Blender Internal Dispersion and Caustics – Explained


https://i.ytimg.com/vi/gIT1g_LMd3E/hqdefault.jpg



…using the official 2.58 release

source


30 responses to “Blender Internal Dispersion and Caustics – Explained”

  1. @NionsChannel
    …continued
    I'll try a comparison of max vs avg, both with 6 samples, for comparison.

    The only reason why I think that the purple sample is important as well, is because it does have the highest IoR while red has the lowest one, relative to usual materials…
    So the difference in the two red channels will be the biggest and thus hardly neglectable. More than six samples shouldn't be too necessary though.

  2. @NionsChannel
    I also thought about it some more…
    It would be overkill of freedom (not too much slower in case of calculation, though), but you'd actually need to multiply each channel seperately by some factor that determins the sensitivity to a certain frequency range for the given colour-channel. While the red channel does react to purple light, it doesn't do so as much as it does for red light.
    Maybe, changing the colour of the sample is enough for that, though…
    continued…

  3. @Kram1032 I just thought about it once more: given enough samples, your approach is probably closer to realism. The thing is: lets say you get the value 1 for a color sample. If you make an average calculation, you only see the full occurence of that color, if the other samples for the color channel(s) also have the value 1. On the other hand: if you take the maximum and the samples are close to each other, you only see mixed colors and loose elementary colors.

  4. @NionsChannel
    thanks for the help πŸ™‚ That worked.
    I did a slightly different version of yours, though:
    First, I used six samples, adding one in the purple range, which you missed. Second, I assumed it to be more realistic if you add the different values together, rather than choosing the bigger one, so I did some adding and then renormalization (three samples per colour -> multiply by constant .333 grey) instead.

  5. @NionsChannel Ah, thanks, that's probably it πŸ™‚
    I looked at that and it's deactivated by default. I'll immediatedely try it with set to Transparency Checked, Option=Raytraced πŸ™‚

  6. You are the hackiest Blender hacker I've seen before, Nion! πŸ™‚
    You ought to make a proposal to implement this tricky dispersion effect to BI as the material's feature. I'm not sure the same possible about caustics (which is really great btw and can be a real exit for every PC without a powerful GPU). Just the matter of render times and setups.

  7. Hmmm, this looks awesome.
    But when I try replicating this effect, my Nodes don't use the transparency at all :-/
    Any ideas what could go wrong?

    (The transparency setting is greyed out. I set all my samples to RayTraced transparency. The samples each would render fine, but when combining via nodes, no transparency is used. Specular dispersion on solids looks nice too, but :-/)

  8. A fantastic tutorial that my highschool physics teacher would have approved of. Thanks for posting something so insightful, Nion. Exactly the sort of thing we need more of.
    You're ridiculously talented. I've shown friends a lot of your effects reels and clips, and everyone has been like "DAYUM! You should get HIM to help make your movie!" (My ex used to go to extremes to get me away from the computer and into her pants, and wasn't keen on explanations about the workload of other animators…)

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