Use the Library > Rendergraph > Presets > Glass preset from the library to render convincing glass objects. This preset uses the Surface2 shader and overrides specific parameters to avoid classic caveats.

4 bounces refraction on a hollow glass.

By default, the Glass preset forces a 4 bounces refraction so it is easy to render a transparent glass. You can easily change this to a 2 bounces refraction by modifying the following attributes:

  • Shader > Spec1 > Ray Depth = 2
  • Shader > Glass > Ray Depth = 2
  • Attributes > Raytracing > Max Bounces = 1

The Max Bounces value makes sure the glass object won't be traced any more after 1 bounce.

The Stanford Armadillo rendered with 2 bounces, and with 4 bounces. The Library/Materials/Surface shader for details.

Rendering glass using a large number of bounces and russian roulette enabled makes it generally easier to produce convincing images without dealing with the usual energy loss problems.

Double Sided Glass

Use Double Sided mode to render classic, plain glass objects. This model fully simulate refraction and the appropriate deviation of light crossing the surface.

Varying Spec1 and Glass Roughness = 0.0, 0.2 and 0.4.

Thin Glass

Use Thin Glass mode to render thin layers of glass, such as windows. This model approximate a thin layer of glass, and allows rough surfaces.

Enclosing the Armadillo inside a cube made of Thin Glass.

Varying Spec1 and Glass Roughness = 0.0, 0.1 and 0.2.

Transparency Glass

Use Transparent Glass mode to render thin layers of smooth glass, such as soap bubbles. This model uses transparency (as implied by its name) to simulate thin refractions, and doesn't consider successive layers of transparency as refractions, thus not requiring to increase the number of refraction bounces.

A soapy Armadillo bubble using Transparent Glass and Iridescence.


Caustics caused by glass objects are generally expensive to render, but can be simply approximated with the Surface2 shader. Set the Glass > Caustics to Fake to render the glass with transparent shadows, or to Real to render the real shadows.

Rendering the Glass Armadilla, faking caustics, with caustics blurred at 0.2 and 0.05.

Real caustics aspect are affected also by the RenderPass Render Settings > Caustics > Caustic Blur and by the Render Settings > Pixel Filter > Clamp Pre Filter parameters.