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<PRE>Hi Lars,</PRE><PRE>Just wondering, do you have a roughness value (RMS) or equivalent from the manufacturer?</PRE><PRE>If not, could it be possible that the 60-degree measurement is used to define the roughness value? The higher value (82) seems like a way to define the BRDF.</PRE><PRE>i.e. BRDF(theta-i, phi-i, theta-r, phi-r) = 82/76 = 1.079</PRE><PRE>You'd need to know (manufacturer definition)what the actual angle configurations (theta and phi) are for the 60-degree measurement, then working backwards using the Radiance equation, you'd get the roughness (RMS) value.</PRE><PRE>for example, if both angles are zero, roughness = 0.272.</PRE><PRE>if both angles are 30 (60-degree split evenly), roughness = 0.292</PRE><PRE> </PRE><PRE>What exactly is the material? If it is more smooth than rough (polished metal rather than plastic-ky) then obviously my guess is wrong.</PRE><PRE> </PRE><PRE>cheers,</PRE><PRE>YC Huang</PRE><PRE> </PRE><PRE> </PRE><PRE>I thi!
nk that what you want to do is:
<total reflectance> - <diffuse reflectance> = <specular reflectance>
thus
86 - 10 = 76
The specular reflectance that is provided is for a measurement at 60
degrees incidence, if I understand this correctly.
-Jack
Lars O. Grobe wrote:
><I> Hi,
</I>><I>
</I>><I> as this may be because of some standards that I am not aware of, I
</I>><I> have a question about a record of material properties that I do not
</I>><I> understand yet.
</I>><I>
</I>><I> I have a high reflective surface, and the manufacturer gives me these:
</I>><I>
</I>><I> reflectance specular 60 degree: 82
</I>><I> reflectance diffuse: 10
</I>><I> reflectance total (ASTM E1651): 86
</I>><I>
</I>><I> If I add 82 and 10 I get 92 > 86 for the total reflectance. So what
</I>><I> does this mean, are the values related to the way the reflectance is
</I>><I> measured and calculated using different procedures according to
</I>><I> standards?
</I>><I>
</I>><I> CU Lars.
</I></PRE>
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