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I'm getting some strange results with the Heightfield/Pattern combination
when used with the phase modifier and would like some comments please. I've
included the code in povray.binaries.scene-files under the subject
heading "Heightfield / Pattern bug".
Basically using phase 0 is OK, but anything else starts to look really bad.
Am I doing something wrong or is this a bug?
MegaPov 0.5
Windows
P2-233
96M RAM
Thanks,
Lee
p.s. Please reply to the group as I've not been able to dial into my ISP for
the last day and a half.
--
lee### [at] prodigy net
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From: Bob Hughes
Subject: Re: Pattern and Heightfield, Win MegaPov 0.5
Date: 13 Jun 2000 15:54:22
Message: <3946916e@news.povray.org>
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"Lee Brown" <lee### [at] prodigynet> wrote in message
news:39457f7c$1@news.povray.org...
| I'm getting some strange results with the Heightfield/Pattern combination
| when used with the phase modifier and would like some comments please. I've
| included the code in povray.binaries.scene-files under the subject
| heading "Heightfield / Pattern bug".
|
| Basically using phase 0 is OK, but anything else starts to look really bad.
|
| Am I doing something wrong or is this a bug?
|
| MegaPov 0.5
| Windows
| P2-233
| 96M RAM
I'd have to see the pov script to say anything definite, and even then I'm no
expert.
What occurs to me is that maybe there is turbulence used in that and phase can
really change a pattern that isn't regular to begin with. Could be anything
though.
Bob
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From: Lee Brown
Subject: Re: Pattern and Heightfield, Win MegaPov 0.5
Date: 13 Jun 2000 22:24:21
Message: <3946ecd5@news.povray.org>
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"Bob Hughes" <per### [at] aolcom?subject=PoV-News:> wrote in message
news:3946916e@news.povray.org...
> "Lee Brown" <lee### [at] prodigynet> wrote in message
> news:39457f7c$1@news.povray.org...
> | I'm getting some strange results with the Heightfield/Pattern
combination
> | when used with the phase modifier and would like some comments please.
I've
> | included the code in povray.binaries.scene-files under the subject
> | heading "Heightfield / Pattern bug".
> I'd have to see the pov script to say anything definite, and even then I'm
no
> expert.
The code is located in povray.binaries.scene-files under the subject heading
"Heightfield / Pattern bug"
> What occurs to me is that maybe there is turbulence used in that and phase
can
> really change a pattern that isn't regular to begin with. Could be
anything
> though.
Well the heightfield which is scaled to be about .3 pov-units high starts
slamming up and down hard and going past the 0.3 unit scaling. Very weird.
I'd really appreciate it if somebody took a look.
Thanks,
Lee
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From: Bob Hughes
Subject: Re: Pattern and Heightfield, Win MegaPov 0.5
Date: 14 Jun 2000 00:25:41
Message: <39470945@news.povray.org>
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| Well the heightfield which is scaled to be about .3 pov-units high starts
| slamming up and down hard and going past the 0.3 unit scaling. Very weird.
You're right. And it's wrong. Or at least I'm fairly sure it is. Correct
behaviour for it would be to shift the pattern from highs to lows and lows to
highs, a kind of traded places thing. I gave 'ripples' a try and moved the
camera up in the y axis some to get a good typical view. A ripple pattern
should definitely only roll along like waves on the surface of a pond from a
pebble dropped into it. The same unusual distortion takes place though,
ultimately collapsing the crests instead of just propagating them.
I envision a bug report for the povray.unofficial.patches group.
Bob
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From: Bob Hughes
Subject: Re: Pattern and Heightfield, Win MegaPov 0.5
Date: 14 Jun 2000 00:42:24
Message: <39470d30@news.povray.org>
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I was looking at the ripples pattern some more, scaled to a regular 1 unit
size (also in the y axis). Appears what is happening might be that the phase
suddenly reverses the 0 to 1 bounds into a -1 to 1 zone instead. Why it
would only start to (and end) at a range of phase 0.16 to 0.84 (that's a guess
by the way) and not for all parts of phase 0 to 1 is beyond my understanding.
Perhaps related to sine and/or cosine?
Bob
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From: Lee Brown
Subject: Re: Pattern and Heightfield, Win MegaPov 0.5
Date: 14 Jun 2000 04:28:22
Message: <39474226@news.povray.org>
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> You're right. And it's wrong. Or at least I'm fairly sure it is.
Correct
> behaviour for it would be to shift the pattern from highs to lows and lows
to
> highs, a kind of traded places thing. I gave 'ripples' a try and moved
the
> camera up in the y axis some to get a good typical view. A ripple pattern
> should definitely only roll along like waves on the surface of a pond from
a
> pebble dropped into it. The same unusual distortion takes place though,
> ultimately collapsing the crests instead of just propagating them.
OK, so I'm not going crazy :) Well at least not where MegaPOV is concerned
anyway.
Bumps does something similar.
> I envision a bug report for the povray.unofficial.patches group.
I'll put one together (once I've read the FAQ) tonight and post it in that
group.
Regards,
Lee
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