> On 29.06.2013 00:09, Christian Froeschlin wrote:

>>
>>> But whatever I try, all I get is an empty black scene... I tried
>>> tweaking the distance of the sun (Earth's center is at the origin),
>>> the illumination direction, correctly applying rotations of mesh2,
>>> camera position and camera direction, but no effect at all.
>>
>> start small ... you seem to assume that the curved mesh itself
>> is correct which is a very big assumption for a first test with
>> such a complicated definition. Make a test scene where you render
>> some spheres at calculated vertex positions for a small subset of
>> coordinates to get an overview of your geometry.
>
> The main problem seems to be that
>
> trace(Earth_Slice, Earth_Pos,
> 2*rd*<sin(radians(-Cam_Long))*cos(radians(Cam_Lat)),
> sin(radians(Cam_Lat)), cos(radians(-Cam_Long))*cos(radians(Cam_Lat))>)
>
> which probes for the mesh, always returns zero... why?
>
> See you in Khyberspace!
>
> Yadgar

you have:
trace{Object, location, direction}

Apparently, you trace from the center of your Earth. Are you sure that 
your direction is actualy toward the slice you are using?
The lenght of the direction vector don't need to be large, you can 
remove the "2*rd*".

Maybe doing a test with the camera placed to see the inside of the slice.
Next, make a cylinder like this:
cylinder{Earth_Pos, 
2*rd*<sin(radians(-Cam_Long))*cos(radians(Cam_Lat)),sin(radians(Cam_Lat)), 
cos(radians(-Cam_Long))*cos(radians(Cam_Lat))>
,1
pigment{rgb<1,0,0>}finish{emission 1}
}

If that cylinder is not directed toward you slice, it mean that your 
math need reworking.

You may try this for your direction:
<sin(radians(Cam_Long)), sin(radians(Cam_Lat)),cos(radians(Cam_Long))>



Alain

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