Hi Frank, I wish VSL would use the more familiar Refraction Index instead of this 'optical thickness'.
Conversion: Refraction Index = 1 / (1-optical thickness) or optical thickness = 1 - 1/refraction index I found a table with refraction index values for several substances (for yellow light): fluorite: index 1.43 -> thickness 0.3 canada balsam: 1.53 -> 0.346 salt 1.54 -> 0.351 diamond 2.42 -> 0.587 flint glass (light) 1.51 -> 0.338 flint glass (heavy) 1.65 -> 0.394 crown glass (light) 1.51 -> 0.338 crown glass (heavy) 1.61 -> 0.379 ice 1.31 -> 0.237 water 1.33 -> 0.248 So, your values are OK. However, in the test scene I found that there was no total reflection in the prism with values around 0.33, so I just increased optical thickness until I got it. Never mind theory, it's the picture that counts ;) Your ice is looking very nice, procedural bump mapping? good luck, -Mark ------------------------------- My current question: "theme refraction": Optical thickness for a) glass is 0.33, for b) water 0.25 and c) ice 0.236? It's right? A new picture I have added here... rendering times over 24:35 minutes... uargh :-D best wishes, good renderings, Frank
