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Hello again!
Now my light is REALLY strange...
I have a sort of yellow thing that is stuck to the wall, butthe shadow is as
if my thing was far from the wall...
Plus, there is a brass ball that have a really strange shadow O_o
And if I apply a scale 20, the artifacts diseapear 0_o
Here is the image :
http://dragons.masters.free.fr/images/demo3.png
Here comes the code :
#include "colors.inc"
#include "textures.inc"
#include "metals.inc"
global_settings {
max_trace_level 20
}
// Change this and you will see
// that the artifacts chenge... :-S
#declare echelle = 1;
camera {
location <-0.00,-0.7957,-1.308>*echelle
look_at <-0.0,-.791,-1.30001>*echelle
}
#declare my_object = union {
union {
light_source {
<-0.22,-0.75,-1.40>
White
}
union {
box {
<0.025,-0,-1.3>
<-0.025,-0.87,-1>
}
mesh {
triangle {
<0,-0.79,-1.29999>
<0.004,-0.795,-1.29999>
<0,-0.7925,-1.303>
}
triangle {
<0,-0.79,-1.29999>
<-0.004,-0.795,-1.29999>
<0,-0.7925,-1.303>
}
triangle {
<0,-0.795,-1.29999>
<0.004,-0.795,-1.29999>
<0,-0.7925,-1.303>
}
triangle {
<0,-0.795,-1.29999>
<-0.004,-0.795,-1.29999>
<0,-0.7925,-1.303>
}
triangle {
<0,-0.795,-1.29999>
<-0.004,-0.795,-1.29999>
<0,-0.79,-1.2999>
}
triangle {
<0,-0.795,-1.29999>
<0.004,-0.795,-1.29999>
<0,-0.79,-1.29999>
}
inside_vector <0,1,0>
texture {
pigment { Yellow }
}
}
sphere {
<0,-0.7935,-1.301>
0.001
texture {
Brass_Metal
}
}
texture {
pigment { Red }
}
}
}
}
object {
my_object
scale echelle
}
Post a reply to this message
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Gyscos nous apporta ses lumieres en ce 12/04/2006 04:38:
> Hello again!
> Now my light is REALLY strange...
>
> I have a sort of yellow thing that is stuck to the wall, butthe shadow is as
> if my thing was far from the wall...
> Plus, there is a brass ball that have a really strange shadow O_o
>
> And if I apply a scale 20, the artifacts diseapear 0_o
>
> Here is the image :
>
> http://dragons.masters.free.fr/images/demo3.png
>
> Here comes the code :
>
>
>
> #include "colors.inc"
> #include "textures.inc"
> #include "metals.inc"
>
> global_settings {
> max_trace_level 20
> }
>
>
> // Change this and you will see
> // that the artifacts chenge... :-S
>
> #declare echelle = 1;
>
> camera {
> location <-0.00,-0.7957,-1.308>*echelle
> look_at <-0.0,-.791,-1.30001>*echelle
>
> }
>
>
> #declare my_object = union {
> union {
> light_source {
> <-0.22,-0.75,-1.40>
> White
> }
> union {
> box {
> <0.025,-0,-1.3>
> <-0.025,-0.87,-1>
> }
> mesh {
> triangle {
> <0,-0.79,-1.29999>
> <0.004,-0.795,-1.29999>
> <0,-0.7925,-1.303>
> }
> triangle {
> <0,-0.79,-1.29999>
> <-0.004,-0.795,-1.29999>
> <0,-0.7925,-1.303>
> }
> triangle {
> <0,-0.795,-1.29999>
> <0.004,-0.795,-1.29999>
> <0,-0.7925,-1.303>
> }
> triangle {
> <0,-0.795,-1.29999>
> <-0.004,-0.795,-1.29999>
> <0,-0.7925,-1.303>
> }
> triangle {
> <0,-0.795,-1.29999>
> <-0.004,-0.795,-1.29999>
> <0,-0.79,-1.2999>
> }
> triangle {
> <0,-0.795,-1.29999>
> <0.004,-0.795,-1.29999>
> <0,-0.79,-1.29999>
> }
> inside_vector <0,1,0>
>
> texture {
> pigment { Yellow }
> }
> }
> sphere {
> <0,-0.7935,-1.301>
> 0.001
> texture {
> Brass_Metal
> }
> }
> texture {
> pigment { Red }
> }
> }
> }
> }
>
>
>
> object {
> my_object
> scale echelle
> }
>
>
>
You aparently tend to use a small scale, or very large units. The disapearance of the
problem by
scaling up the scene point to rounding errors introduced by the arithmetic processor
(FPU).
