Hello.

I've got a bunch of satellit pictures like this one
http://foo.buvette.org/trucs/nuages.jpeg and I want
use them to make an animation of the earth.

How can I process this pics to make them usable as
an image_map ?

Th.

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tcgetattr wrote:
> Hello.
> 
> I've got a bunch of satellit pictures like this one
> http://foo.buvette.org/trucs/nuages.jpeg and I want
> use them to make an animation of the earth.
> 
> How can I process this pics to make them usable as
> an image_map ?

I think that i need this sort of pictures :
http://earthobservatory.nasa.gov/Features/BlueMarble/BlueMarble_monthlies.php

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"tcgetattr" <tg### [at] getattrinvalid> wrote in message 
news:4aead916$1@news.povray.org...
> Hello.
>
> I've got a bunch of satellit pictures like this one
> http://foo.buvette.org/trucs/nuages.jpeg and I want
> use them to make an animation of the earth.
>
> How can I process this pics to make them usable as
> an image_map ?
>
> Th.

POV-Ray supports jpeg as an image_map format, so strictly speaking you don't 
need to process them at all to make them usable in POV-Ray. If you simply 
wish to animate the image sequence and generate an mpeg then you don't 
really even need to use POV-Ray. You can just use an mpeg compressor to 
assemble the sequence. Indeed POV-Ray won't automatically assemble an 
animation, it'll just create the individual frames, so you'll still need 
software to assemble the sequence into an animation.

If you want to do something more sophisticated, then any advice will really 
depend upon exactly what you want to do. If you want to do color correction, 
then you may be able to use a color_map with the image. If you want to 
project it onto a sphere and rotate the sphere, then you may need to 
assemble a mosaic of images (which you probably won't have if the images are 
from a geostationary satellite). If you want to overlay the clouds on a 
terrain map or over a visible light spectrum image then you may need to 
marry up the projections used (depending on the technical accuracy you are 
hoping to achieve).

So more information on what you are trying to achieve is needed to be able 
to offer any detailed advice.

Regards,
Chris B.
(ps Nice jeans.gif)

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"tcgetattr" <tg### [at] getattrinvalid> wrote in message 
news:4aeae4a5@news.povray.org...
> tcgetattr wrote:
>> Hello.
>>
>> I've got a bunch of satellit pictures like this one
>> http://foo.buvette.org/trucs/nuages.jpeg and I want
>> use them to make an animation of the earth.
>>
>> How can I process this pics to make them usable as
>> an image_map ?
>
> I think that i need this sort of pictures :
> http://earthobservatory.nasa.gov/Features/BlueMarble/BlueMarble_monthlies.php

There are some immediate problems apparent with this that could make life a 
little complicated. I'll just start throwing a couple of ideas in the air to 
get things started:

The cloud image you have only covers a small part of the planet whereas the 
BlueMarble images cover the whole planet, so, unless you have images from 
other multiple geostationary positions (or unless it's not stationary) then 
you can't cover the entire globe. If you do have other images then you have 
the problem of mosaic'ing them together.

Mapping the cloud cover image precisely to the projection of the BlueMarble 
images is likely to be tricky (if you need to do that). You may be able to 
get something approximate by using your cloud images with a flat projection 
onto a sphere and then using a spherical camera in the middle of the sphere 
to generate an image that would approximately overlay the BlueMarble images. 
If you want to overlay the clouds onto the BlueMarble images you could 
probably achieve this with a single pass in POV-Ray by using a spherical 
projection to project a BlueMarble image onto a slightly larger sphere that 
would show up as being behind the cloud sphere when the camera is in the 
middle of the two concentric spheres.

You could maybe use a filter on the image to  make the darker green parts 
transparent so that you could overlay the image onto a BlueMarble image (if 
you need to overlay the images). This could be done in an external graphics 
editor (e.g. Photoshop). If you wish to add tranparency that POV-Ray can use 
then you'll probably need to convert the cloud images into one of the 
formats that the filter option on the image_map supports (e.g. png or gif).

Regards,
Chris B.

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Chris B wrote:

>> I've got a bunch of satellit pictures like this one
>> http://foo.buvette.org/trucs/nuages.jpeg and I want
>> use them to make an animation of the earth.
>> How can I process this pics to make them usable as
>> an image_map ?

