Thanks Bill for your reply and your explanations.

I've been able to do some modifications which turn the horizon tint into a more realistic feature such as dawn or dusk, at least in my opinion !

After some solutions, I adopted the ones consisting in the following modifications:
all "7f0000" have been replaced by "5f0000"
all "3f0000" have been replaced by "2f0000"
all "200000" have been replacedby "000000"

With these numbers, the horizon band fade regulary into the sky, up to 8 degrees above the horizon line, where it can no longer be seen.

Thanks again.

Bertrand

----- Original Message -----
From: Bill J Gray
To: guide-user@yahoogroups.com
Sent: Tuesday, July 05, 2005 10:08 PM
Subject: Re: [guide-user] Object.dat file


Hi Bertrand,

Aha! I should have realized it wouldn't be anything quite that easy...

(For those wondering what Bertrand is talking about: see

http://www.projectpluto.com/update8b.htm#horizon

The horizon file provided there includes a blue tint near the horizon,
plus some new objects.)

You're right; changing the color of these objects is not so easy.
The only way to do it would be to edit 'objects.dat', then change the
colors given for the triangles that make up the horizon. For each
triangle, three colors are given (one for each corner of the triangle);
in between, the colors are interpolated. For example, consider the
first few lines of the revised 'objects.dat':

; A description of this file appears at its end.
; A 'segment' of the blue horizon tilt, covering a ten-degree segment: */
o blue_segment
r -5 0 7.5 8
t 3 7
-5 0 7f0000
-2.5 3 3f0000
-2.5 0 7f0000

'7f0000' and '3f0000' are RGB color values. The first corresponds to a
half-intensity blue; the second, to a quarter-intensity blue.

You could adjust these to be fainter colors, or shades of red, or
something else.

I didn't work very hard on making the horizon band adjustable, because
I felt that the 'realistic sky' option made it almost obsolete.

-- Bill




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