Why does this message appear?
This warning is triggered when a 3ds Max Falloff map set to Fresnel mode is connected to an IOR slot in a Corona Material, such as the Refraction IOR slot of a Corona Legacy Material. Due to how Corona's internal rendering architecture is built, the specific Fresnel formula used by the 3ds Max Falloff node is not supported in IOR slots.
Why is this setup unnecessary?
While other render engines often rely on Falloff maps to simulate realistic reflectivity - making surfaces less reflective when viewed head-on and more reflective at a grazing angle - Corona calculates this effect automatically. There is no need to manually "fake" this behavior in your materials.
The Recommended Solution
For the easiest and most reliable workflow, we recommend using the Corona Physical Material. It handles these complex reflectivity calculations automatically, delivering physically accurate results right out of the box.
Solutions:
- Remove any Falloff maps set to Fresnel mode from any IOR slots of your materials.
- If you need to map a material's Fresnel IOR based on a texture, you can use:
- The Fresnel IOR slot of the Corona Legacy Material
- The IOR slot of the Corona Physical Material
- The best solution may be switching to the Corona Physical Material which provides better control over a material's IOR, specularity, and metalness.