Re: [Flightgear-devel] Geo formulae

2003-11-13 Thread Paul Surgeon
On Thursday, 13 November 2003 00:36, Norman Vine wrote: One way todo this is to always use the same size texture so as to be able to use glTexSubImage2D() to control the level of detail and mipmaping ourselves. Easiest todo this if the scenery is laid out so when you go to a lower level

RE: [Flightgear-devel] Geo formulae

2003-11-13 Thread Norman Vine
Paul Surgeon writes: On Thursday, 13 November 2003 00:36, Norman Vine wrote: One way todo this is to always use the same size texture so as to be able to use glTexSubImage2D() to control the level of detail and mipmaping ourselves. Easiest todo this if the scenery is laid out so when

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Curtis L. Olson
Paul Surgeon writes: I'm not sure how to compute this : If I lay out a runway in an unprojected view (flat) and then convert it into FG format (projected) how much will the runway be distorted at latitudes of 60 degrees? i.e How much distortion could I expect over a distance of 2-3 km at

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Paul Surgeon
On Wednesday, 12 November 2003 21:22, Curtis L. Olson wrote: FlightGear goes to great lengths to map the airports correctly on the curved surface of the earth at any latitude. If I recall, the procedure converts each runway corner to an angle and distance from the center point, then it feeds

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Curtis L. Olson
Paul Surgeon writes: Holy cow! About 25% of that passed right over my head. :) Good, you are doing better than me then. :-) When you said that FlightGear goes to great lengths to map airports correctly I assume you mean that the TerraGear scenery building process does that? Yes. Am I

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Paul Surgeon
On Wednesday, 12 November 2003 22:28, Curtis L. Olson wrote: Good, you are doing better than me then. :-) What? I thought you wrote this stuff. The FlightGear world preserves the shape of the wgs-84 ellipsoid, so if you draw things far enough out, you will see the actual curvature of the

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread David Luff
On 11/12/03 at 10:16 PM Paul Surgeon wrote: On Wednesday, 12 November 2003 21:22, Curtis L. Olson wrote: FlightGear goes to great lengths to map the airports correctly on the curved surface of the earth at any latitude. If I recall, the procedure converts each runway corner to an angle and

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Curtis L. Olson
Paul Surgeon writes: What? I thought you wrote this stuff. Yes, I wrote a lot of it, but I'm not claiming perfect memory. :-) Yes you mean it actually wraps the data around an ellipsoid not on a flat plane like some simulators. It's a very nice accurate system although a bit complex to

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Paul Surgeon
On Wednesday, 12 November 2003 23:04, David Luff wrote: Hi Paul, I'm not entirely sure what you're trying to do, or where in the world you're trying to do it to, but from some of your previous comments it sounds like you might be trying to overlay satelite or aerial photo images onto the

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Curtis L. Olson
Paul Surgeon writes: If anyone who understands this is still reading, am I right in thinking that FG loads up all of the possible scenery textures mentioned in the materials file at startup and keeps them until shutdown I get a strong feeling that this is the way it works (haven't stuck

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread Norman Vine
Curtis L. Olson writes: Like you say, to do this well, we would need some way to efficiently page texture data in and out. We'd also want to be able to load lowres mipmaps for distant stuff and hold off loading the full resolution version of the textures until they are close enough to

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread David Luff
On 11/12/03 at 5:36 PM Norman Vine wrote: Curtis L. Olson writes: Like you say, to do this well, we would need some way to efficiently page texture data in and out. We'd also want to be able to load lowres mipmaps for distant stuff and hold off loading the full resolution version of the

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread Curtis L. Olson
David Luff writes: One way todo this is to always use the same size texture so as to be able to use glTexSubImage2D() to control the level of detail and mipmaping ourselves. Easiest todo this if the scenery is laid out so when you go to a lower level texture it covers 4 times the area and

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Andy Ross
David Luff wrote: I'm not entirely clear on this - are mipmaps pre-built and available on disk for FG to load, or are they built from the main texture at runtime? The latter. I believe in our case it's done by plib, but there's a standard gluBuild2DMipmaps() routine in OpenGL too. The time

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread Norman Vine
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of David Luff Sent: Wednesday, November 12, 2003 5:39 PM To: FlightGear developers discussions Subject: RE: [Flightgear-devel] Geo formulae On 11/12/03 at 5:36 PM Norman Vine wrote: Curtis L. Olson

Re: [Flightgear-devel] Geo formulae

2003-11-12 Thread Andy Ross
Curtis L. Olson wrote: This can get to be a really complicated subject if we let it. But, as it works now, a single full res texture is stored on the disk. It is loaded at run time, and the mipmaps are generated using a simple 2x2 - 1x1 averaging scheme. (I think this is called a box

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread Norman Vine
Curtis L. Olson writes: But, we could always just do the internal mipmap generation as we need it. That would mean keeping a copy of the full res texture in main ram though. Not necessarily. i.e. glTexSubImage2D() actually replaces the texture content so as to have it cover 4 times the

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread Norman Vine
Andy Ross writes: David Luff wrote: I'm not entirely clear on this - are mipmaps pre-built and available on disk for FG to load, or are they built from the main texture at runtime? The latter. I believe in our case it's done by plib, but there's a standard gluBuild2DMipmaps() routine

RE: [Flightgear-devel] Geo formulae

2003-11-12 Thread David Luff
On 11/12/03 at 4:45 PM Curtis L. Olson wrote: David Luff writes: I'm not entirely clear on this - are mipmaps pre-built and available on disk for FG to load, or are they built from the main texture at runtime? This can get to be a really complicated subject if we let it. ...snip lots! Thanks