No refelctions of dispersion on ground

[umix72]

Hello,

i have attached two image files to demonstrate what my issue is. i am experimenting with dispersions and refrections of light in different glass objects.
to get the refractions and dispersions are not the problem, the problem is, that these rainbow-effect do not reflect on the ground.
i tried to make the ground diffuse or shiny oder glossy, but the dispersions do not reflect on the ground.
but that is exactly that, what i wan't to have

i hope, someone can help me to understand, why the rainbow-effect don't reflect on the ground.

* The two example images were created in Rhino with the Octane-Plug-In.

Kind Regards,

umix

[bepeg4d]

Hi umix,
you need a very strong and small light source, PMC kernel, for good caustics and dispersion.
Here is an example with c4doctane:

ciao beppe

[nuno1980]

Too high dispersion -> the real life does NOT EXIST it...

But what's the specular material of prism? Glass?

If you want:
- glass prism - ior 1.509 and dispersion coefficient 0.006
or
- diamond prism - ior 2.379 and disp 0.011

[umix72]

Hi beppe and nuno,

many thanks for your answers. I think my problem is the lighting. beppe, can you please tell me with which lighting you created your very nice example? I think that's where my problem lies. Could you briefly describe to me which light you used and which settings you used?

In my example i used a rectangle polygon with a assigned diffuse material and blackbody-emission as scene-light. It seems, this is not the right way?

Thanks a lot and greetings,

ciao,
umix

[bepeg4d]

Hi umix72,
the dimensions of the light have a great impact on the caustic/dispersion pattern, in my example the light was 100cm in height, but only 1cm wide.
As you can see in your example, the shadows are very blurry, so the emitter is too big for a good caustic/dispersion pattern.
ciao beppe

[umix72]

Oh, could that possibly have something to do with the units? In Rhino, the unit is given in millimeters, that is what i work with. Do i have to scale my scene up to the meter so that it works correctly or is the unit important only if i export the entire scene to Octane-Standalone? Octane will only work (physically) correctly if Rhino is specified as a unit of meters?

ciao,
umix

[bepeg4d]

Hi umix,
sorry not a Rhino user, anyway, try to scale only the emissive geometry, you need to have hard shadows too.
You can also use the Daylight system with sun to obtain the effect.
What are the dimensions in mm at the moment?
ciao beppe

[umix72]

Hi beppe,

the polygon that actually works as a lightsource is a rectangle polygon with the dimensions 5×5 mm and a blackbody emission with 6500k and a power of 500 watt. But i think, this shape is far to small to work correctly? First i will try to scale up the whole scene from millimeters to meters and then see if it brings somehting.

Thanks for your help.

Ciao,
umix