Hi. I would like to use a ray tracing engine to compute the blockage of an
antenna aperture as I rotate the aperture in azimuth and elevation. I was
curious if POV-ray would be a good tool for this application. Details of my
problem are as follows:

I would like to compute the percent of blockage for a circular antenna
aperture located on an airplane. My approach is to launch evenly spaced
rays from the aperture and monitor each ray to determine if it intersects a
surface or escapes to the problem boundary. I am not interested in any type
of multipath (simply blocked or not blocked). I compute the percent
blockage by dividing the total number of rays that intersect a surface by
the total number of rays launched. I need to rotate the aperture in azimuth
and elevation and repeat the process. Additionally, I would like to write
the blockage information to an output file.

I have worked with ray tracing engines before and I know that I can solve
this sort of problem with ray tracing. The problem is that I do not have
access to the engines I worked with in the past. So, I am curious if
POV-ray can solve my problem. I quickly looked through the pov-ray
documentation and it appears that some of the capabilities I need are
present. Before I spend time investigating the capabilities (which I think
is going to take a bit of time) I was curious if anyone could provide me
with a quick answer.

Thank you in advance for any information.

Post a reply to this message

Matt nous apporta ses lumieres en ce 2005-06-20 17:57:
> Hi. I would like to use a ray tracing engine to compute the blockage of an
> antenna aperture as I rotate the aperture in azimuth and elevation. I was
> curious if POV-ray would be a good tool for this application. Details of my
> problem are as follows:
> 
> I would like to compute the percent of blockage for a circular antenna
> aperture located on an airplane. My approach is to launch evenly spaced
> rays from the aperture and monitor each ray to determine if it intersects a
> surface or escapes to the problem boundary. I am not interested in any type
> of multipath (simply blocked or not blocked). I compute the percent
> blockage by dividing the total number of rays that intersect a surface by
> the total number of rays launched. I need to rotate the aperture in azimuth
> and elevation and repeat the process. Additionally, I would like to write
> the blockage information to an output file.
> 
> I have worked with ray tracing engines before and I know that I can solve
> this sort of problem with ray tracing. The problem is that I do not have
> access to the engines I worked with in the past. So, I am curious if
> POV-ray can solve my problem. I quickly looked through the pov-ray
> documentation and it appears that some of the capabilities I need are
> present. Before I spend time investigating the capabilities (which I think
> is going to take a bit of time) I was curious if anyone could provide me
> with a quick answer.
> 
> Thank you in advance for any information.
> 
> 
You can put a light_source at the position of the antena. Then, you can use a sphere,
or watever 
shape you want, with a hole punched in it by using clipped_by. Use a box with the
inverse keyword. 
Then, you need some surface to catch the light. The parts that are lighted are free,
the parts in 
shadow are blocked.
You can orient the aperture with a rotate<x,y,z> command. If the aperture is along the
z axis, you 
only need x and y rotation.

Alain

Post a reply to this message

Hello,

The way I see is...you could:

* Use a "super-fisheye" camera placed at the location of the antenna so it
can see in all directions. This would be a fisheye camera with an angle of
360.
* Use no_image on all of the objects so the camera doesn't see the objects,
just the shadows they create.
* Use a hollow sphere to surround the objects and "catch" the rays.
* Use +q0 in the command line so the pixels will be either white or black.

Since the rays will be evenly distributed along the inner surface of the
hollow sphere, you can calculate the percent blocked by (black
spots)/(bright spots). Heheh...you could use transparency to simulate a
lossy path...but then you would have to use a higher quality setting.

Since the angle is proportional to the radius from the center of the image,
I don't believe you'll have to apply any corrections before you sum up the
bright and dark pixels within the circle. Can anyone confirm this?

I've posted a sample image and code in binaries.images.

Post a reply to this message