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A long time ago, when I first started playing with POVRay, it was quite the
trend to have a short POV script for a signature. No one does that anymore it
seems, but I always wanted to try it, so I did! Except the lathe object in the
script appears with artifacts...
I've tried antialiasing, raising the max_trace_level, and adding the sturm
keyword, but none worked. I am using version 3.6.1c.
camera{location y*10 look_at 0}
light_source{<1,30,1>rgb 1}
difference{
lathe{
bezier_spline
4,
<0,-2>,<2.5,-1.95>,<1,2>,<0,3>
rotate x*90
texture{
pigment{
bozo scale .25
color_map{
[.2 rgb 1.5]
[1.0 rgbt<1.6,1.5,1.5,.3>]
}
}
finish{
specular 1
roughness .0005
reflection .85
irid{.25 thickness .25 turbulence 0.5}
}
}
}
prism{
linear_sweep
linear_spline
0,6,28,
<-.05,-.33>,<-.38,.66>,<-.71,-.33>,<-.61,-.33>,<-.51,0>,
<-.25,0>,<-.15,-.33>,<-.05,-.33>,<-.46,.1>,<-.38,.46>,
<-.31,.1>,<-.46,.1>,<.05,-.33>,<.05,.66>,<.46,.66>,
<.66,.46>,<.66,.26>,<.46,.06>,<.15,.06>,<.15,-.33>,
<.05,-.33>,<.15,.56>,<.41,.56>,<.56,.41>,<.56,.31>,
<0.41,.16>,<.15,.16>,<.15,.56>
texture{
pigment{rgb<.6,.4,.1>}
finish{ambient .15 brilliance 5 metallic specular .8 roughness .01
reflection .65}
}
}
}
(Sorry about the lousy formatting...signatures were crammed to make them as
short as possible. I tried to break it up so it is mostly readable :-) )
Thanks in advance!
~Angela Perry
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On Thu, 17 Jul 2008 00:30:22 EDT, "Angela" <ang### [at] yahoo com> wrote:
>
>I've tried antialiasing, raising the max_trace_level, and adding the sturm
>keyword, but none worked. I am using version 3.6.1c.
Have you tried the sturm keyword? I've found that if I don't use it I get
artefacts when the object intersects the horizon.
--
Regards
Stephen
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Stephen napsal(a):
> On Thu, 17 Jul 2008 00:30:22 EDT, "Angela" <ang### [at] yahoo com> wrote:
>
>> I've tried antialiasing, raising the max_trace_level, and adding the sturm
>> keyword, but none worked. I am using version 3.6.1c.
>
> Have you tried the sturm keyword? I've found that if I don't use it I get
> artefacts when the object intersects the horizon.
reread the post you quote. You can see she did have tried.
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On Thu, 17 Jul 2008 15:26:05 +0200, Jan Dvorak <jan### [at] centrum cz> wrote:
>Stephen napsal(a):
>> On Thu, 17 Jul 2008 00:30:22 EDT, "Angela" <ang### [at] yahoo com> wrote:
>>
>>> I've tried antialiasing, raising the max_trace_level, and adding the sturm
>>> keyword, but none worked. I am using version 3.6.1c.
>>
>> Have you tried the sturm keyword? I've found that if I don't use it I get
>> artefacts when the object intersects the horizon.
>
>reread the post you quote. You can see she did have tried.
I shouldn't do these thinks quickly at work :(
--
Regards
Stephen
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That gives me an idea though! Maybe I'll try translating it away from the
origin, just to see if it is the horizon :-) For the location of the artifacts,
that makes sense.
I'm at work too (darn it) so I'll try it when I get home.
~Angela Perry
Stephen <mcavoysAT@aolDOTcom> wrote:
> On Thu, 17 Jul 2008 15:26:05 +0200, Jan Dvorak <jan### [at] centrum cz> wrote:
>
> >Stephen napsal(a):
> >> On Thu, 17 Jul 2008 00:30:22 EDT, "Angela" <ang### [at] yahoo com> wrote:
> >>
> >>> I've tried antialiasing, raising the max_trace_level, and adding the sturm
> >>> keyword, but none worked. I am using version 3.6.1c.
> >>
> >> Have you tried the sturm keyword? I've found that if I don't use it I get
> >> artefacts when the object intersects the horizon.
> >
> >reread the post you quote. You can see she did have tried.
>
> I shouldn't do these thinks quickly at work :(
> --
>
> Regards
> Stephen
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"Angela" <ang### [at] yahoo com> wrote:
> A long time ago, when I first started playing with POVRay, it was quite the
> trend to have a short POV script for a signature. No one does that anymore it
> seems, but I always wanted to try it, so I did! Except the lathe object in the
> script appears with artifacts...
>
Offhand, it looks like the artifacts are from self-shadowing. After trying the
usual tricks (translating or rotating by a very small amount, etc), I tried
using no_shadow, and the upper ones disappeared. Unfortunately, this visibly
changes the image without removing some of the lower artifacts. I am starting
to suspect a bug.
In any case, another work around that reduces (but does not entirely remove) the
artifacts is multiplying the light_source location vector by a higher number.
Code:
light_source{<1,30,1>*100 rgb 1}
With all else the same, the upper, darker artifacts do go away.
HTH,
-Reactor
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"Angela" <ang### [at] yahoo com> wrote in message
news:web.487f65ae64250a2e64eed08a0@news.povray.org...
> That gives me an idea though! Maybe I'll try translating it away from the
> origin, just to see if it is the horizon :-) For the location of the
> artifacts,
> that makes sense.
I've had similar problems in the past when the change of direction between
two points is too big. Although it may be possible to find a position where
the artifacts are not very apparent, that's a bit fiddly.
I think you'll find it's a more robust solution to simply add a midpoint,
reducing the change of direction between each set of points. For example:
camera{location -z*10 look_at 0}
light_source{<1,1,-30> rgb 1}
lathe{
bezier_spline
8,
<0,-2>,<1.5,-1.985>,<1.49,-0.5>,<1.24,0.5>
<1.24,0.5>,<0.99,1.5>,<0.5,2.5>,<0,3>
pigment{rgb <1,1,1>}
}
Warning: I've flipped the axes in this example to the default ones which I'm
more accustomed to and which avoid having to rotate the lathe object.
Regards,
Chris B.
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"Chris B" <nom### [at] nomail com> wrote:
> I think you'll find it's a more robust solution to simply add a midpoint,
> reducing the change of direction between each set of points.
That fixed it Chris, thank you! And thanks everyone else for all the help and
suggestions :-)
~Angela Perry
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I ran your eample also version 3.6.1c and don't get any Artifacts.
I used antialise:
+A0.1 +AM2 -J.25 +R3
and tested at two sizes 400*400 and 800*800
No problems anywhere!
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On Thu, 17 Jul 2008 22:00:14 EDT, "Angela" <ang### [at] yahoo com> wrote:
>"Chris B" <nom### [at] nomail com> wrote:
>> I think you'll find it's a more robust solution to simply add a midpoint,
>> reducing the change of direction between each set of points.
>
>That fixed it Chris, thank you! And thanks everyone else for all the help and
>suggestions :-)
>
I'm pleased that you got a solution. I found that when I rotated the lath by 5
degrees the artefacts were not visible.
--
Regards
Stephen
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