David Megginson wrote:
Hi all,Here is a screenshot of KJFK from 3900ft with a 16-bit buffer:http://www.megginson.com/flightsim/jfk-night.png First of all, it looks wonderful. Many of us can remember when the whole world was a desert, and then when we had only forest and grass airport areas with no runways. It's nice to see how far we've come in a short time. Now, with that out of the way, when you look closely, you'll notice that the lights are clearly floating 40 or 50ft above the runways. I wonder if there's any formulation we can come up with that could avoid this. For example, let's say that at a certain distance we need the lights to be 50 ft away from the ground to avoid z-buffer problems. If I'm looking at the airport from 2 miles away at 1,000ft AGL, then my view has slope of about 1:10, so the lights need to be lifted only about 5ft from the ground to get 50ft between them and the ground directly behind (from my current viewing angle). Does this make sense to the math types? All the best, David
First a disclaimer that I am mostly a novice at current graphics processing. I would think that the whole problem can be viewed as one of resolution limitations.
Z buffering problems seem to come from resolution limitation along the line of sight, where the problem is which object to display where one object obscures another. On a low angle approach, the sight line is nearly parallel to the ground surface. However, you now have the limitation of the display's vertical resolution, where the runway surface and a light may still map to the same pixel. This is not a Z axis problem, but X and Y also have limitations.
I would hazard a guess that a proper solution should consider all 3 axes of display limitations, and move the lights just enough to be on a unique pixel, based on the sight line coordinates. Z is only a major problem because so many things tend to be viewed along their surface normals.
--
Bill Earnest wde3@ptd-dot-net Linux Powered Allentown, PA, USA
Computers, like air conditioners, work poorly with Windows open.
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