Rendering Question - Transparent 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?"


This is because IRender nXt, by default, treats all transparent objects in SketchUp as glass which reflects light and distorts objects behind the glass.

Most transparent objects in SketchUp models are glass, so the default is to render them as if they were glass.

You would have a similar problem with semi-transparent drapes, or other transparent objects which were not glass.

You can reduce or eliminate this effect by lowering the Index of Refraction to 1.0

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.

Transparency tab.jpg

More on Glass and Transparency

As you can see from the Wizard above there are a number of settings you can set for glass. You can view them all at Transparency Settings . But here are a couple of the most important.

  • Thin and Thick
All glass in the real world has thickness, but often 3D modellers will represent it with a single face rather than two faces with a separation or a Rectangular Cuboid. If you create thick glass, with 2 (o4 6) faces per pane, you should right click on the material and set it to Thick so we know how to render it properly.
Here are two glass objects - the one on the left is marked, (properly), as Thick, and the one on the right left as thin glass.
The left, Thick, one has refraction from the thick glass.
The right, Thin, one treats the edges of the solid object as individual pieces of thin glass.
  • If you use a single face to create a window pane, it should be marked as thin.
  • If you use two faces for a single window pane, it should be marked as thick.
  • If you create a solid object, such as the cube below, it should be marked as thick.

  • Index of Refraction
The Index of Refraction determines how much the light and appearance of objects behind the glass is distorted when passing through the glass.
A vacuum is defined as having an Index of Refraction of 1.00
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
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.

" Transluceny.png

See also: Translucency

See also