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Mastering Translucent Materials: Glass and Liquid Rendering

Published April 2026 · Estimated read: 7 min read

Rendering glass and liquids effectively is often the ultimate test of a 3D artist's technical prowess, as it forces the render engine to calculate immensely complex photon behavior.

The Physics of the Index of Refraction (IOR)

Correct glass rendering begins with assigning the exact physical Index of Refraction (IOR) to the shader geometry. Standard crown glass sits at 1.52, while water is 1.33. Nailing these precise physical values guarantees that background shapes distort accurately behind the geometry.

The Liquid Meniscus and Intersecting Geometry

A common amateur mistake is leaving an air gap between the liquid mesh and the glass container mesh. In reality, liquid adheres slightly to the edges of glass (the meniscus) and directly touches the container walls. To render this accurately, the liquid mesh must physically intersect the glass geometry slightly, and the IOR of the intersection must be calculated properly.

Sub-Surface Scattering in Colloidal Fluids

If the liquid isn't pure water—such as milk, juice, or thick cosmetics—pure transmission isn't enough. Sub-Surface Scattering (SSS) must be dialed in to replicate how light enters the liquid, bounces off suspended organic particles, and exits at a different angle, giving the fluid a cloudy, full-bodied realism.

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