Am 16.03.2017 um 16:06 schrieb muyu:

> I am using the following code:
> 
> #version 3.7;
> 
> global_settings {
>    assumed_gamma 1.0
>    ambient_light 0.0
>    max_trace_level 100
>    adc_bailout 0.0
> 
>    radiosity {
>       count 1500
>       gray_threshold 0.00
>       error_bound 0.05
>       brightness 1.0
>       normal on
>       recursion_limit 20
>    }
> }
...

> The recursion_limit has been set as the maximum. But it still a little bit
> underestimate.

Whether this is to be expected depends on how much energy the canopy
absorbs per "bounce".

For instance, if 70% of the light is either reflected or transmitted per
bounce, the error due to reaching the maximum recursion limit should be
less than 0.1% of the total incoming energy; but if 80% is reflected or
transmitted, that error already exceeds 1%, and at 90%
reflection/transmission it reaches 12%.

> 1) Do you have other suggestions to increase the accuracy?

No, not really. The other radiosity settings should just affect
low-frequency noise-ish artifacts intrinsic to the sampling and caching
mechanisms.


> 2) gray_threshold has to be set as 0.0? I found that this impacts significantly
> the result.

Yes, a setting of 0 (being the default, and serving as a special value
indicating that the feature is to be turned off) is the most realistic
(to the extent that POV-Ray's internal naive RGB colour math is
realistic, compared with a full-fledged spectral colour model; but you
seem to be using POV-Ray in a kind of monochromatic mode anyway, so the
naive math should be fine for you).


> 3) brightness seems has no significant on the result. Is it correct to set
> brightness as 1.0?

If you change brightness significantly, you /should/ see a difference.
But 1.0 (also the default) is the most realistic setting.

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