Tom Melly wrote:
> 
> Hi,
> 
> I recently rendered an old scene of mine in mp6 and noticed that a hf
> suddenly acquired lots of holes (well, I assume that they're holes). I
> re-rendered the scene in plain 'ol pov and it's fine.
> 
> Is this a known problem or should I post more detail (or both)?

Is this hf smooth? In this case try to add double_illuminate to height
field, this should fix this problem. I'm not sure, what causes this, but
I guess, that it is due to normal average between vertexes of smooth
height field: normal gets oriented in "opposite direction" to up and
therefore surface is not lighted. 
There was discussion about this, see "Heightfield smooth problem" in
this group, started 2000-06-13.

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