> Alain<aze### [at] qwertyorg>  wrote:
>
>>
>> The rotation in a rotate statement is not limited to 360 degrees. rotate
>> <1000, -557, 10>  is perfectly legal.
>
> Does this statement mean rotate 1000 (+40 degrees) about x, -197 (+163) degrees
> about y and 10 degrees about z. Or does it define a rotation axis
> <1000,-557,10>? Could you point me to the relevant part of the documentation?
It rotate several times around the X axis, then it rotate around the Y 
axis, then around the Z axis.
Rotations are always done that way.
http://wiki.povray.org/content/Documentation:Tutorial_Section_2.2#Rotate

>
> I think the easiest solution to my particular requirements is to write a C++
> wrapper program to generate the necessary code for the desired rotation in the
> ..pov file.
>
> In my previous post I was trying to ask if one could pass command line arguments
> for the start and stop angle variables, which would be used to correctly
> initialise the corresponding variables at run-time.
>
> eg. povray +Q0 +I<fileName>...<param1=startAngle>  <param2=stopAngle>
Perfectly possible.
You can declare variables on the command line with the following construct:

declare=IDENTIFIER=FLOAT (yes, there are 2 "=" signs)

So, you can have: declare=Param1=12 declare=Param2=79
to set Param1 to 12 and Param2 to 79.

>
>
> But since I am already auomatically generating the .inc and an unix script to
> execute the .pov file(s) in parallel I might as well set the start and stop
> parameters by generating the .pov correctly at run time, i.e. generate a bespoke
> ..pov file based on user input to my program, and then execute the unix script to
> do the raytracing.
If you need several images from various locations, you can use the 
animation feature. Use the internal "clock" variable to controll the 
movement.
Just passing +kffn to the command line will start the animation loop to 
render n successive images.
>
> Is it possible to define an isotropic light source on the (shell) surface of a
> sphere and direct all light rays at the origin: Basically I am only using povray
> to do very crude raycasting to determine the projection of an anatomical
> structure.

No.
You can use other options: (from fastest, cruder, to slowest and nicest)

Using +q0 ignores any light and only use full ambient illumination and 
simple textures/pigments. Any transparency and reflection is ignored. 
Fast and crude.

Use 6 or 8 shadowless lights placed as a cube or octagon. Slightly 
slower. Can use coloured lights to beter show shapes.

Use area_light instead of regular point_light, to illuminate the scene 
from several directions and hide the shadows. Be sure to use adaptive 
sampling, starting with adaptive 0.

Use radiosity with a white background and no actual light. It gives an 
all encompacing illumination. It takes more time to render and may not 
be what you need to do "crude" renders.


>
> Mark
>
>

Alain

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