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Hi all!
Here is a simple scene with photons and dispersion for a simple shape made
of glass. The dispersion coefficient is high (1.035) in order to produce a
desired exagerated effect.
I have one concern with this result: the shadow of the shape on the ground
does not seem to be anti-aliased. What's up?
I also see bandings and white spots near the Sphere/cylinder edge on the
shadow. Numerical artifacts for the latter, and too few photons for the
former?
The render time is about 1:15 hours, mainly taken by the shape, on Win, P4,
2.8 GHz for 1024*768 resolution.
The code is short so I can put it hereafter.
Comments and suggestions welcome.
Regards.
Bruno.
// Persistence of Vision Ray Tracer Scene Description File
// File: ?.pov
// Vers: 3.5
// Desc: Basic Scene Example
// Date: mm/dd/yy
// Auth: ?
//
#version 3.5;
#include "colors.inc"
#include "stones.inc"
global_settings {
assumed_gamma 1.0
max_trace_level 20
photons
{
spacing 0.003
}
}
// ----------------------------------------
camera {
location <0.0, 0.5, -4.0>
angle 50
right x*image_width/image_height
look_at <0.0, 0., 0.0>
}
sky_sphere {
pigment {
gradient y
color_map {
[0.0 rgb <0.6,0.7,1.0>]
[0.7 rgb <0.0,0.1,0.8>]
}
}
}
light_source {
<0, 0, 0> // light's position (translated below)
color rgb <1, 1, 1> // light's color
translate <-30, 35, 30>
photons
{
reflection on
refraction on
}
}
// ----------------------------------------
plane {
y, -1
pigment {rgb 0}
normal {bozo 0.5 scale 0.0001}
finish {specular 0.4 roughness 0.1}
}
merge
{
sphere {0, 1}
cylinder {0, 2*y, 0.25}
sphere {2*y, 0.3}
texture {
pigment {rgbt 1}
normal {bozo 0.75 scale 0.2}
finish{
specular 0.8 roughness 0.015
reflection {0.2, 0.5 fresnel}
conserve_energy
}
}
interior
{
ior 1.3
fade_color Green fade_power 1001 fade_distance 2
dispersion 1.035 dispersion_samples 30
}
photons
{
target 1
reflection on
refraction on
collect off
}
rotate 180*z
rotate 60*z
rotate -20*y
translate <-1, 0.5, 3>
//no_image
}
Post a reply to this message
Attachments:
Download 'photons_1.jpg' (174 KB)
Preview of image 'photons_1.jpg'
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Bruno Cabasson scripsit::
> Hi all!
>
> Here is a simple scene with photons and dispersion for a simple shape made
> of glass. The dispersion coefficient is high (1.035) in order to produce a
> desired exagerated effect.
>
> I have one concern with this result: the shadow of the shape on the ground
> does not seem to be anti-aliased. What's up?
>
Ponctual light do not produce soft-shadow. you would need an
area_light for that kind of effect.
> I also see bandings and white spots near the Sphere/cylinder edge on the
> shadow. Numerical artifacts for the latter, and too few photons for the
> former?
>
I do not know. may be it's just how it would be in reality...
> The render time is about 1:15 hours, mainly taken by the shape, on Win, P4,
> 2.8 GHz for 1024*768 resolution.
>
> The code is short so I can put it hereafter.
Thanks!
>
> Comments and suggestions welcome.
>
> Regards.
--
Eifersucht ist die Leidenschaft, die mit Eifer sucht, was Leiden
schafft.
Eco: -8.75 Soc: -6.72
http://www.politicalcompass.org/
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> Bruno Cabasson scripsit::
> >
> > I have one concern with this result: the shadow of the shape on the ground
> > does not seem to be anti-aliased. What's up?
>
Le Forgeron <jgr### [at] free fr> wrote:
> Ponctual light do not produce soft-shadow. you would need an
> area_light for that kind of effect.
That doesn't explain the aliasing, though. With proper anti-aliasing and no
area light, the shadow should have a sharp, but smooth edge. (An area light
will almost certainly bypass the aliasing problem, but you will pay a lot
more than an hour 15.)
My first thought was too high an antialias_threshold value, but the green
part of the sphere has subtler tones than the shadow, yet it looks fine.
Post a reply to this message
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"Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> wrote:
>
> I have one concern with this result: the shadow of the shape on the ground
> does not seem to be anti-aliased. What's up?
It's two things.
1. The threshold *is* too high. Set Antialias_Threshold to 0.02, or use
+A0.02. (Most scenes won't need it this low, but this scene does.) I also
figured out the reason why the glass seemed antialiased but not the shadow:
the dispersion! As the light spread out inside the glass, it automatically
fudged the aliasing artifacts.
2. Ooh, i almost forgot. Use +AM2. Never mind that, just add
Sampling_Method=2 to your povray.ini file and be done with it.
