The details of how specularity is defined for DesignWorkshop materials were updated for DesignWorkshop 1.7. This has subtly altered the intrepretation of the specularity field for each material in the "DW Material Prefs" file. The update is backward-compatible, so older "DW Material Prefs" files will work as-is, and old models will still look the same as they did. For future models, the update allows more complete control of specularity values.
There are now two components involved in defining the specularity for a DesignWorkshop material, which we call "smoothness", and "specular reflectivity". To provide for backward compatibility, these two values are packed together into the single overall specularity number.
In general, the smoothness defines how sharply focused a specular highlight will appear (how large or smaller), and the specular reflectivity defines how much of the incident light will be reflected back in the highlight (how bright or dim). In practice, the values interact, so it takes a while to get used to how to adjust them to control particular effects.
To define two components of specularity within one number, the specularity value in the "DW Material Prefs" file is now interpreted as two parts. Four specific digits within the number are interpreted as the smoothness value, and two digits are interpreted as the specular reflectivity.
The smoothness is defined by the 3 digits to the left of the decimal point together with the first digit to the right of the decimal point. For example, if the specularity number in the DW Material Prefs file is 123.456, the smoothness will be 123.4. Smoothness values are exponential, from 000.0 to 999.9. Values greater than about 300 will usually not show a visible difference in renderings.
The specular reflectivity is defined by the second and third digits to the right of the decimal point, and these are interpreted as a decimal fraction. For example, if the specularity number in the DW Material Prefs file is 123.456, the specular reflectivity will be 0.56. Specular reflectivity values are linear, from 0.00 to 0.99, with 0.00 meaning no light reflected into the highlight, and 0.99 meaning 99% of incident light is reflected into the highlight.
The following illustration shows a matrix of spheres rendered in DesignWorkshop with various smoothness and specular reflectivity values.
The spheres on the left have a specular reflectivity of 00.0, and the spheres on the right have a specular reflectivity of 0.99. The spheres at the top have a smoothness of 00.0, and the spheres at the bottom have a smoothness of 100.0.