hi all,

from optics class: R = { (N-1)/(N+1) }^2 for reflection coeff R and refraction coeff N, also known as the IOR.

the inverse: N = [1+sqrt(R)] / [1-sqrt(R)]

for water, N=1,33 resulting in R = (0,33/2,33)^2 = 0,02 - it hardly reflects at all.
for glass, N=1,50 resulting in R= (0,5/2,5)^2 = 0,04 - twice as reflective

for gold, say R = 0,90 resulting in N = (1+0,95)/(1-0,95) = 39.
for silver, say R=0,95 resulting in N=79
for pewter say R=0,70 resulting in N=12

of course one can take the complex arithmatic route to be exact but I guess Poser Fresnel is not supporting that.

Also note: considering reflections on a ball the R gives the reflection in the middle area while fresnel takes it to 100% at the edges. For R=2% (water) this is far more noticeable than for R=95% (silver) already.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

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