Thanks to the help of Micheus, light portals are now working in the YafaRay plug-in. I have updated the file for the unofficial plug-in on my website.
The light portal object needs to be created by extracting a face from a cube or other object using the "extract" face command. Light photons will emit in the "Normal" direction of the face that has been extracted. If you need the light photons to emit in a different direction simply rotate the extracted face.
Here are two examples. One with a low power setting and one with a high power setting. The power setting in the Ambient/HDRI is set very low in both examples so that most of the light comes from the light portal instead of the ambient light. Samples is also set to only 64 in the Ambient/HDRI light to avoid longer render times. The Samples setting in the light portal material has a big impact in reducing graininess without a big impact on render time. Samples is set to 480 in both example renders. A power of 4000 was used in the second image.
oort
Low Power Light Portal
High Power Light Portal
The light portal object needs to be created by extracting a face from a cube or other object using the "extract" face command. Light photons will emit in the "Normal" direction of the face that has been extracted. If you need the light photons to emit in a different direction simply rotate the extracted face.
Here are two examples. One with a low power setting and one with a high power setting. The power setting in the Ambient/HDRI is set very low in both examples so that most of the light comes from the light portal instead of the ambient light. Samples is also set to only 64 in the Ambient/HDRI light to avoid longer render times. The Samples setting in the light portal material has a big impact in reducing graininess without a big impact on render time. Samples is set to 480 in both example renders. A power of 4000 was used in the second image.
oort
Low Power Light Portal
High Power Light Portal