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"Cousin Ricky" <rickysttATyahooDOTcom> wrote:
> Stephen <mca### [at] aol com> wrote:
> > I would have expected it to look as if the internals were rolling like a
> > hydrocarbon fire.
>
> A pyroclastic flow is not a hydrocarbon fire.
>
> ardentes. The glow is difficult to see in daylight, but I have seen it in video
> local news for me.) The edge of the flow, where it contacts the ground, looks
> like glowing embers.
Hi Ricky,
I think as with all things in nature not all can be classified into the one or
other category. I think the eruption with the following link is a mixture of a
pyroclastic flow and a magma eruption (and the most magnificent eruption I ever
found depicted):
http://upload.wikimedia.org/wikipedia/commons/1/17/MountRedoubtEruption.jpg
Best regards,
Michael
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> Hi folks,
>
> I hesitated a while to give you this image, since it is far away from being
> finished. It depicts a certain kind of volcanic eruption, a so called
> pyroclastic flow. That is an Eruption of a mixture of gases and ashes first
> described by Pliny the Younger who witnessed the downfall of Pompeji. I think
> the flow itself is looking good enough now - may be some play with the grays is
> needed for the "layers" of the media. But what to do with this empty areas? The
> scale of the image is a region of some 20 km^2 viewed at an altitude of 5 km.
> The mountain happens to be Mount Rainier near Seattle, since very detailed
> hight_field data are available at Georgia Tech. I modelled the flow - and
> especially his extend - after the hazard map given in the Wikipedia and pictures
> of other pyroclastic flows. The problem is the shear scale of the image. To have
> a tree recognizable I would have it 150 m high at least. I have no problem to
> scale things a little bit higher as they are in reallity, but 10 times? I will
> be thankful for every idea. My only one so far is, to look through the window of
> a plane, just to reduce the problem a little bit.
>
> If you understand German, the file name states some flaws with the ground flows
> I'm repairing at the moment but cannot be seen with this prespective.
>
> Best regards,
> Michael
>
Prety good so far.
I'd make the clouds much more dence and more to the white side.
As for the trees, at that scale, you only need the simplest, and small,
place holders: Small leaf green sphere and cones. Use a colour map of
greens and apply it the the bunch as a somewhat turbulated bozo
pattern... Just enough to suggest that there are actualy trees in the area.
Alain
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Alain <kua### [at] videotronca> wrote:
> > Hi folks,
> >
> > I hesitated a while to give you this image, since it is far away from being
> > finished. It depicts a certain kind of volcanic eruption, a so called
> > pyroclastic flow. That is an Eruption of a mixture of gases and ashes first
> > described by Pliny the Younger who witnessed the downfall of Pompeji. I think
> > the flow itself is looking good enough now - may be some play with the grays is
> > needed for the "layers" of the media. But what to do with this empty areas? The
> > scale of the image is a region of some 20 km^2 viewed at an altitude of 5 km.
> > The mountain happens to be Mount Rainier near Seattle, since very detailed
> > hight_field data are available at Georgia Tech. I modelled the flow - and
> > especially his extend - after the hazard map given in the Wikipedia and pictures
> > of other pyroclastic flows. The problem is the shear scale of the image. To have
> > a tree recognizable I would have it 150 m high at least. I have no problem to
> > scale things a little bit higher as they are in reallity, but 10 times? I will
> > be thankful for every idea. My only one so far is, to look through the window of
> > a plane, just to reduce the problem a little bit.
> >
> > If you understand German, the file name states some flaws with the ground flows
> > I'm repairing at the moment but cannot be seen with this prespective.
> >
> > Best regards,
> > Michael
> >
>
> Prety good so far.
>
> I'd make the clouds much more dence and more to the white side.
>
> As for the trees, at that scale, you only need the simplest, and small,
> place holders: Small leaf green sphere and cones. Use a colour map of
> greens and apply it the the bunch as a somewhat turbulated bozo
> pattern... Just enough to suggest that there are actualy trees in the area.
>
>
> Alain
Thanks again. I still am at this track since you propose a similiar approach as
Jaime gave with his Project Tierra. The textures I used are stemming from this
project I only modified them a little bit to allow for turbulence between them.
Jaime's original had very sharp transitions between the ice cap region and the
rocky parts e.g.. I simply used a warped texture between them. But he also used
dummy trees as I remember. To texture them with a greenish bozo pattern seems to
be a fresh and very fine idea. May be not only green but have an autumn
coloring. A wonderful suggestion.
