Thursday, June 01, 2006

A subtle change in blastpads

Two, actually...we'll see if these behaviors show up in beta...

This is runway 4L at KBOS, from Google Maps. Note that a taxiway travels behind runway 4L on top of the blastpad.

Now compare how these look in X-plane 840 and X-Plane 850..

In X-Plane 840, the blast pad goes over the taxiways. This is fixed for 850. However you can see that the author may have been expecting this effect - there's a lot of taxiway pavement put down around this junction. The new apt.dat format will alleviate this to some extent by allowing pavement to be shaped in arbitrary polygons, making overlapping no longer necessary.

A more subtle shift: note that the threshhold is not in the same place in 840 and 850. This is because in 840 the blastpad (like most of the runway) is built in square tiles. Since the runway is 150 feet wide, the blastpad is rounded to a mulitple of 150 feet long. In 850, the blast pad is chopped at the exact point, so the threshhold can be where it is supposed to be.

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