Re: [Flightgear-devel] KJFK at night
Jim Wilson wrote: That's a little too small to resolve differences at 16bpp. Try the patch below. It decreases the lifting substantially. You will see a slight increase in z-buffer flickering but it isn't bad. Has anyone tried offsetting the lights in the direction of the viewer? While this might look weird for off-axis lights (they would appear to move a little bit as you turned or changed the view), it would (might?) require far less offset to get the same effect. Shouldn't be too difficult to try, anyway. Andy -- Andrew J. RossNextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com Men go crazy in conflagrations. They only get better one by one. - Sting (misquoted) ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] KJFK at night
David Megginson writes: Here is a screenshot of KJFK from 3900ft with a 16-bit buffer: 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? My guess is that the real solution requires taking a different approach http://www.opengl.org/developers/code/sig99/advanced99/notes/node20.html Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] KJFK at night
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 -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] KJFK at night
David Megginson wrote: 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. David, There is one thing to remeber; Approach lights usually are above the field (at least 2 meters). Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] KJFK at night
Erik Hofman writes: 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. David, There is one thing to remeber; Approach lights usually are above the field (at least 2 meters). Thanks. I'm talking about the runway edge and centre lights and taxiway lights, though. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] KJFK at night
David Megginson wrote: 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 Hi all, 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. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] KJFK at night
David Megginson [EMAIL PROTECTED] said: 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? That's a little too small to resolve differences at 16bpp. Try the patch below. It decreases the lifting substantially. You will see a slight increase in z-buffer flickering but it isn't bad. Note that we removed the distance component the other day, the purpose of it was to lift the lights higher when viewed at shallow viewing angles. The distance component is critical for the street lights that can be very long distances away. But with the distances we're working with here it really doesn't do all that much. The factor used in this patch is about as shallow a lift as can be used when looking straight down at the airport. At 24bpp there's no effect from incorporating a distance component. The choice is to reintroduce a distance component...one that works (and only for 16bpp), or alter the factor used in the patch below to strike an acceptable balance between different viewing angles when in 16bpp mode. Best, Jim Index: src/Scenery/tileentry.cxx === RCS file: /var/cvs/FlightGear-0.9/FlightGear/src/Scenery/tileentry.cxx,v retrieving revision 1.13 diff -r1.13 tileentry.cxx 914c914 sgScaleVec3( lift_vec, 0.0 + agl / 20.0 ); --- sgScaleVec3( lift_vec, 0.0 + agl / 150.0 ); 957c957 sgScaleVec3( lift_vec, 0.0 + agl / 20.0 ); --- sgScaleVec3( lift_vec, 0.0 + agl / 150.0 ); ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] KJFK at night
Jim Wilson writes: That's a little too small to resolve differences at 16bpp. Try the patch below. It decreases the lifting substantially. You will see a slight increase in z-buffer flickering but it isn't bad. Note that we removed the distance component the other day, the purpose of it was to lift the lights higher when viewed at shallow viewing angles. Shouldn't the lights be lifted less at shallow viewing angles? The extreme case is sitting on a horizontal runway looking directly between the lights and the ground. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