Post a reply to this message
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I just wanted to say that megapov did an amazing job with your scenefile
Scene Statistics
Finite objects: 1
Infinite objects: 1
Light sources: 1
Total: 3
Render Statistics
Image Resolution 1280 x 1024
----------------------------------------------------------------------------
Pixels: 1310720 Samples: 1537600 Smpls/Pxl: 1.17
Rays: 136549780 Saved: 20564619 Max Level: 14/20
----------------------------------------------------------------------------
Ray->Shape Intersection Tests Succeeded Percentage
----------------------------------------------------------------------------
Cone/Cylinder 166648224 27585342 16.55
CSG Merge 166648224 83774023 50.27
Plane 166648224 62594811 37.56
Sphere 333296448 94246382 28.28
----------------------------------------------------------------------------
Calls to Noise: 363233664 Calls to DNoise: 10
----------------------------------------------------------------------------
Shadow Ray Tests: 101326126 Succeeded: 20222013
Reflected Rays: 63552010 Total Internal: 11697850
Refracted Rays: 70582748
----------------------------------------------------------------------------
Number of photons shot: 877422
Surface photons stored: 12373426
Priority queue insert: 106559764
Priority queue remove: 20567750
Gather function called: 14882980
----------------------------------------------------------------------------
Smallest Alloc: 20 bytes
Largest Alloc: 327696 bytes
Peak memory used: 248589212 bytes
Total Scene Processing Times
Parse Time: 0 hours 0 minutes 0 seconds (0 seconds)
Photon Time: 0 hours 2 minutes 22 seconds (142 seconds)
Cloth Time: 0 hours 0 minutes 0 seconds (0 seconds)
Mechsim Time: 0 hours 0 minutes 0 seconds (0 seconds)
Render Time: 0 hours 5 minutes 8 seconds (308 seconds)
Postpr. Time: 0 hours 0 minutes 0 seconds (0 seconds)
Total Time: 0 hours 7 minutes 30 seconds (450 seconds)
On a MacBook Pro 2.16 GHz Intel Core Duo.
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"Cousin Ricky" <ric### [at] yahoocom> wrote:
> "Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> wrote:
> >
> > I have one concern with this result: the shadow of the shape on the ground
> > does not seem to be anti-aliased. What's up?
>
> It's two things.
>
> 1. The threshold *is* too high. Set Antialias_Threshold to 0.02, or use
> +A0.02. (Most scenes won't need it this low, but this scene does.) I also
> figured out the reason why the glass seemed antialiased but not the shadow:
> the dispersion! As the light spread out inside the glass, it automatically
> fudged the aliasing artifacts.
>
> 2. Ooh, i almost forgot. Use +AM2. Never mind that, just add
> Sampling_Method=2 to your povray.ini file and be done with it.
OK. After following these advises, I found that the aa threshold is
responsible for the (apparent) non anti-aliasing. I was persuaded that the
'constrast' between the shadow and the ground was OK for 0.3. The value 0.1
is enough. +AM2 is not necessary.
Another concern now: when I turn photons off by commenting out the photons{}
block in global_settings{} the shadow has a green color, which may seem
normal because the material is green (see picture). Why then, when photons
are on, does the shadow not inherit the green color of the glass?
Regards
Post a reply to this message
Attachments:
Download 'photons_2.jpg' (75 KB)
Preview of image 'photons_2.jpg'
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Bruno Cabasson nous apporta ses lumieres en ce 11/09/2006 05:28:
> "Cousin Ricky" <ric### [at] yahoocom> wrote:
>> "Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> wrote:
>>> I have one concern with this result: the shadow of the shape on the ground
>>> does not seem to be anti-aliased. What's up?
>> It's two things.
>>
>> 1. The threshold *is* too high. Set Antialias_Threshold to 0.02, or use
>> +A0.02. (Most scenes won't need it this low, but this scene does.) I also
>> figured out the reason why the glass seemed antialiased but not the shadow:
>> the dispersion! As the light spread out inside the glass, it automatically
>> fudged the aliasing artifacts.
>>
>> 2. Ooh, i almost forgot. Use +AM2. Never mind that, just add
>> Sampling_Method=2 to your povray.ini file and be done with it.
>
> OK. After following these advises, I found that the aa threshold is
> responsible for the (apparent) non anti-aliasing. I was persuaded that the
> 'constrast' between the shadow and the ground was OK for 0.3. The value 0.1
> is enough. +AM2 is not necessary.
>
> Another concern now: when I turn photons off by commenting out the photons{}
> block in global_settings{} the shadow has a green color, which may seem
> normal because the material is green (see picture). Why then, when photons
> are on, does the shadow not inherit the green color of the glass?
>
> Regards
>
>
> ------------------------------------------------------------------------
>
Without photons, the shadow ignore the ior of the object, so the shadow is
completely illuminated by the filtered light. It's a little like the onject was
only a coloured empty shell. This is unrealistic.
With photons, the light don't reatch the shadowed area, only the photons do.
It's what apens in the real world, and what you would see if you where outside
on the moon: a totaly dark shadow only illuminated by the diffracted light.
--
Alain
-------------------------------------------------
Documentation; The worst part of programming.
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