A possible solution would be to use another, smaler "base unit".
--
Alain
-------------------------------------------------
'First things first -- but not necessarily in that order' -- Dr Who
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A smaller base units ?...
What do you mean ?
Instead of using 0.1, use 1 ? or 0.01 ?...
Post a reply to this message
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"Gyscos" <gys### [at] gmail com> wrote in message
news:web.443e065fff7865861ba56a630@news.povray.org...
>A smaller base units ?...
> What do you mean ?
> Instead of using 0.1, use 1 ? or 0.01 ?...
>
If this is part of your aircraft, then you seem to be using 0.035 povray
units to represent about 1 metre.
If you use 1 metre = 1 povray unit, then you'll get far less of the sorts of
problem you are getting.
Regards,
Chris B.
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Chris B <c_b### [at] btconnectcomnospam> wrote:
> If this is part of your aircraft, then you seem to be using 0.035 povray
> units to represent about 1 metre.
> If you use 1 metre = 1 povray unit, then you'll get far less of the sorts of
> problem you are getting.
I don't think that's a problem, unless he is using measures of the order
of magnitude of one nanometer.
Double-precision floating point numbers are quite flexible, and using
0.035 as unit is about exactly as accurate as using 1 as unit. It's only
when you start going to real extremes (like using 0.000000035 as unit)
when you might start getting problems.
--
- Warp
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"Warp" <war### [at] tagpovrayorg> wrote in message
news:443e1278@news.povray.org...
> Chris B <c_b### [at] btconnectcomnospam> wrote:
>> If this is part of your aircraft, then you seem to be using 0.035 povray
>> units to represent about 1 metre.
>> If you use 1 metre = 1 povray unit, then you'll get far less of the sorts
>> of
>> problem you are getting.
>
> I don't think that's a problem, unless he is using measures of the order
> of magnitude of one nanometer.
>
> Double-precision floating point numbers are quite flexible, and using
> 0.035 as unit is about exactly as accurate as using 1 as unit. It's only
> when you start going to real extremes (like using 0.000000035 as unit)
> when you might start getting problems.
>
> --
> - Warp
Hi Warp,
I was just going on the two problems that Gyscos has reported.
Alain indicated that scaling up by a factor of about 20 gets rid of the
artifacts reported in this thread and I find that scaling up by about the
same factor makes the two sets of artifacts from the thread 'Light passing
through my wall' get smaller and then dissapear, because the camera ends up
20 times further away and the artefacts seem to be of a fixed size.
I'm not sure the problem I looked at is necessarily to do with the accuracy
of the floating point calculations (though it seems worth considering). In
the simplified example I posted in the other thread, all of the objects were
of a fair size. The camera is close-in to emphasize the artifacts, but not
close enough to get to the sort of extremes you mention. In my example in
that thread, commenting out the second box makes the artifacts dissapear,
which is odd as it's nowhere near the offending objects and is well out of
camera shot. I looked at this on POV-Ray 3.6 and interestingly Alain has
indicated that with a 3.7 beta the artifacts are always present.
So I'm not sure what the cause of either of these problems is, and I can see
that it would take a fair time to change the units throughout his SDL, but
that does seem to me to be a workaround for both problems and one that
Gyscos may wish to consider. In addition, from a personal perspective, I
found it quite difficult to look at the problem having to think about
everything to 4 decimal places, but of course that's just down to what
you're used to.
Regards,
Chris B.
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Ok, i guess you're right... I'll just scale it 20 times...
But doesn't seem to be a real solution, is it ?...
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