Can you confirm if the white areas become transparent if you enable the alpha channel?
In irradiance mode, areas where shadow rays reach backfacing polygons are made transparent. This avoids black edges where objects intersect the ground.
If this peculiar behaviour is a problem in your scene, Octane also supports a mode where this doesn’t happen: switch off ‘Irradiance mode’ in the kernel settings. Open the render passes node and add or enable the ‘Irradiance’ pass. This has the same behaviour as baking a white diffuse material, however it outputs irradiance directly so you don’t have to edit the material.
If you consider the floor on this simple example:
- scene.png (195.57 KiB) Viewed 759 times
If using a white diffuse material, you will see that the area inside the round yellow thing is black since no light reaches inside it.
- bake-diffuse.png (33.58 KiB) Viewed 759 times
In irradiance mode the area will become transparent. But the plane is only a single polygon with normals facing upwards, so the area under that also becomes transparent.
- bake-irradiance.png (36.6 KiB) Viewed 759 times
This leads to different artefacts when using the baked images:
If using the one from the white diffuse material, you often get visible black edges around objects. Depending on how high resolution the baked irradiance is, these can be quite visible.
- use-diffuse.png (697.64 KiB) Viewed 759 times
- use-diffuse-detail.png (60.83 KiB) Viewed 759 times
While the irradiance mode doesn’t work if you have single sided polygons in the scene. However there will be no black edges around objects.
- use-irradiance.png (687.98 KiB) Viewed 759 times
So which mode works best can depend on your scene, and how much resolution you’re able to have for your baked irradiance maps.
