Celestia Forums

Ok. Right now, I don't know of a way to implement looping seasonal texture changes in Celestia, but having recently figured out a good technique for making ice caps (derived from Vliet's helpful tips found here), I'm thinking of making 12 texture sets for an alternate Earth that has a high obliquity, with everything else (EquatorAscendingNode, RotationPeriod, etc) being exactly the same.

Did you think I made the Obliquity exactly -90 when you read that?

No, I didn't. I like a fair bit of creativity.

The Obliquity value I use in Celestia is -79.91963239. Okay, maybe a bit too close to 80.

Anyways, I said 12 texture sets. That means one set for each of the 12 months in our year.

Of course, what I don't know is, which months would have their appropriate average ice cap latitude reach? However, I DO know that seasonal lag needs to be taken into account. I know that seasonal climates lags about a month behind their associated Equinoxes and Solstices. Would it still be a month's lag with my higher obliquity?

And yes, it's probably a bit of a stretch, but I'm keeping the Earth otherwise habitable by our current standards and occupied by our dear old humanity.

PlutonianEmpire wrote:Ok. Right now, I don't know of a way to implement looping seasonal texture changes in Celestia, ...

See also topic http://www.shatters.net/forum/viewtopic.php?f=4&t=15909 about some possibilities...

Marco Klunder wrote:

PlutonianEmpire wrote:Ok. Right now, I don't know of a way to implement looping seasonal texture changes in Celestia, ...

See also topic http://www.shatters.net/forum/viewtopic.php?f=4&t=15909 about some possibilities...

Cool, I'll check it out. Thanks.

When writing the OP, I forgot to clarify that what I'm looking for in regards to the actual textures, is how close the ice-caps grow from the poles towards to, and away from, the equator, month by month, given the data I provided in the OP AND with a number of constraints being the following: the ice caps are deliberately locked to the poles, meaning NO equatorial ice belt, and NO global snowballing, and that the winds do NOT rush away from the hotter pole at debilitating speeds.

Basically, a typical "soft sci-fi"-ish version of the high obliquity scenario, if you will. Of course, at solstices, the sunlit side would still be hot, and the sunless side would still be frozen, with most, if not all, of the victim hemisphere covered in ice. Basically, the status quo, but more extreme, and of course, Earth remaining habitable and inhabited by everyone we know and love.

So yeah, this is what I meant by "average ice cap extension" in the OP.

Anyone wanna help? I'm just looking for latitude numbers, indicating the ice cap is this far south/north, etc.

Maybe you must enstabilish the min. latitude north for the nothern polar cap at winter solstice (that is, you do not wish that the ice cap does moves too much toward the equator at such season, right?); then the min. latitude north at summer solstice (that is, you do not wish that the ice cap does NOT move yet toward the equator at such season, right?. Then do divide such range by six. Finally, do repeat the same for the southern emisphere.

EDIT LATER:
For the textures' composition, the max. polar cap coverage for the winter nothern emisphere the min. polar cap coverage for the summer southern emisphere, and so on for the remains months. Hope I've been clear.

Fenerit wrote:Maybe you must enstabilish the min. latitude north for the nothern polar cap at winter solstice (that is, you do not wish that the ice cap does moves too much toward the equator at such season, right?); then the min. latitude north at summer solstice (that is, you do not wish that the ice cap does NOT move yet toward the equator at such season, right?. Then do divide such range by six. Finally, do repeat the same for the southern emisphere.

EDIT LATER:
For the textures' composition, the max. polar cap coverage for the winter nothern emisphere the min. polar cap coverage for the summer southern emisphere, and so on for the remains months. Hope I've been clear.

Yeah, makes sense actually. I was also thinking that at solstices (or shortly after, due to seasonal lag, which I think is about one month), the seasonal ice caps from one pole would actually cross the equator and into the opposing hemisphere, since the obliquity is close to 80° after all, and absolutely no ice at said hemisphere's pole -- until its own winter rolls around, that is.

Would the formula still work in that scenario?

