I've given this some thought and I suggest using a normal in the camera
statement, with a pattern like ripples being oriented in relation to
where the meteor path line of sight is at.  Might take a normal map of
some ingenious design to accomplish.
Well, maybe not ingenious, however here's something I tried just now.

Bob

/* example of creating shockwave in air (no vapor) */

global_settings {
        number_of_waves 0
}

#declare Amplitude=0.333; // amount of shockwave effect
#declare Frequency=6; // number of peaks and troughs
#declare xSize=0.5; // lengthwise curvature (or size)
#declare zSize=0.25; // crosswise curvature (more curve when less than
xSize)
#declare xPos=-2; // move ripples off-center
#declare Width=0.45; // pie-slice region of air displacement (<1.0 but
>0.5)
#declare EntryAngle=-30; // angle of attack
#declare Placement=<0.25,-0.075,0>; // offset from center, small values
of x and y (no z)

#declare N0=normal {ripples 0} // dummy normal
#declare N1=normal {ripples Amplitude frequency Frequency scale
<xSize,1,zSize> translate xPos*x}

camera {
        location 0
        look_at 1*z
        normal {radial normal_map {
                [Width N0][0.5 N1][1-Width N0]
        } ramp_wave rotate 90*x
         rotate EntryAngle*z translate Placement}
}

light_source {<10,10,-10>, 1}

sphere {0,1
        pigment {gradient y color_map {
                [0 color rgb <.9,.6,.3>]
                [.1 color rgb <.6,.3,.6>]
                [.3 color rgb <.4,.6,.8>]
                [.6 color rgb <.2,.4,.6>]
        }}
       finish {ambient .5}
    scale 1000
}

// meteor (test object: note that this really messes up if shockwave is
intense)
cone {-x,1,0,.1 scale <100,10,10>
        pigment {granite color_map {
                [0 color rgb <.9,.8,.7>]
                [1 color rgb <.7,.6,.4>]
        }}
       finish {ambient .75}
     rotate EntryAngle*z translate <25,-5,100> // placing this is only a
guess
 no_shadow
}

"kane" <ann### [at] mindspringcom> wrote in message
news:392b3ffd@news.povray.org...
|     I'm trying to create the disturbance to the atmosphere as a meteor
| passes through it. Kind of like ripples in the air, that sort of
thing. Is
| there any way in Pov or MegPov to do this?

Post a reply to this message

"Mike Williams" <mik### [at] nospamplease> wrote in message
news:JOt### [at] econymdemoncouk...


> A bigger problem is that very few people (if any) have ever observed
> atmospheric disturbances caused by meteors, so it's going to be hard to
> check whether the rendering is remotely realistic. None of the meteors
> that I've seen have caused any observable atmospheric disturbances.

It seems to me that you would have to be pretty darn close to the meteor to
actually see the shockwave, and if you were that close, your ability to see
it would still depend on several other factors: 1) Light; 2) Atmospheric
conditions; 3) The limits of human field-of-vision in tracking, at close
range, an object moving at supersonic speed; 4) The natural tendency to
duck.

I do have an mpeg of a condensation ring forming around a jet as it attains
the speed of sound. It is, of necessity, short.

--
simon.A

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SamuelT wrote:

> Wouldn't the isosurface give sharp edges?
>

I was thinking of an isosurface with very thin edges (with no ripples) and a thick
center (with the ripples). No, I don't have the equation...
G.

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Hmm, it could be done, but it would have to face the camera, probably. Hmm.....

Gilles Tran wrote:

> SamuelT wrote:
>
> > Wouldn't the isosurface give sharp edges?
> >
>
> I was thinking of an isosurface with very thin edges (with no ripples) and a thick
> center (with the ripples). No, I don't have the equation...
> G.

--
Samuel Benge

E-Mail: STB### [at] aolcom

Visit my isosurface tutorial at http://members.aol.com/stbenge

Post a reply to this message

kane wrote:

>     I'm trying to create the disturbance to the atmosphere as a meteor
> passes through it. Kind of like ripples in the air, that sort of thing. Is
> there any way in Pov or MegPov to do this?

My ParticlePatch, which I just released (see p.u.p/p.p) may be able to help

Post a reply to this message

I tried it, and it worked. The fully-transparent isosurface bent light to greater
degrees towards it's middle. Problem was the edges of the isosurface showed a bit. I
couldn't get rid of the refracted dark lines of the isosurface container. Still, it
rendered in good time (compared to multiple objects of varying degrees of refraction).



Gilles Tran wrote:

> SamuelT wrote:
>
> > Wouldn't the isosurface give sharp edges?
> >
>
> I was thinking of an isosurface with very thin edges (with no ripples) and a thick
> center (with the ripples). No, I don't have the equation...
> G.

