How to Use Transmission for Glass in Blender

This guide provides a straightforward tutorial on using the Transmission property in Blender's Principled BSDF shader to create realistic glass materials. You will learn how to adjust essential parameters such as Transmission, Roughness, and Index of Refraction (IOR), as well as the specific settings required to render transparency properly in both the Cycles and Eevee render engines.

Step 1: Apply the Principled BSDF Shader

  1. Select your target mesh in the 3D Viewport.
  2. Navigate to the Material Properties tab (the red sphere icon) on the right panel and click New to create a material.
  3. Ensure the surface shader is set to Principled BSDF.

Step 2: Adjust Core Glass Parameters

Locate the following sliders in the Principled BSDF material settings:

  • Transmission: Increase this value from 0.0 to 1.0. This turns the material fully transparent, allowing light to pass through the object.
  • Roughness: Controls the clarity of the glass.
    • Set to 0.0 for perfectly clear, smooth glass.
    • Increase slightly (e.g., 0.1 to 0.3) for frosted or matte glass.
  • IOR (Index of Refraction): Controls how light bends when passing through the material.
    • Standard glass typically uses an IOR of 1.450 to 1.520.
    • Water uses an IOR of 1.333, while diamond uses 2.417.
  • Base Color: Set to pure white (#FFFFFF) for clear glass. Change the color if you want tinted glass (e.g., green or blue bottle glass).

Step 3: Configure Render Engines

Depending on whether you are using Cycles or Eevee, additional steps are required to display transmission correctly.

Rendering in Cycles (Ray Tracing)

Cycles handles light transmission automatically. However, to ensure clean renders without dark artifacts:

  1. Go to the Render Properties tab.
  2. Expand the Light Paths dropdown, then expand Max Bounces.
  3. Ensure Transmission bounces are set to at least 8 or 12 so light can pass through multiple stacked glass objects.

Rendering in Eevee (Real-Time)

Eevee requires specific settings to process refractions in real time.

  1. Enable Screen Space Refraction globally:
    • Go to the Render Properties tab.
    • Check the box for Screen Space Reflections.
    • Expand the Screen Space Reflections tab and check Refraction.
  2. Enable Refraction on the Material:
    • Go to the Material Properties tab for your glass object.
    • Scroll down to the Settings section.
    • Check the box for Screen Space Refraction.
    • Set Blend Mode to Opaque or Alpha Hash depending on your shadow preference.