From 4916f8643457f8c0844fb781fc0728b89077f065 Mon Sep 17 00:00:00 2001 From: Lukas Stockner Date: Tue, 16 Jul 2024 23:54:37 +0200 Subject: [PATCH] Cycles: Expand thin film documentation --- .../render/shader_nodes/shader/principled.rst | 30 +++++++++++++------ 1 file changed, 21 insertions(+), 9 deletions(-) diff --git a/manual/render/shader_nodes/shader/principled.rst b/manual/render/shader_nodes/shader/principled.rst index e4b048cb2..f09555db3 100644 --- a/manual/render/shader_nodes/shader/principled.rst +++ b/manual/render/shader_nodes/shader/principled.rst @@ -347,21 +347,33 @@ Strength Strength from 0.0 to 10.0 -Thin Film ---------- +Thin Film :guilabel:`Cycles Only` +--------------------------------- -Thin Film simulates the effect of iridescence which is the -phenomenon of a surface changing color as the view angle changes. +Thin Film simulates the effect of interference in a thin film sitting on top of the material. +This causes the specular reflection to be colored in a way which strongly depends on the view +angle as well as the film thickness and the index of refraction (:term:`IOR`) of the film and +the material itself. + +This effect is commonly seen on e.g. oil films, soap bubbles or glass coatings. While its +influence is more obvious in specular highlights, it also affects transmission. + +.. note:: + Thin-film interference is currently only applied to dielectric materials. Support for + thin films on top of Metallic is planned in the future. Thickness - The thickness of the film, in nanometers a value of 0 disables the simulation. - For reference the thickness of a colorful looking bubble is about 200 to 500 nanometers. + The thickness of the film in nanometers. A value of 0 disables the simulation. + The interference effect is strongest between roughly 100 and 1000 nanometers, since this is + near the wavelengths of visible light. IOR - Index of refraction (:term:`IOR`) for rays transmitting through the thin film - For most materials, the IOR is between 1.0 (vacuum and air) and 4.0 (germanium). + Index of refraction (:term:`IOR`) of the thin film. + The common range for this value is between 1.0 (vacuum and air) and roughly 2.0, + though some materials can reach higher values. The default value of 1.33 is a good approximation for water. - For reference soap has an IOR of 1.5, so the IOR for a soap bubble should be between 1.33 and 1.5. + Note that when the value is set to 1.0 or to the main IOR of the material, the thin film + effect disappears since the film optically blends into the air or the material. Outputs -- 2.30.2