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hpolloni

skydome ugly texture glitch

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im making a skydome algorithm generating the sky texture blending a cloud alpha texture generated with perlin noise and a gradient. The effect is great, but the problem i have is that in the pole of the dome ocurr this glitch: clicky i thinking that this ocurr maybe because the right and left part of the texture doesn't match. Also i try just zeroing the upper part of the clouds alpha , so only the gradient will show on the pole, but it look very ugly. Another solution will be using fog to cover the pole, but i also didn't like the effect. Maybe i over thinking this and putting to much effort in an eye-candy that most players don't appreciate. Any answer will be greatly appreciated. PS: Sorry for my lame english.

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I don't have a precise answer for you, but from looking at that screenshot it looks the same as when I've made some really crappy geometry in 3DSMax using rubbish texture mapping on a sphere.

Maybe you'd get a better result if you used a more "sphere friendly" texture coordinate projection system. I know they exist, here's a couple of resources I came across when having a look around:
Spherical Textures
Google search for 'Spherical Texture Mapping'
Some of the links appear to be similar to some of the projections used to draw 2D/flat pictures of the atlas..

hth
Jack

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Quote:
i thinking that this ocurr maybe because the right and left part of the texture doesn't match.

no, it occurs cause of trying to map a 2d square texture onto a sphere/hemisphere, which is impposible (get a piece of paper wrap it around a tennisball see that a lot of the paper is bunched up in one spot, thats sorta whats happenign with your app)
u will need to choose different texture coordinates, perhaps a 2d plane projected down from above, this will lead to stretching at the bottom of the skydome, thus lower the skydome a bit and it should be hardly noticable

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Quote:
Original post by zedzeek
no, it occurs cause of trying to map a 2d square texture onto a sphere/hemisphere, which is impposible (get a piece of paper wrap it around a tennisball see that a lot of the paper is bunched up in one spot, thats sorta whats happenign with your app)

I wouldn't go so far as saying impossible - there are various projections so you can get a 2D representation to appear correctly on a sphere (see my links). However, it does require a non-trivial solution - the basic mapping, as we've both pointed out just doesn't cut it in this situation [smile].

hth
Jack

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