Glass and Transparent Plastics

To create a common glass material, the Refl 90° color can be left at 255 because this glass will not tint the specular reflections. In addition it will reflect almost all light at this viewing angle.

Set the Transmittance color to the color you want the glass to be (255, 255, 255 for pure white glass, or 227, 230, 230 if you want to give it a slight green/ blue tint). Transmittance is set a little low to mimic a low-grade glass with imperfections that give it more color: it is not completely transparent like high-grade optical glass types.

Set the Attenuation distance to 3 cm which is a good value to use for common low-grade glass. Remember from the Transmissive Properties page that Attenuation distance is the distance the light travels through a material before losing half its energy. This means that for a glass panel of 1.5 cm thickness, the light passing through it and reaching the other side will have lost a quarter of its strength. For high-grade glass the Attenuation distance can be much larger – even more than five meters – because it has a lot less impurities which attenuate the light.

Setting a higher Attenuation distance means you will get clearer glass so that it will be easier for light to pass through it.

Set the Nd to 1.51 which is a reasonable Nd for glass. Following the relationship between Nd and the Fresnel effect, we can use the Fresnel formulas to calculate that the reflectance of this material (with an Nd of 1.51) near incidence angle (looking straight on at the material) would be about 4%, which translates into a RGB around 11. This is the value you should use for the Refl 0° color. Of course you do not normally have to calculate this value exactly; just know that for materials with an Nd around 1.5, the Refl 0° color has a value of around 10-20. You can raise it if you want shinier looking glass. If you want to create a very realistic glass, you should look at (images of) real glass objects for references. Most glass materials have an Nd around 1.5.

Remember that Attenuation distance and Transmittance are parameters that work together. For example, you can set a low Transmittance value (such as 220, 210, 200) and start with an Attenuation distance of 3 cm to create a heavily-tinted glass. Raising the Attenuation distance will make the glass clearer. If instead you raise the Transmittance value but leave Attenuation distance at 3 cm, the glass will become less color-tinted but will still be relatively dark.

Roughness must be set to 0 for a perfectly smooth glass. Increase this value (for example to 20) if you want to get a glossy “frosty” glass

The basic structure of a glass material, smooth (Roughness=0) and frosty (Roughness=20). You can download those material examples here: Smooth Glass and Frosted Glass. 

Find more glass examples at the MXM Gallery.