Arrow Group Industries LM86 Bedienungsanleitung PDF herunterladen (Seite 127)

Maxwell Render 2.5 User Manual

Chapter 14. Appendix I. Materials Examples | 127

e. Example 5: Common glass

To create a common glass material, the Re 90° color can be left at 255 because this glass

will not tint the specular reections. In addition it will reect almost 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.

Fig.01 Low grade glass by Mihaii Fig. 02 subtle Sandblasted glass by jomaga

Set the Attenuation distance to 3 cm which is a good value to use for common low-grade

glass. Remember from the material section 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 ve 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 reectance

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 Re 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 Re 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.

More glass examples at the MXM Gallery

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Arrow Group Industries LM86 Bedienungsanleitung Seite 127