chromatic spectrum in a diamond

[roppin]

I have tried to make the spectrum effect in three renders rgb and composit them together later this is all fine except I don't get a linear spectrum but rather spotted is there a way to fake this in a better way?

[Da_elf]

can you post the seperate layers and final mix to show what you mean by spotted?

[roppin]

here it is:

[Da_elf]

can we see the splits too? i had an idea on how to get the diamond done, can you tell me how to make a diamon? i know its not just a faced sphere.
im thinking maybe if you had mask for the diamond. (black and white) then also had 3 passes on the diamond each using a sliiiiightly different IOR. then in photoshop for each layer you delete two color channels so that you have a red diamond, a blue one then a red one. then use additive blending you would be able to combine the colors to regrain your white and only the areas that differ would show the coloring thus giving you your color spectrum in those areas. then mask the diamond so you can place it on your background...beats me if it would work but it sounds plausable.

[Gijs]

well, what else did you expect? If you have real diffraction, it depends on the amount of samples if you get a transition or spots like you have here. Basically what you have done is rendering 'three samples' (without randomization) hence the three spots.

edit: I mean dispersion, not diffraction

[roppin]

I did expect this result, but how can I get a better? no dots but the whole spectrum

[Gijs]

the only way I can think of is using more samples, thus more different color renderings. I think the best is to render all different layers in only one color light, for example all in red, and only change the IOR between renderings, then re-color each resulting 'channel' in photoshop by adjusting the hue for every rendering. The more you come near to endless amount of channels, the more it will come near to reality.

[DanielBrew]

You could animate the light colour and the IOR of the diamond, say over 25 frames. Then save the refract and caustics g-buffer output channels and composite onto a render with caustics turned off. I haven't tried this BTW.

Dan

[Da_elf]

i might have over done it with the ior shifts between colors.

[jujubee]

Nice one Elf.

[Gijs]

Indeed, pretty clever.

[Da_elf]

all i did was use IOR 2.47 and had the diamond set to diffuse color black refraction color 255 blue, then rendered that. altered the IOR to 2.57 then rendered with refraction color Green then changed IOR again to 2.67 and made it Red. these colors i mixed in AE with the blue on bottom set to blending mode normal, then red and green ontop both set to blending mode lighten, i found blending mode add was way too bright.

[jacksc02]

where are the caustics da elf!!

[Da_elf]

so sue me, i was lazy hehehe

[roppin]

all i did was use IOR 2.47 and had the diamond set to diffuse color black refraction color 255 blue, then rendered that. altered the IOR to 2.57 then rendered with refraction color Green then changed IOR again to 2.67 and made it Red. these colors i mixed in AE with the blue on bottom set to blending mode normal, then red and green ontop both set to blending mode lighten, i found blending mode add was way too bright.

exactly as I did it. I think the stone is OK but The problems start with the caustics