On July 25, 2005 06:42 am, Vivian Meazza wrote: > Radar Echoing Area is (REA) and is also known as the Radar Cross Section > (RCS). It's not quite the same thing as the radar visibility range. > > RCS is a property of the target, and varies with the target aspect w.r.t. > the radar, and also the radar frequency. > > Radar visibility range is a function of the RCS and the power density of > the radar at the target. > > Depending on the level of realism you want for radar, we either need a > crude visibility range as a property of the target, or the RCS (probably an > estimate) and have the radar work out if the target is visible, taking into > account the RCS and the radar horizon. > > Vivian The RCS idea also occured to me a while ago. In fact, I have actually given it some thought as to how such effect would work in FlightGear.
The first idea involves estimating the radar reflection of aircrafts in real time. A camera with an aspect ratio of 0.1 will act as the radar and cycle its view through all the aircrafts in the vicinity at certain intervals. The camera will render what it sees off screen, without any light other than a spot light pointing in the same direction as the camera, without fog, without clouds, without billboard objects, with the sky as black and everything else according to their specular reflectiveness. The renderings will then be analyzed later, with the "visibility" of each plane corresponds to the average brightness of their rendering. This method will be slow, but it will give some nice effects. The most notable are probably terrain obstructions and interferences. The second idea involves mapping out the RCS values of the planes at different angles, and storing the results in 360x360 pixels, mono-color bitmaps. Then it is simply a matter of doing a look up in FlightGear to find out the RCS of a plane at any given moment, multiplying the value by the power of the radar, and dividing the result by the square of the distance between the plane and the radar This will be much faster than the first method, although it won't give such effects as terrian obstructions and interferences. Ampere _______________________________________________ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