So for example: June 21'st, Northern Summer Solstice, the North Pole would have no ice at all. The vast majority of the Southern Hemisphere is covered in seasonal snow and ice, and a significant portion of the Southern Hemisphere's Ice Cap extends as far as 5° to 10° N. Due to seasonal lag, the ice caps will make their farthest reaches at most 15° to 20° N one month later on July 21'st before retreating.

Dec 21st to Jan 21'st, same thing, but reversed; No ice or snow at the South Pole, Northern ice and snow covers most, if not all, the northern hemisphere, and again reaching across the equator 5, 10, 15, 20° before retreating after January.

BUT. During the Equinoxes and transitions between the solstices, the ice caps change normally as they would with Earth's Real life Obliquity of 23°; meaning the ice cap edges slowly move towards their respective poles, so no ice whatsoever at the equator.

So, when I said no Ice belt at the equator in the OP, I screwed up, and I apologize for that; I should have said no permanent ice at the equator, as the ice caps are still centered at the poles as always, just they have the ability to expand enough to across the equator, while the sunlit pole has no ice/snow.

It crosses the equator, 'cuz we here in Minnesota know what happens when the sun gets low.

Basically, I'm wondering about the transitional periods between Solstices. Another screw up of mine in that I forgot to mention it.

So, I apologize if I'm being dense, or annoying, or something.

For reference, the Earth at solstice, with my tilt built in. Obliquity value set to -79.91963239



(No, no Mayan hocus pocus here; I've had the SSC for this for about two years now, for something unrelated.)

Mmmmm... I wonder about how cold seasons can do liquefying the equatorial ice when neither the hottest ones are able to do it. If the northern emisphere has ice at equator when it is at proper summer' solstice because the southern winter and viceversa, I do not know how the ice will turn into water at equinoxes, since this latter is a season more cold for both so that the frostening would be summed up (as you can see on Earth, where at spring/summer's tropics there are rainy days; that rain maybe should be permanent snow for such tilted axes).
Anyhow, to reply, and premise that I do not know how the program with which you develop the polar caps works, whether in "additive" or "subtractive" form, each piece-per-month that would be subtracted from equator should be so (degrees are ice cap coverage):

180° - (90°S + x°N) is the northern polar cap at north summer solstice;
180° - (90°N + x°S) is the southern polar cap at south summer solstice;

then:

180° - [180° - (90°S + x°N) + 180° - (90°N + x°S)] / 6

will get the "empty pieces" of the ice's recession for both the emispheres rispectively, within the solstice-solstice interval (max. summed up recession at equinoxes); then fill/no fill up the pieces with ice accordingly to the months (I do not know how you do figure out the painting work).

Does it make sense?

Sorry, my mistake: read

180° - (90°S + x°N) is the southern polar cap at north summer solstice;
180° - (90°N + x°S) is the northern polar cap at south summer solstice;

the rest is the same.

Fenerit wrote:Mmmmm... I wonder about how cold seasons can do liquefying the equatorial ice when neither the hottest ones are able to do it. If the northern emisphere has ice at equator when it is at proper summer' solstice because the southern winter and viceversa, I do not know how the ice will turn into water at equinoxes, since this latter is a season more cold for both so that the frostening would be summed up (as you can see on Earth, where at spring/summer's tropics there are rainy days; that rain maybe should be permanent snow for such tilted axes).
Anyhow, to reply, and premise that I do not know how the program with which you develop the polar caps works, whether in "additive" or "subtractive" form, each piece-per-month that would be subtracted from equator should be so (degrees are ice cap coverage):

180° - (90°S + x°N) is the northern polar cap at north summer solstice;
180° - (90°N + x°S) is the southern polar cap at south summer solstice;

then:

180° - [180° - (90°S + x°N) + 180° - (90°N + x°S)] / 6

will get the "empty pieces" of the ice's recession for both the emispheres rispectively, within the solstice-solstice interval (max. summed up recession at equinoxes); then fill/no fill up the pieces with ice accordingly to the months (I do not know how you do figure out the painting work).

Does it make sense?

Fenerit wrote:Sorry, my mistake: read

180° - (90°S + x°N) is the southern polar cap at north summer solstice;
180° - (90°N + x°S) is the northern polar cap at south summer solstice;

the rest is the same.

