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On 26-2-2019 19:48, MichaelJF wrote:
> Am 26.02.2019 um 11:15 schrieb Thomas de Groot:
>> On 24-2-2019 20:20, MichaelJF wrote:
>>> Hi Thomas,
>>> this time a didn't click accidentally into the image while converting
>>> it to jpg with the GIMP, but with purpose. In the marked area you can
>>> see the sharp edges I mean. The code was
>>>
>>> #if(SteamFog)
>>> #declare DensBoden1= density {
>>> agate
>>> agate_turb 1
>>> density_map {
>>> [ 0 rgb <1,1,1>/5 ]
>>> //[ 0.02 rgb <1,1,1> ]
>>> [ 0.03 rgb <0,0,0> ]
>>> [ 1 rgb <0,0,0> ]
>>> }
>>> }
>>>
>>> #declare DensBoden3= density {
>>> agate
>>> agate_turb 1
>>> density_map {
>>> [ 0 rgb <1,1,1>/5 ]
>>> //[ 0.02 rgb <1,1,1> ]
>>> [ 0.02 rgb <0,0,0> ]
>>> [ 1 rgb <0,0,0> ]
>>> }
>>> scale <5,50,5>
>>> //warp { turbulence <0.5,0.1,0.5> }
>>> //rotate <0,90,0>
>>> }
>>>
>>> #declare DensLuft = density {
>>> rgb <0,0,0>
>>> }
>>> box { <-150,0.001,-15>,<150.01,1,150> pigment { rgbt 1 } hollow
>>> interior {
>>> media {
>>> scattering { 2, White/5 }
>>> //absorption <0,0.25,1>
>>> //intervals 25
>>> samples 64
>>> density {
>>> gradient y
>>> density_map {
>>> [ 0 DensBoden1 ]
>>> [ 0.5 DensBoden1 ]
>>> [ 0.6 DensLuft ]
>>> [ 1 DensLuft ]
>>> }
>>> scale <1,2,1> translate <0,-0.5,0> // avoid
>>> repetition at height 1
>>> warp { turbulence <0.01,0.4,0.01> }
>>> }
>>> }
>>> media {
>>> scattering { 2, White/5 }
>>> //absorption <0,0.25,1>
>>> //intervals 25
>>> samples 64
>>> density {
>>> gradient y
>>> density_map {
>>> [ 0 DensBoden3 ]
>>> [ 0.5 DensBoden3 ]
>>> [ 0.6 DensLuft ]
>>> [ 1 DensLuft ]
>>> }
>>> scale <1,2,1> translate <0,-0.5,0> // avoid
>>> repetition at height 1
>>> warp { turbulence <0.01,0.3,0.01> }
>>> }
>>> }
>>> #if(GlobalFog)
>>> media { scattering {2, White/5 } density { rgb 0.001 } }
>>> #end
>>> }
>>> }
>>> #if(GlobalFog)
>>> box { <-100,1.001,-5.9>,<100,25,130> pigment { rgbt 1} hollow
>>> interior {
>>> media { scattering {2, White/5 } density { rgb 0.0001 } }
>>> }
>>> }
>>> #end
>>> #end
>>>
>>> GlobalFog was activated. May be I have overlooked some thing or the
>>> other.
>>>
>>
>> My first tests of your code confirms me that the sharp edge is the
>> result of the container boundary, not of any different behaviour of
>> density.
>>
>> I want to test different options yet.
>>
> Hm,
> the problem seems to be within the second media statement (the first
> produces some ground noise only). The container boundary is at level y=1
> (y is up here). The transition between DensBoden3 and DensLuft(=nothing)
> is between 0.5 and 0.6 scaled to 1 and 1.2 but then translated to 0.5
> and 0.7 which is beneath the container boundary for sure.
>
I have yet to test the second media I confess. ;-)
Something interesting to do [hint] is to put the density scale /after/
the warp{turbulence}. Makes things a bit complicated but worth the
experiment.
--
Thomas
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On 26-2-2019 19:48, MichaelJF wrote:
> Hm,
> the problem seems to be within the second media statement (the first
> produces some ground noise only). The container boundary is at level y=1
> (y is up here). The transition between DensBoden3 and DensLuft(=nothing)
> is between 0.5 and 0.6 scaled to 1 and 1.2 but then translated to 0.5
> and 0.7 which is beneath the container boundary for sure.
