Alain schrieb:
> Controls the pretrace passes. can be used to reduce some artefacts. The 
> value is a ratio of the horizontal dimention of the image been rendered.
> There is no point to set pretrace_end to anything lower than 
> 2/image_width meaning a last pretrace step of 2x2 pixels tiles.

Well, there is: It further reduces the need for final-trace gathering of 
radiosity samples (which invariably lead to artifacts).

> Interior scenes ferquently need a value of 2 to 4. If the radiosity 
> evvect need to take into acount something behind a pane of glass, and 
> you do a single pass rendering, you need at least a value of 3, 2 levels 
> been used to get through the pane.

This is not so: The radiosity recursion level is /only/ increased by 
genuine "radiosity bounces".

Conversely, however, radiosity bounces /do/ affect the /general/ trace 
level, so a max_trace_level barely enough to reach through a pane of 
glass will not be enough for radiosity to "see" through it. (POV-Ray 3.6 
and earlier also added other troublesome issues in this context, leading 
to the infamous black-splotch artifacts.)

(Your statement was actually true for some older POV-Ray 3.7 betas, but 
this has been changed again.)

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