> "And" <49341109@ntnu.edu.tw> wrote:

>> Maybe I can express my opinion.
>> Once I rendered a scene with large area surfaces that switched the
>> specular/phong on. The multiple light sources can make it slow truely.
>> I only have the experience that time. Because I almost use the reflection
>> instead of specular.
>
> This only gives good results of you use photons, and I've never had good results
> with photons.
>
> Regards,
> A.D.B.
>
>
>

With photons, you need to set the first active object lighted with a 
target directive.
You follow that with reflection on and/or refraction on.
If you have several stacked active objects, only the first in line 
should be set as a target. If you set an object as a target and that 
object is beheind another, all photons shoot in it's direction will be 
intersepted by the first object. If you use count, it will steal photons 
from the other objects...

If you have one problem object, you can use target float. That value 
will multiplied with the spacing. Usefull for an object needing a high 
density of photons while most others only need a moderate coverage.

I find it beter to use spacing rather than count. That's even more 
importent when you have several light_source and target objects.
You need to adjust spacing according to the dimention of your objects 
relative to the scale of the scene. If, on average, 1 unit covers only a 
few pixels, use a large spacing, but if 1 unit could visualy cover a 
large area, use a small spacing.

Normaly, I don't set any other parameter other than spacing and autostop 
0 and, maybe, jitter.

Remember that the camera NEVER directly see the photons. Photons can 
cause caustics, but never ever cause highlights.

If you use reflection to get your highlights, the light_source must be 
visible by using looks_like or been unioned with some object.


Alain

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