>
Ok. I think I got it. The solution seems to be really simple. In both
media's density maps change:
density_map {
[ 0 DensBoden1 ]
[ 0.45 DensBoden1 ] //original: 0.5
[ 0.55 DensLuft ] //original: 0.6
[ 1 DensLuft ]
}
density_map {
[ 0 DensBoden3 ]
[ 0.45 DensBoden3 ] //original: 0.5
[ 0.55 DensLuft ] //original: 0.6
[ 1 DensLuft ]
}
That is all. If you want to increase the diffuseness, you can always
increase the distance between the two values, e.g. 0.35 --> 0.55. But I
would advise not to go higher than approximately 0.55.
--
Thomas
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A small test image with the corrected settings. What appears to be the
horizon is in reality the semitransparent bounding box, the camera being
situated just a tiny bit above it. The mist strands do not touch that
upper boundary but be aware that their extension upward is controlled by
the warp{turbulence} of 0.4 for the y-direction. So, it is a bit tricky
to find the correct values for the density map without the strands
piercing the container.
Samples may be a bit low as there are some artifacts visible but I
wouldn't change it as in your scene they would be hidden by the water
texture.
I have used here a somewhat denser scattering colour and also scattering
mode 5 which I often prefer, here with excentricity 0.5.
For this small scene, render time was about 30 minutes.
--
Thomas
Post a reply to this message
Attachments:
Download 'media mist_test.png' (245 KB)
Preview of image 'media mist_test.png'
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MichaelJF wrote on 22/02/2019 20:04:
> Hi to the crowd,
>
> this image has still a lot of flaws (sun colour and reflections, the
> swan model itself, textures of the cattails) and may be limitations to
> media by POV. media seems to be handling color_maps or density_maps
> different than pigment or texture having no interpolation between the
> map entries but shap edges. This is what I derived in a first attempt.
> Rendering time was a little bit longer (3 weeks).
>
> Best regards
> Michael
>
A beautiful and peacefulness image!
Perhaps the cane thicket at bottom right are too bright. And it might be
nice to see birds flying in the distance.
;-)
Paolo
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Le 19-02-27 à 03:55, Thomas de Groot a écrit :
> A small test image with the corrected settings. What appears to be the
> horizon is in reality the semitransparent bounding box, the camera being
> situated just a tiny bit above it. The mist strands do not touch that
> upper boundary but be aware that their extension upward is controlled by
> the warp{turbulence} of 0.4 for the y-direction. So, it is a bit tricky
> to find the correct values for the density map without the strands
> piercing the container.
>
> Samples may be a bit low as there are some artifacts visible but I
> wouldn't change it as in your scene they would be hidden by the water
> texture.
>
> I have used here a somewhat denser scattering colour and also scattering
> mode 5 which I often prefer, here with excentricity 0.5.
>
> For this small scene, render time was about 30 minutes.
>
When using turbulence, a rule of thumb is to assume that the area gets
enlarged by the turbulence value.
If you use turbulence 0.4, then, what was at 1 should be assumed to get
displaced between 0.6 and 1.4, and up to 2 for turbulence 1.
Post a reply to this message
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Am 27.02.2019 um 09:55 schrieb Thomas de Groot:
> A small test image with the corrected settings. What appears to be the
> horizon is in reality the semitransparent bounding box, the camera being
> situated just a tiny bit above it. The mist strands do not touch that
> upper boundary but be aware that their extension upward is controlled by
> the warp{turbulence} of 0.4 for the y-direction. So, it is a bit tricky
> to find the correct values for the density map without the strands
> piercing the container.
>
> Samples may be a bit low as there are some artifacts visible but I
> wouldn't change it as in your scene they would be hidden by the water
> texture.
>
> I have used here a somewhat denser scattering colour and also scattering
> mode 5 which I often prefer, here with excentricity 0.5.
>
> For this small scene, render time was about 30 minutes.
>
Hello Thomas,
many, many thanks for your efforts and for solving this problem. I was
on the wrong track. There is another issue with media and sharp edges I
experienced playing around with the emitting media simulating the sun in
this image and expected a similiar problem with the fog. But these two
problems are different issues completely. As Alain confirms your results
one has to consider the amount of turbulence while calculating the
scaling of the media or the boundaries of the container object
additionally.
I will depict the other issue ASAP. At the moment it is at 39% after
some 5 hours of rendering. In this case the container cannot prove a
problem since it is much larger than the media and a box and not a
sphere. I fear it is one of the problems arising from the prescision
settings within POV to deal with the trade off between precision and
rendering time.
