Charon/isophote xtrol/perspective views of earth

Bill J Gray Jun 22, 2002

Hi folks,

Catching up on some previous posts here:

Matt Dawson asked about some problems in running Charon with Guide 8.
The problem here is that Charon hasn't caught up (yet) with the new
system for installing Guide to the hard drive. Until I fix this,
you've two choices. You can run Charon with the Guide CD in the CD
drive, or you can install Guide to the hard drive the "old-fashioned"
way as was done in Guide 7 (copying everything over from CD to hard
drive, then modifying STARTUP.MAR to point to a different path; see

http://www.projectpluto.com/harddriv.htm

for details.)

About "vanishing"/hard-to-control isophotes: Now that you mention
it, I'm kinda surprised I'd not gotten comments about this before.
Quite a bit of the control of isophotes depends on being able to
right-click on one. If you can't do that, you're almost completely
out of luck. I'll see if I can come up with a way around that...

Robert Orso wrote:

"...Lately I tried to add a 'country border' overlay to a satellite
image and thought Guide would perfectly fit to produce this..."

Unfortunately, as you found, it doesn't do a very good job of
this. The problem is that, when I added Guide's code to show
bitmapped planets, I figured that such views would always be
essentially from infinity. Perspective effects are completely ignored.

Long after the fact, I came up with a way to show bitmapped
planets that would allow for perspective rendering, plus "shape"
effects (so irregular objects such as Phobos, Deimos, and a few
asteroids and other planetary satellites that have shape data), _and_
would be _much_ faster than the current system. However, ripping out
the existing system and replacing it would be a huge job, and I've
been putting it off.

What you can do is this. First, set your "viewpoint" to be from
the satellite. (For details on how to do that, see

http://www.projectpluto.com/useless.htm#odd_viewpoints

Looking back at the earth, right-click on it and select "Display...
Options" to get the dialog box where you can select which bitmap is
used and whether features are shown. Make sure that "features" are
turned on.

The fact that the country/coastline features are shown with correct
perspective, and the bitmap ones are not, will be very apparent.

In the "geographic"/eclipse mode, by the way, the best you can do
is to set the orthographic projection. But this, too, gives you a "view
from infinity". There is no "view from altitude X" projection.

-- Bill