smaller and without intersection, just above the window/opening, with a Diffuse emissive material, and 0 opacity.
In this way, you can mimic more efficiently the extra light that comes from the sky through the opening with diffuse light, and the image is cleaned much faster.
ciao beppe

[dermotfaloon]

Thanks for the reply, so is there an ideal setup for glass windows in something like a bus etc.
I cants see the difference between a portal setup and some fake planes infront for reflections Vs basic glass materials with fake shadows enabled.
I may need to experiment more to get the best from this.

Regards

[enricocerica]

Thanks for the reply, so is there an ideal setup for glass windows in something like a bus etc.
I cants see the difference between a portal setup and some fake planes infront for reflections Vs basic glass materials with fake shadows enabled.
I may need to experiment more to get the best from this.

Regards

Portal, like emit plane with opacity set to 0 used in a room scene are not visible and are not intended to be visible. Portal is used to help the render engine to bring light in poor illumination regions of the scene, emit plane with opacity = 0 is used to increase the global illumination of the room and create fake entering light, that's the reason why we put them in front of windows, mainly to give the illusion that light is entering from the window but you may of course place them anywhere in the room, after all it's just a mesh light.