--
Samuel Benge

E-Mail: STB### [at] aolcom

Visit my isosurface tutorial at http://members.aol.com/stbenge

Post a reply to this message

Mike Williams wrote in message ...
>Wasn't it SamuelT who wrote:

>The shockwaves produced by a meteor travelling at hypersonic velocity
>will actually have sharp edges, so that shouldn't be a problem.
>
>A bigger problem is that very few people (if any) have ever observed
>atmospheric disturbances caused by meteors, so it's going to be hard to
>check whether the rendering is remotely realistic. None of the meteors
>that I've seen have caused any observable atmospheric disturbances.
>


What about the comet that hit Jupiter a few years ago. I remrember some nice
pics (obviously not close up )

Gail
********************************************************************
* gsh### [at] monotixcoza              * Reality.dat not found         *
* http://www.rucus.ru.ac.za/~gail/ * Attempting to reboot universe *
********************************************************************
* The best way to accelerate Windows NT is at 9.8 m/s^2      *
********************************************************************

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Here's my idea on it again.  Squeezed in a place for the meteor/asteroid trail. And I
noticed a small mistake before anyhow.

/* example of creating shockwave in air (faked refractive type thing only).
Just a simple way, nothing much mathematical here  ;-) */

global_settings {
        number_of_waves 0
}

#declare Amplitude=0.1; // amount of shockwave effect
#declare Frequency=6; // number of peaks and troughs
#declare xSize=0.5; // lengthwise curvature (or size)
#declare zSize=0.25; // crosswise curvature (more curve when less than xSize)
#declare xPos=-2; // move ripples off-center
#declare Width=0.333; // pie-slice region of air displacement (<0.475 and >=0)
#declare EntryAngle=-30; // angle of attack
#declare Placement=<0.25,0.025,0>; // offset from center, small values of x and y (no
z)

#declare N0=normal {ripples 0} // dummy normal
#declare N1=normal {ripples Amplitude frequency Frequency scale <xSize,1,zSize>
translate xPos*x}

camera {
        location -z
        look_at +z
        normal {radial normal_map {
                [Width N0][0.45 N1][0.495 N0][0.505 N0][0.55 N1][1-Width N0]
        } ramp_wave rotate 90*x
         rotate EntryAngle*z translate Placement}
}

// test for center of normal in camera
// sphere {<0.25,-0.075,0>,.05 pigment {color green 1} finish {ambient 1}}

light_source {<-9,90,-900>, <.5,.4,.3>}

// sky
sphere {0,1
        pigment {gradient y color_map {
                [0 color rgb <.9,.6,.3>]
                [.1 color rgb <.7,.3,.4>]
                [.3 color rgb <.3,.6,.8>]
                [.6 color rgb <.2,.4,.6>]
        }}
       finish {ambient .5}
    scale 1000
}

// ground
plane {y,-5
        pigment {spotted color_map {
                [0 color rgb <.5,.9,.6>]
                [1 color rgb <.6,.7,.3>]
        } scale 5}
       finish {ambient .25 diffuse .7 phong .2 phong_size 20}
}

// meteor (test object: note that this really messes up if shockwave is intense)
union {
light_source {.1*x, <.99,.67,.33>*1.5}
 sphere {0,.4 scale <15,10,10>}
 cone {-x,1.1,0,.1 scale <111,10,10>}
        pigment {granite color_map {
                [0 color rgb <1.2,.9,.5>*1.5]
                [1 color rgb <.9,.4,.1>]
        } scale 15}
       finish {ambient .85 metallic brilliance 3}
     rotate EntryAngle*z
      rotate 5*z translate <25,2.5,100> // only a guess here
 no_shadow
}

Post a reply to this message

This brings to mind a good suggestion for a feature: Variable ior in media;
kind of like a ior_map. AFAIK, the ior of any object in the present versions
is constant, and in thus light won't be bent when inside an object; no
matter what media-settings exist. But if one could specify the ior along
with for example the density of the media, Povray should be able to
callulate refraction based on the current ior and the ior ahead of the
samplig ray. But this again assumes that media is sampled linarily, and that
is not trur with all types, is it?

Simen Kvaal.

kane skrev i meldingen <392b3ffd@news.povray.org>...
>    I'm trying to create the disturbance to the atmosphere as a meteor
>passes through it. Kind of like ripples in the air, that sort of thing. Is
>there any way in Pov or MegPov to do this?
>
>

Post a reply to this message

Simen Kvaal wrote:
> 
> This brings to mind a good suggestion for a feature: Variable ior in media;
> kind of like a ior_map.

I believe this would be possible, indeed it has been suggested before. But I
suspect it would be extremely slow, slower than scattering media, because the
calculations involved become significantly more complex.

-- 
Margus Ramst

Personal e-mail: mar### [at] peakeduee
TAG (Team Assistance Group) e-mail: mar### [at] tagpovrayorg

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