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I have this small problem... I have a very large object
that is very far from the center ( <0,0,0>), but it seems
that pov prunes objects that are not inside <+-1000000,
+-1000000,+-1000000>... Is there a way of settings this?
Best,
S.
--
----------------------------------------------------------
Steven Pigeon Ph. D. Student.
University of Montreal.
pig### [at] iro umontrealca Topics: data compression,
pig### [at] jspumontrealca signal processing,
ste### [at] researchattcom non stationnary signals
and wavelets.
----------------------------------------------------------
http://www.iro.umontreal.ca/~pigeon
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Steven Pigeon wrote:
> I have this small problem... I have a very large object
> that is very far from the center ( <0,0,0>), but it seems
> that pov prunes objects that are not inside <+-1000000,
> +-1000000,+-1000000>... Is there a way of settings this?
>
> Best,
>
> S.
Oh, yeah, I use version 3.1a for windows.
It seems in fact that the bug is much more perverse...
#declare EarthMoonDistance = 469928448; // Earth-Moon distance
#declare EarthRadius = 6379439.6; // in meters (thus, 1 pov unit =~=
1 m)
#declare MoonRadius = 3476183; // for now
box
{
0, MoonRadius
translate <0,-EarthRadius,0> + EarthMoonDistance*vnormalize(<0,0.5,1>)
pigment { Green }
}
Yields a visible box, but:
sphere
{
0, MoonRadius
translate <0,-EarthRadius,0> + EarthMoonDistance*vnormalize(<0,0.5,1>)
pigment { Green }
}
does not yield a visible sphere... the object doesn't even exist!
suggestions?
Best,
S.
----------------------------------------------------------
Steven Pigeon Ph. D. Student.
University of Montreal.
pig### [at] iroumontrealca Topics: data compression,
pig### [at] jspumontrealca signal processing,
ste### [at] researchattcom non stationnary signals
and wavelets.
----------------------------------------------------------
http://www.iro.umontreal.ca/~pigeon
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> suggestions?
>
1. Fix the source.
or....
2. Scale your distances to fit within POV's current bounds. If your moon is 100x
closer and
100x smaller, the error in parellax will be well under one pixel.
Dan
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Due to prescion limitations of Float math, Povray is compiled
by default with the following:
Anything below 0.001 is considered 0.0
Anythung beyond +/- 1e7 is non exsistant
Don't try to be 100% accurate. Povray isn;t a physics real
world modeler. its an Artistic Program. As long as it looks
right to you then its accurate =}
"fixing" the source will give prescion errors.
Dan Connelly wrote:
>
> > suggestions?
> >
>
> 1. Fix the source.
>
> or....
>
> 2. Scale your distances to fit within POV's current bounds. If your moon is 100x
closer and
> 100x smaller, the error in parellax will be well under one pixel.
>
> Dan
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Matthew Corey Brown - XenoArch wrote:
>
> Due to prescion limitations of Float math, Povray is compiled
> by default with the following:
>
> Anything below 0.001 is considered 0.0
> Anythung beyond +/- 1e7 is non exsistant
>
> Don't try to be 100% accurate. Povray isn;t a physics real
> world modeler. its an Artistic Program. As long as it looks
> right to you then its accurate =}
>
> "fixing" the source will give prescion errors.
>
POV sets its limits rather conservatively, and in some cases
does calculations in a fashion which make it more susceptible
to precision limits than it needs be.... doing things like taking
squares and squareroots in nonoptimal sequence.
I agree, though -- there often isn't a need to use such large numbers,
as I pointed out.
Dan
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Matthew Corey Brown - XenoArch wrote:
> Due to prescion limitations of Float math, Povray is compiled
> by default with the following:
>
> Anything below 0.001 is considered 0.0
> Anythung beyond +/- 1e7 is non exsistant
Well, pov uses DOUBLEs, and not FLOATs, and the epsilonis 1e-6...
not 1e-3. I've checked the source.
Besides, I could show you a couple of pictures where a difference
of 0.001 is visible as a thin line.
However, after toying with objects, I've discovered that
the bug is related to spheres and ellipsoids. A cube a couple
of thousand miles wide set at a quarter millon miles is visible
(as a pixel, granted, but still visible). A sphere, 6 k miles wide,
(assuming a pov unit is 1 meter) at 292 000 miles is not visible.
Why?
