On 18-6-2013 10:52, scott wrote:
>> There is a much better solution.
> ...
>> The scene does not need the *emission* of the *visible* sphere as a
>> light source.
>
> As I said before, there isn't any need to try this for radiosity, it
> will just cause problems like you experienced. It's only in the code as
> it is needed for mcpov (where is works fine).

But mcpov has other problems of its own, as Clipka explained some time ago.

>
>> It only needs the light source itself. So, the solution is
>> to put the sunlight at the standard SunPos position, and the *visible*
>> sphere and its radius at sp/1000.
>
> I don't know if there are any accuracy issues related to having a
> light_source a very large distance away, I expect it may cause some
> shadow artifacts? The length of the vector from SunPos is quite
> arbitrary, so in every scene you just need to find the max distance it
> works at, then I'd probably divide by 10 or 100 just to be sure you're
> not near the accuracy limit.

I have never met any problems or artefacts when using SunPos so, imho, 
there is no need to divide.

>
>> In addition, just make emission of the
>> sphere equal to 1.
>
> The problem with that is the sun will look unrealistically dim compared
> to the sky when visible in any reflections, especially darker low-level
> reflections (eg a black car). You could set emission to 0 and ambient to
> the original physically correct 1.6e9 * EXP, but I think that would
> still influence the radiosity algorithm and give you back the bright
> splotches again.

Maybe, but those are special cases needing special solutions.

>
> At this point I usually fire up mcpov :-)

<grin>

Thomas

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