Darren New wrote:
> Severi Salminen wrote:
>> Glass has about 4% reflection coefficient when angle of incidence is 0.
>> I guess this 4% holds true both when entering glass and exiting it?
> 
> It's more complicated than that in reality. Light doesn't reflect from
> the surface of the glass. It reflects inside the glass. It only seems
> like it reflects from the surface because different paths that reflect
> at different depths in the glass cancel out. 

Thanks for the clarification. The important part is the actual net
effect that affects the image. If the 4% (or whatever n1 and n2 gives)
holds true in most cases and is accurate within some margin - that is
suitable for now.

> I mean, if you're talking about "physically-accurate" tracing. :-)

Definitely :=)

But at this point I'm mostly interested in reproducing the effects that
make bigger difference in final image. For example:

having no shadows is worse than having inaccurate sharp shadows
inaccurate sharp shadows < inaccurate area_light approximation

Lack of accurate GI < lack of dispersion

lack of dispersion < slightly inaccurate refraction model (light bends a
bit too far etc.)

etc.

So things must be fixed in priority order. Here is the same scene with
5% reflection in the spheres - including the light that tries to exit
the sphere :) 46000 passes. Quite smooth rendering.

I'm now experimenting with Halton sequence that replaces totally random
rays. It is deterministic but should give more uniform distribution. So
less samples are needed for certain noise level. Not working properly yet...

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