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EnigmA AMIGA RUN 29 (1998)(G.R. Edizioni)(IT)[!][issue 1998-07 & 08].iso
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spheric_brush_mapping
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1998-05-02
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Date: Mon, 27 Apr 1998 09:50:40 +0100
From: Matthew Petty <MatthewPetty@CDDP.CO.UK>
Subject: [IML] QUEST: brush mapping on a sphere
Halloo
simple one for you pros! I've got a lovely NASA image of the earth's
surface, completely flat, with the North pole stretched across the whole
top edge, and the South the same along the bottom.
I want to map this 1-as colour, and 2- as altitude.
Works fine, except that the poles seem cut off a bit. I've looked at the
Axis for the mapping, and it's dead square on, and the correct size.
What's the problem? Plus, which mapping method should i use, and why.
Discuss.
I know how 'flat' works but the others - dunno.
I've got the moon and jupiter too (but would using gasgiant texture be
more efficient? hmm)
thanks for any help
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Date: Mon, 27 Apr 1998 18:23:26 +0400
From: Charles Blaquiere <blaq@INTERLOG.COM>
Depending on how NASA deformed the collage of snapshots to create the
image you describe, it could be either cylindrical or spherical. (My
guess: spherical) If the poles are cut off, check the texture Y axis; I
believe its size defaults to 1. Change it to 0.001 and see if that
helps.
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Date: Mon, 27 Apr 1998 17:54:04 +0000
From: Andy <andy.k2@UKONLINE.CO.UK>
Organization: Blurred Vision
Hi Mat. In this case, you should be using Cylindrical Mapping. Make sure
that the left and right edges of the Poles on your Bitmap Line up..
Date: Tue, 28 Apr 1998 09:39:39 +0200
From: Torgeir Holm <torgeir@UNION.NO>
Spherical mapping would probably be better.
Grab an onion, place it in the centre of a sheet of newspaper; then pull
the paper up around the onion. Thats how spherical mapping works... the
four corners of you world map would be bunched around the back of the
sphere.
Date: Tue, 28 Apr 1998 09:39:39 +0200
From: Torgeir Holm <torgeir@UNION.NO>
That is NOT how spherical mapping works. It works very similarily to
cylinder mapping, except that it also curves along the z axis, creating
less pixel distortion at the poles. What you're describing is how conform
to sphere works.
You must also make sure your map is perfaectly cropped. You'll get a seem
if theres any spare pixels around it.
Hope that helps.
Note. If the left and right edges of you Planet maps don't line up
properly, just rotate the object so the seem isn't facing the camera.
Date: Tue, 28 Apr 1998 09:39:39 +0200
From: Torgeir Holm <torgeir@UNION.NO>
To get rid of this, open the image in photoshop, and offset it by half it's
width and half it's height. if you can see any visble seems, clone them
away. Offset the image back to the original position, and save.
----------------------------------
Date: Tue, 28 Apr 1998 22:46:15 +0000
From: Andy <andy.k2@UKONLINE.CO.UK>
Hi Torgier,
Jesus, That's two balls ups I've made this week 8)). I've been
mapping my planets wrong all this time. Agh! Heh. I'm sure I read that
bunching paper business about spherical mapping in the Im3 Manual...
I just did a little test, just to be sure ;). I loaded four "earths".
two of each type; spherical and cylindrical. one of each has the Pole
pointing at the camera. you can check for yourself...
http://web.ukonline.co.uk/andy.k2/temp/globe.jpg
It's pretty obvious Torgier is correct, and I'm a plonker 8))
Cheers for putting me rite.
Oh, the spherical mapped globes are on the left.
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