Best regards
Michael
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Am 27.02.2019 um 11:25 schrieb Paolo Gibellini:
> MichaelJF wrote on 22/02/2019 20:04:
>> Hi to the crowd,
>>
>> this image has still a lot of flaws (sun colour and reflections, the
>> swan model itself, textures of the cattails) and may be limitations to
>> media by POV. media seems to be handling color_maps or density_maps
>> different than pigment or texture having no interpolation between the
>> map entries but shap edges. This is what I derived in a first attempt.
>> Rendering time was a little bit longer (3 weeks).
>>
>> Best regards
>> Michael
>>
> A beautiful and peacefulness image!
> Perhaps the cane thicket at bottom right are too bright. And it might be
> nice to see birds flying in the distance.
> ;-)
> Paolo
Many thanks Paolo,
it is a first WIP to demonstrate my idea how one can model steam fog
with POV. And as you can see from the discussion here it is far away
from being ready. I will consider your idea of birds in the distance. I
simply could copy them from another picture I made in the past where I
had a formation of cranes in the far distance. But first I would prefer
a more realistic sunrise with a better sky sphere and a better simulated
sun.
Best regards
Michael
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On 27-2-2019 17:39, Alain wrote:
> Le 19-02-27 à 03:55, Thomas de Groot a écrit :
>> A small test image with the corrected settings. What appears to be the
>> horizon is in reality the semitransparent bounding box, the camera
>> being situated just a tiny bit above it. The mist strands do not touch
>> that upper boundary but be aware that their extension upward is
>> controlled by the warp{turbulence} of 0.4 for the y-direction. So, it
>> is a bit tricky to find the correct values for the density map without
>> the strands piercing the container.
>>
>> Samples may be a bit low as there are some artifacts visible but I
>> wouldn't change it as in your scene they would be hidden by the water
>> texture.
>>
>> I have used here a somewhat denser scattering colour and also
>> scattering mode 5 which I often prefer, here with excentricity 0.5.
>>
>> For this small scene, render time was about 30 minutes.
>>
>
> When using turbulence, a rule of thumb is to assume that the area gets
> enlarged by the turbulence value.
>
> If you use turbulence 0.4, then, what was at 1 should be assumed to get
> displaced between 0.6 and 1.4, and up to 2 for turbulence 1.
Exactly! Thanks for the precision given. This was one of the reasons why
I gave the hint to try to put the scaling /after/ the warp {turbulence}.
I didn't pursue that path too far though.
--
Thomas
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I commented the steam fog approximation out, so it rendered a little bit
faster. One sees two instances of the same object (it is the example
from the tutorials shipped with POV but in a box {-2,2 } instead of a
sphere). The only difference is
object { Sonne
scale <500,500,500>*5
translate MediaPos
}
object { Sonne
translate <3,1,5>
}
with MediaPos=< 649.685959 , 1442.616855 , 39968.697311 >
Obviously I will not use it in my scene. It's just a riddle I
encountered by chance. I played a little bit with intervals, samples,
variance, confidence but without any success. It seems to be due to the
scaling alone.
Best regards
Michael
Post a reply to this message
Attachments:
Download 'twoinstancesofaemittingmedia.jpg' (555 KB)
Preview of image 'twoinstancesofaemittingmedia.jpg'
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On 28-2-2019 19:25, MichaelJF wrote:
> I commented the steam fog approximation out, so it rendered a little bit
> faster. One sees two instances of the same object (it is the example
> from the tutorials shipped with POV but in a box {-2,2 } instead of a
> sphere). The only difference is
>
> object { Sonne
> scale <500,500,500>*5
> translate MediaPos
> }
>
> object { Sonne
> translate <3,1,5>
> }
>
> with MediaPos=< 649.685959 , 1442.616855 , 39968.697311 >
>
> Obviously I will not use it in my scene. It's just a riddle I
> encountered by chance. I played a little bit with intervals, samples,
> variance, confidence but without any success. It seems to be due to the
> scaling alone.
>
My immediate reaction to this would be: "Did you take the scaling into
account in the media build of Sonne?"
You need to do the following /essential/ operation, for the first
instance, concerning the emission and, if applicable, scattering and
absorption:
#local MediaScale = <500, 500, 500>*5;
sphere {<0,0,0>, 1 //or a box of course
hollow
pigment {rgbt 1}
interior {
media {
samples 50
emission <0.8, 0.8, 0.8>/MediaScale
scattering {1, rgb <0.1, 0.1, 0.1>/MediaScale}
density {
spherical
density_map {
[0.20 rgb 0.0]
[1.00 rgb 1.0]
}
}
}
}
scale MediaScale
}
This is explained in the docs btw in 2.3.7.5 Media and transformations.
I think that lies at the root of your problem.
--
Thomas
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