Irradiance White Shadow

[currentstudios]

Having a bit of an issue when attempting to render out an irradiance pass, where this foilage in the planter is casting a white shadow? I've tried changing materials, separating/combining the mesh, and a few other things. Anyone ever see something like this? It's been perplexing me. Beauty and Irradance reference attached.

Thanks

[BK]

Having a bit of an issue when attempting to render out an irradiance pass, where this foilage in the planter is casting a white shadow? I've tried changing materials, separating/combining the mesh, and a few other things. Anyone ever see something like this? It's been perplexing me. Beauty and Irradance reference attached.

Thanks

Hi Currentstudios,

Thank you for the post!!

Would you please share the OFM and Maya versions or DM the scene for us to investigate?

cheers

[currentstudios]

I'm using
Octane 2021.1.5 - 20.19. I've tried both Maya 2020 and 2022.

I tried upgrading to the latest version of Octane, but for some reason it was changing the lighting for the whole scene (mostly environment light not creating shadows anymore). The lighting was client approved, so I had to move back to this version.

Apologies, I'm not sure what OFM stands for haha.

[currentstudios]

Oh thanks!

Further exploring, these artifacts are happening to any mesh in the scene that doesn't have backfaces. This is an environment meant for the web so there are lots of objects that have had un-seen back parts of them cutout to save UV space for lightmap bakes.

Still haven't figured out a great solution though.

[currentstudios]

Yes, I mean meshes with no thickness.

[currentstudios]

Anyone have any reccos?

Another example here, with these books having no faces on the back side, it almost looks like they're emitting light.... Was really hoping to create a light baking pipeline utilizing Octane but this is sorta killing that possibility.

[BK]

Anyone have any reccos?

Another example here, with these books having no faces on the back side, it almost looks like they're emitting light.... Was really hoping to create a light baking pipeline utilizing Octane but this is sorta killing that possibility.

Hi currentstudios,

Thank you so much for the update.

Would you please run the latest stable build and see if it fixes it?
https://render.otoy.com/customerdownloa ... _20.21.exe

If not, is it possible to DM me a trimmed down Maya archive scene?
It would be much faster for us to investigate the scene setup!

cheers

[currentstudios]

Hey BK, gave that a shot, but unfortunately its still the same issue. I ended up going with a less than desirable solution which was to bake lighting maps from a blank white diffuse material. Its unfortunate as the light maps don't have the proper global illumination but oh well.

If anyone wants to look into it for the future, I was able to reproduce this by setting up a simple scene with a cube hovering above a plane, with the bottom face of the cube deleted, and then the daylight environment enabled with irradiance mode turned on.

[roeland]

Hi,

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 1324 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 1324 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 1324 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 1324 times

use-diffuse-detail.png (60.83 KiB) Viewed 1324 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 1324 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.