Many thanks,
Michael
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"MichaelJF" <mi-### [at] t-onlinede> wrote:
> Hi Ricky,
>
> yes you are right completely. But as I learned so far Pliny's report is accepted
> nowadays. May be I'm wrong with that.
No, you are correct. Pliny's report /is/ accepted nowadays. But before the
exaggerated his observations.
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"MichaelJF" <mi-### [at] t-onlinede> wrote:
> http://upload.wikimedia.org/wikipedia/commons/1/17/MountRedoubtEruption.jpg
That! THAT! That volcano interfered with my job ca. 1990.
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On 18/07/2013 5:39 PM, Cousin Ricky wrote:
> Stephen <mca### [at] aolcom> wrote:
>> I would have expected it to look as if the internals were rolling like a
>> hydrocarbon fire.
>
> A pyroclastic flow is not a hydrocarbon fire.
I don't think that I said it was cuz.
But after watching the video Michael posted a link to. I thing billowing
is a better way of putting it. I was surprised that the cloud like
structure look very stable as it was moving at a fair percentage of the
speed of sound. About 25% roughly.
You tend to describe things in terms of what you know and I have seen a
lot of gas being flared off.
>
> ardentes. The glow is difficult to see in daylight, but I have seen it in video
> local news for me.) The edge of the flow, where it contacts the ground, looks
> like glowing embers.
I remember it it made the news here, in the UK, big time. Did you have
to evacuate?
--
Regards
Stephen
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On 18/07/2013 8:11 AM, MichaelJF wrote:
>
> Thank you Stephen, yes a magnifying would show the trees but I think it would be
> a bit disturbing to the scene.
>
Yes it would make it a bit like a newspaper article graphic.
>> How did you create the cloud?
>
> First I played with Rune's particle system to find a believable ground flow. If
> one finds the correct position and size of the emitter object it is fine to find
> the general direction of flows. But it has its limitations since the particles
> interact only with the mountain in this case and not with each other. Then I
> created ten layers of the cloud using the particles and for each cloud ist
> predecessors as the ground object in a modified version of Gilles Tran's
> makecloud2 macro (mainly allowing for different directions and using a gaussian
> distribution than his uniform). For his tomography I grouped them into four
> groups at the moment. The resulting df3-files were used as different media in
> the same box. Rendering time is now some 5 hours.
That is the fun bit, experimenting. :-)
If your media containers are the same size you can combine them into one
interior. I have done this to get colour by using red, green and blue
df3 files. Well three df3 files each with a different emission.
This might speed up the render if it is suitable to your scene.
> Take a look at this:
> http://www.maniacworld.com/erupting-volcano.htm
>
A sight indeed. To be enjoyed at a distance.
>> google have lots of white in them. But that is, I think, being very
>> critical.
>
> I don't think it very critical. I plan to work a little bit on the colors and
> the densities. May be I
> change the grouping of the clouds.
>
We await with interest.
--
Regards
Stephen
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Stephen <mca### [at] aolcom> wrote:
> I remember it it made the news here, in the UK, big time. Did you have
> to evacuate?
No, I live on a different island, about 300 km to the northwest. But we got
quite a bit of the ash.
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On 18-7-2013 20:01, MichaelJF wrote:
> I think as with all things in nature not all can be classified into the one or
> other category. I think the eruption with the following link is a mixture of a
> pyroclastic flow and a magma eruption (and the most magnificent eruption I ever
> found depicted):
> http://upload.wikimedia.org/wikipedia/commons/1/17/MountRedoubtEruption.jpg
True. The typical pyroclastic flow /sensu stricto/ runs along the
topographic slope of the mountain. The lighter ash goes upwards. While
the composition is identical, the pyroclastic flow is the coarser one
and also to be found at the base of a typical tephra deposits, covered
with an ash layer. They can show internal graded bedding but this is
often obscured by the gas turbulence and the high density of the whole
thing.
Thomas
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"Cousin Ricky" <rickysttATyahooDOTcom> wrote:
> Stephen <mca### [at] aolcom> wrote:
> > I remember it it made the news here, in the UK, big time. Did you have
> > to evacuate?
>
> No, I live on a different island, about 300 km to the northwest. But we got
> quite a bit of the ash.
Still a bit close.
We were almost neighbours, just after that. I was working in Jamaica in 1998.
Where I discovered PovRay
Stephen
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