I have not been able to pinpoint the bug in the source. It
seems OK to me... still, it is not. My guess is that the epsilon
is used in an additive way instead of multiplicative way in
the sphere intersection routine (should be something like
eps * dist rather than just eps).
Best,
S.
> Don't try to be 100% accurate. Povray isn;t a physics real
> world modeler. its an Artistic Program. As long as it looks
> right to you then its accurate =}
> > 2. Scale your distances to fit within POV's current bounds. If your moon is 100x
closer and
> > 100x smaller, the error in parellax will be well under one pixel.
That's the best fix, but I dont like it
> >
> > Dan
--
----------------------------------------------------------
Steven Pigeon Ph. D. Student.
University of Montreal.
pig### [at] iroumontrealca Topics: data compression,
pig### [at] jspumontrealca signal processing,
ste### [at] researchattcom non stationnary signals
and wavelets.
----------------------------------------------------------
http://www.iro.umontreal.ca/~pigeon
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<snip>
>However, after toying with objects, I've discovered that
>the bug is related to spheres and ellipsoids. A cube a couple
>of thousand miles wide set at a quarter millon miles is visible
>(as a pixel, granted, but still visible). A sphere, 6 k miles wide,
>(assuming a pov unit is 1 meter) at 292 000 miles is not visible.
<snip>
Rather than a bug that only effects these shapes, could it not just be that
a sphere's image is less clear than a squares from the same distance? For
example, looking straight at at, a cube will show up as a solid, pretty much
evenly shaded square. A sphere will however be more of a brighter point
with dimmer edges around it. Perhaps, at these distances, it is the less
visible properties of the sphere that makes POV decide there's not enough
light to plot a pixel - unlike the cube, which may just have enough light
from it's apparently brighter side to appear as one.
Just my 2 pence :)
Matt
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Matthew Bennett wrote:
> <snip>
> >However, after toying with objects, I've discovered that
> >the bug is related to spheres and ellipsoids. A cube a couple
> >of thousand miles wide set at a quarter millon miles is visible
> >(as a pixel, granted, but still visible). A sphere, 6 k miles wide,
> >(assuming a pov unit is 1 meter) at 292 000 miles is not visible.
> <snip>
>
> Rather than a bug that only effects these shapes, could it not just be that
> a sphere's image is less clear than a squares from the same distance? For
> example, looking straight at at, a cube will show up as a solid, pretty much
> evenly shaded square. A sphere will however be more of a brighter point
> with dimmer edges around it. Perhaps, at these distances, it is the less
> visible properties of the sphere that makes POV decide there's not enough
> light to plot a pixel - unlike the cube, which may just have enough light
> from it's apparently brighter side to appear as one.
NO, I _did_ check for that. That was my first thought... then I set
the sphere's color to Yellow*2 on a black background... That should have
been enough...
>
>
> Just my 2 pence :)
>
> Matt
--
----------------------------------------------------------
Steven Pigeon Ph. D. Student.
University of Montreal.
pig### [at] iroumontrealca Topics: data compression,
pig### [at] jspumontrealca signal processing,
ste### [at] researchattcom non stationnary signals
and wavelets.
----------------------------------------------------------
http://www.iro.umontreal.ca/~pigeon
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Strangely enough, I can confirm this... I started with a sphere at the origin,
which I expanded appropriately as I moved it further out along the z-axis, and
when numbers got into the millions, it disappeared. A box, slightly further
out, remained visible...
-Mark R.
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Yep, the scale of things (distance, size) in POV-Ray is not infinite.
Others have brought this up before, one person in particular I can't
recollect since its been a year or more. But I tried my own scale
testing too and apparently the cone primitive is a very sturdy piece of
pov script. The sphere is one of the weakest, it changes size and
disappears altogether rather easily if scaled too large or small. The
box primitive tends to distort quite a bit before suffering the same
fate. This happens regardless of camera being scaled to view objects.
I could put my scale test file at the scene-files.text group if I can
locate it here.
Mark Radosevich wrote:
>
> Strangely enough, I can confirm this... I started with a sphere at the origin,
> which I expanded appropriately as I moved it further out along the z-axis, and
> when numbers got into the millions, it disappeared. A box, slightly further
> out, remained visible...
>
> -Mark R.
--
omniVERSE: beyond the universe
http://members.aol.com/inversez/POVring.htm
=Bob
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