Hi All,
I am trying to simulate images of GEO satellites taken from a ground-based
telescope, represented by the camera. I know that many GEO satellites creates
glint when their solar panels reflect the light towards the observer. I have
already created the geometry and calculated their position.

The issue I am experiencing now is the following:

- I used a small FOV (angle 0.35) to simulate the telescope, and the objects in
the scene (Sun and Satellite) have been rendered 1000 times closer to it in
order to make them visible. However, the solar panels seem not to be shiny
enough to generate a quasi-instantaneous glint as I would expect.

These are the finish properties given to the solar panels, together with a
Polished_Chrome texture:

Ambient: 0.0001
Diffuse": 0.0001
Specular: 1.0
Roughness": 0.00001
Reflection": 1.0
Brilliance": 100.0

Does anyone know how can I make them shinier? Is it a problem related with the
material or is it due to the very low FOV?

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hi,

"Gabriele " <nomail@nomail> wrote:
> ...
> These are the finish properties given to the solar panels, ...
> Does anyone know how can I make them shinier? Is it a problem related with the
> material or is it due to the very low FOV?

cannot answer either question, but I'd be inclined to start with a "perfect"
mirror, then explore from there.  have you looked at/used 'finish.inc' yet?


regards, jr.

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Le 2020-11-20 à 07:24, Gabriele a écrit :
> Hi All,
> I am trying to simulate images of GEO satellites taken from a ground-based
> telescope, represented by the camera. I know that many GEO satellites creates
> glint when their solar panels reflect the light towards the observer. I have
> already created the geometry and calculated their position.
> 
> The issue I am experiencing now is the following:
> 
> - I used a small FOV (angle 0.35) to simulate the telescope, and the objects in
> the scene (Sun and Satellite) have been rendered 1000 times closer to it in
> order to make them visible. However, the solar panels seem not to be shiny
> enough to generate a quasi-instantaneous glint as I would expect.
> 
> These are the finish properties given to the solar panels, together with a
> Polished_Chrome texture:
> 
> Ambient: 0.0001
> Diffuse": 0.0001
> Specular: 1.0
> Roughness": 0.00001
> Reflection": 1.0
> Brilliance": 100.0
> 
> Does anyone know how can I make them shinier? Is it a problem related with the
> material or is it due to the very low FOV?
> 
> 
> 

You can set your ambient to zero.
Increase the specular, maybe in the 3..4 range, maybe even more.
Set your roughness to something slightly larger, like 0.001 to 0.0001.
You probably don't need to play with the brilliance at all.

Your problem may be that the panel covers less than a full pixel. 
Solution : Make them larger or render at a larger resolution so that 
they can fill a pixel or slightly more.

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On 2020-11-20 8:24 AM (-4), Gabriele wrote:
> 
> These are the finish properties given to the solar panels, together with a
> Polished_Chrome texture:
> 
> Ambient: 0.0001
> Diffuse": 0.0001
> Specular: 1.0
> Roughness": 0.00001
> Reflection": 1.0
> Brilliance": 100.0

The smaller your roughness value, the less specular highlight you get. 
To counteract this, use specular albedo.  I suspect this is the main 
problem.  You might also need to increase roughness to, say, 0.0001.

Reflection + ambient + diffuse should never be more than 1.0.  However, 
your values ambient and diffuse values are so small it should not make a 
difference.

Ambient should normally be much smaller than diffuse.  And since in 
outer space, the only significant source of ambient light comes from 
Earth, at the geosynchronous distance ambient should be even tinier, the 
exact proportion depending on how much of the sunlit portion of Earth is 
visible from the satellite.  But again, your values are too small to 
make a difference.

Brilliance is irrelevant with such a small diffuse value.  But since you 
are looking for a specular effect rather than diffuse reflection, 
brilliance is the wrong knob to tweak.  You should leave brilliance at 1.0.

Since your settings override all the Polished_Chrome values except the 
Phong settings (which only complicate the highlight situation), you 
might as well drop it and just use pigment { rgb 0 }.  Or rgb 
<whatever-is-silicon's-albedo>.

Your settings are also physically unrealistic for a solar panel, 
although this does not relate directly to your problem.  Unless you are 
using Fresnel reflection, the reflection value should not be 1.0, 
because if you reflect all of the light, none of it gets to power the 
satellite!  But for glass, you should be using 'reflection { 1.0 fresnel 
} conserve energy' anyway; this allows a realistic amount of energy to 
be transmitted to the solar cells.

Unfortunately, POV-Ray 3.7 does not implement the Fresnel effect for 
highlights.  To get a good average highlight, use 'specular albedo 
0.05'; but at shallow angles, for example, looking towards the west 
after sunset, specular albedo should be closer to 1.0.  POV-Ray 3.8 can 
take care of all these complications: use 'fresnel 1.0 reflection { 1.0 
} conserve_energy specular albedo 1.0', making sure that the fresnel 
keyword is *outside* the reflection block.

> Does anyone know how can I make them shinier? Is it a problem related with the
> material or is it due to the very low FOV?

I have had problems with low FOVs, but they have affected only geometry, 
not material properties.

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Cousin Ricky <ric### [at] yahoocom> wrote:
>
>   But for glass, you should be using 'reflection { 1.0 fresnel
> } conserve energy' anyway

That should be conserve_energy with an underscore.

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