Thursday, December 20, 2012

Rendering Tip - Transparent Objects

A look at how Index Refraction and Transparency Settings in IRender nXt affect Objects


Recently a user on our forum asked: "I placed a semi-transparent shower curtain in my model, but it rendered like glass. What can I do to fix this?"

The reason semi-transparent, “soft” objects do this is because IRender nXt, by default, treats all transparent objects in SketchUp as glass which reflects light while distorting objects behind the glass. Most transparent objects in SketchUp models are glass, so the default is to render them as such. There would be a similar problem with semi-transparent drapes, or other transparent objects that are not glass.

Though, there are ways to reduce or eliminate this effect by lowering the Index of Refraction to 1.0. (The Index of Refraction determines how much the light and appearance of objects behind the glass are distorted when passing through the glass.) The solution is to right click on the material in SketchUp, load the “Edit Material Wizard” and set the  Index of Refraction for the object to 1.0. (A vacuum is defined as having in Index of Refraction of 1.0)

 More on Glass and Transparency 

There are numerous settings you can make for different kinds of glass. You can view them all at Transparency Settings. Here are a couple of the most important:

Thin and Thick:
  • All glass in the real world has thickness, but often SketchUp modelers will represent it with a single face rather than two faces with a separation or a Rectangular Cuboid. If you create thick glass in SketchUp you should right click on the material and set it to “thick” so you know how to render it properly.
  • Here are two glass objects - One marked, (properly), as “thick”, and the other left as “thin” glass.

 Here are some standard values you can use for other materials:

  • Ice – 1.31 
  • Water – 1.33 
  • Acrylic Glass – 1.49 
  • Flint Glass (Pure) – 1.60 
  • Sapphire – 1.76 
  • Diamond – 2.42 

(See also:  Refraction)


  • Translucency is a form of Transparency where the light passes through a material, but you cannot see through the material. Note in the image that light from the lamp inside the translucent shade illuminates the wall. But the shade itself is not transparent.

See also: Translucency