> need to assemble a mosaic of images (which you probably won't have if 
> the images are from a geostationary satellite). If you want to overlay 
    ...
> So more information on what you are trying to achieve is needed to be 
> able to offer any detailed advice.

   I think I have to do some geometric transformation on my pics
   to make them suitable for image mapping them.

> (ps Nice jeans.gif)

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tcgetattr <tg### [at] getattrinvalid> wrote:
>    I think I have to do some geometric transformation on my pics
>    to make them suitable for image mapping them.

  What kind of geometric transformation? POV-Ray already supports some.

-- 
                                                          - Warp

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Chris B wrote:
> 
>>> I've got a bunch of satellit pictures like this one
>>> http://foo.buvette.org/trucs/nuages.jpeg and I want
>>> use them to make an animation of the earth.
>>
>> I think that i need this sort of pictures :
>> http://earthobservatory.nasa.gov/Features/BlueMarble/BlueMarble_monthlies.php 
>>
> The cloud image you have only covers a small part of the planet whereas 
> the BlueMarble images cover the whole planet, so, unless you have images 
> from other multiple geostationary positions (or unless it's not 

   I'm a poor man, I only have one geostat satellite ;)

> Mapping the cloud cover image precisely to the projection of the 
> BlueMarble images is likely to be tricky (if you need to do that).

   You hit the real point here... I'm seeking for that mapping.

   http://foo.buvette.org/trucs/geostatpics.tar.gz (6 Mo)

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tcgetattr wrote:

> 
>   You hit the real point here... I'm seeking for that mapping.

   First try...
   http://foo.buvette.org/trucs/corrected.jpg

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"tcgetattr" <tg### [at] getattrinvalid> wrote in message 
news:4aeaf65b$2@news.povray.org...
> Chris B wrote:
>>
>>>> I've got a bunch of satellit pictures like this one
>>>> http://foo.buvette.org/trucs/nuages.jpeg and I want
>>>> use them to make an animation of the earth.
>>>
>>> I think that i need this sort of pictures :
>>> http://earthobservatory.nasa.gov/Features/BlueMarble/BlueMarble_monthlies.php
>> The cloud image you have only covers a small part of the planet whereas 
>> the BlueMarble images cover the whole planet, so, unless you have images 
>> from other multiple geostationary positions (or unless it's not
>
>   I'm a poor man, I only have one geostat satellite ;)

Ah! So you're Thierry rather than the girl in the gif :o(
Well, to state the obvious, you can only get a partial earth coverage with 
the images you've got.

>
>> Mapping the cloud cover image precisely to the projection of the 
>> BlueMarble images is likely to be tricky (if you need to do that).
>
>   You hit the real point here... I'm seeking for that mapping.
>
>   http://foo.buvette.org/trucs/geostatpics.tar.gz (6 Mo)

Ok. Well here's my idea:

At a geostationary distance (37,786km according to Wikipedia) the image 
should be fairly close to a linear projection, so you should be able to use 
the spherical camera trick to get something fairly close to what you want. 
Here's an example:

//camera {spherical location 0 look_at z}
camera {location <-1,2,-2> look_at 0}

sphere {0,1
  pigment {
    image_map {jpeg "nuages.jpeg" once}
    translate -y
    scale <1.61,0.7,1>
    translate -x+y
  }
  finish {ambient 1}
}

The second camera definition may be handy to understand quite what's going 
on. The image is mapped straight through the sphere like the letters passing 
through a stick of rock at the seaside (hope that analogy works for you). 
You can think of it as the light passing back from the satellite in almost 
parallel rays and staining the sphere. The spherical camera looking out from 
the centre of the sphere towards the 'far' side of the sphere draws what it 
sees around the 360 degree surface of the inside of the sphere.

The only bit that's valid for you is the middle half of the top half of the 
image, but I think this should be quite close to the projection used for the 
BlueMarble images. It won't be exact as the light entering the satellite 
doesn't really arrive in parallel rays, but at that sort of distance the 
distortion, although probably noticable, should be fairly small. You may be 
able to improve on the scaling of the original image which I got to by trial 
and error. It would obviously be much easier if the starting image was 
symmetrical and covered a full half of the globe.

Regards,
Chris B.

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