The method in the paper yields #iridescence that resolves to a plain reflection for thicker films, like in daily life. My nodes suffer from spectral aliasing, which means the colors keep cycling no matter the film thickness.

Now, we can have absorbing films while keeping the look and behavior of thick films. The render shows the nodes on the left and the native behavior on the right. The native behavior more accurately reflects the real-world experience.
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#blender3d #thinfilminterference