Am 01.09.2010 11:04, schrieb bobsta:

> i) is it better to rotate the camera about the direction vector, or apply the
> inverse camera matrix to the structure (to rotate and translate it) and keep the
> camera fixed (thereby generating the same image)

As you are /thinking/ about the animation in terms of a camera rotation, 
that's what you should go for. It will also prevent you from having to 
rotate the light source(s), sky sphere, and whatever else you have in 
the scene.

> ii) how can I automate the orbit? Do I need to generate a .pov file for a single
> camera position. Or can I read in one file containing the mesh2 object and then
> pass a number of simple "camera" files to povray containing the necessary camera
> setup. Or should I simply define all camera positions in the .pov file and allow
> povray to serially raytrace each camera (60<  number of cameras<= 180)

POV-Ray has some built-in features to help creating animations. By 
specifying the command line parameter (e.g.) "+KFF100" (or INI-file 
parameter "Final_Frame=100") you tell POV-Ray to render the scene file 
100 times, varying a variable named "frame_number" from 1 to 100 and 
appending the same number to the output file name. There's also a 
"clock" variable, varying from 0.0 to 1.0 by default.

In your scene file, you would then use just a single camera, but compute 
its position from "frame_number" or "clock", e.g.

   camera {
     rotate y*360*clock
   }

which would have the camera position rotate around the Y axis in steps 
of 3.6 degrees per frame (presuming Final_Frame=100).

If you absolutely /need/ to go through the pain of manually defining the 
individual camera positions, you'd typically use a "#switch" construct.

See also sections 2.3.8 "Making Animations" and 3.2.1.3.6 "Built-in 
Variables" of the documentation


> iii) is it possible to write a pbm file directly with povray since I am really
> only interested in whether the image pixel is inside (1) or outside the mesh (0)
> As far as I can tell povray outputs .png .tga or .ppm. Since speed is critical I
> want to avoid having to convert the images into pbm files (which are used for
> further processing)

No - POV-Ray being a raytracing software, file formats with a bit depth 
of 1 are a pretty seldom asked-for feature. The current v3.7 beta does 
support .pgm as well, but that's as close as you'll get.


> iv) is there a way to batch run the raytracing of multiple structures either in
> series or preferably in parallel on different CPUs?

I know of two "out-of-the-box" ways of rendering a set of images in a batch:

(A) Use an external script, such as a Unix shell script.

(B) Use the built-in animation mechanism. You can not only #switch 
between different cameras or object, but even whole scenes if you so wish,


As for making use of multiple CPUs or CPU cores, there are also 
different approaches:

(A) Simply run multiple instances of POV-Ray in parallel, each rendering 
a different frame or scene of your batch. (For best performance, make 
sure not to run more instances than you have (virtual) CPU cores.)

(B) Go for the POV-Ray 3.7 beta, which is pretty stable to use by now, 
and does symmetric multiprocessing out-of-the-box, taking all cores it 
can get by default.

For your particular situation, solution (A) may be better suited though, 
as during scene file parsing even the POV-Ray beta uses only a single 
core, and from your description I guess your scenes may take more time 
to parse than to actually render.

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