Yeah, my "opposite" latitude of choice for solstice ice cap stretch is around 20° past the equator, so, taking the first formula (south ice cap at north summer), "180° - (90°S + x°N)", I put it into my calculator "180 - (90 + 20)", and got 70. Did I do it right so far? If so, what does it represent and what do I do with the 70?

I'm using the same latitude reach for the other formula too (20°), so it is again "180 - (90 + 20)", with 70 as the outcome.

Putting the whole third formula into the calculator with my specified numbers gave me 156.6666.... (repeating). Is this correct?

(As for drawing the ice caps, I use some of the tricks provided by vliet, combined with my own personal methods. )

PlutonianEmpire wrote:Putting the whole third formula into the calculator with my specified numbers gave me 156.6666.... (repeating). Is this correct?

Ah, well... The division's sign...

The formula should give:
(180° - 140°) / 6 = 40°/6 = 6.6666...° each piece. 70° degree is the part of the emisphere(s) which are not covered by ice at solstice.

Fenerit wrote:

PlutonianEmpire wrote:Putting the whole third formula into the calculator with my specified numbers gave me 156.6666.... (repeating). Is this correct?

Ah, well... The division's sign...

The formula should give:
(180° - 140°) / 6 = 40°/6 = 6.6666...° each piece. 70° degree is the part of the emisphere(s) which are not covered by ice at solstice.

Ah, that made it easier. I figured out there needed to be an additional set of parentheses, like this:

(180° - (180° - (90°S + x°N) + 180° - (90°N + x°S))) /6

Yes. I forgot to enclose all within parentheses. Sorry but I'm out of my holidays and my synapses are disconnected.

Fenerit wrote:Yes. I forgot to enclose all within parentheses. Sorry but I'm out of my holidays and my synapses are disconnected.

No worries.

Note that to avoid some discoursive contraddictions about the formulas:

180° - (90°S + x°N) is the southern polar cap at north summer solstice;
180° - (90°N + x°S) is the northern polar cap at south summer solstice;

and the "70°" like the "free ice emispheres", when was saying that the degrees were the ice caps coverage, the summing of degree south with degree north is not "additive" and within the parentheses above 90°S + 20°N is him 70°; the 180° - 70° = 110° of ice coverage for "the southern polar cap at north summer solstice" and the same for the remain emisphere. The total of course does give (110°+110°) - 180° = 40°.

Fenerit wrote:Note that to avoid some discoursive contraddictions about the formulas:

180° - (90°S + x°N) is the southern polar cap at north summer solstice;
180° - (90°N + x°S) is the northern polar cap at south summer solstice;

and the "70°" like the "free ice emispheres", when was saying that the degrees were the ice caps coverage, the summing of degree south with degree north is not "additive" and within the parentheses above 90°S + 20°N is him 70°; the 180° - 70° = 110° of ice coverage for "the southern polar cap at north summer solstice" and the same for the remain emisphere.

Ah, ok. As for the 6.666.... provided by the full formula, what does that represent?

I think the simple 6 the formula is divided by at the end is the number of the month in the year, right?

PlutonianEmpire wrote:I think the simple 6 the formula is divided by at the end is the number of the month in the year, right?

Is the simmetric interval solstice-solstice of equatorial ice advancement/regression for both emispheres. To say, at north summer solstice the ice cap is free while the ice border is at 20° north (110° south) and does recede of 6.6..° per month. At the autumnal equinox it will be receded of 20°(6.6..°x3) meanwhile forming 55° ([70°/2]+20°) of ice at pole. After the next three months, the north polar cap will be at 110° (55°x2, or 20°S) and the south emisphere will be free of ice cap. Then the things are simmetric.

Fenerit wrote:

PlutonianEmpire wrote:I think the simple 6 the formula is divided by at the end is the number of the month in the year, right?

Is the simmetric interval solstice-solstice of equatorial ice advancement/regression for both emispheres. To say, at north summer solstice the ice cap is free while the ice border is at 20° north (110° south) and does recede of 6.6..° per month. At the autumnal equinox it will be receded of 20°(6.6..°x3) meanwhile forming 55° ([70°/2]+20°) of ice at pole. After the next three months, the north polar cap will be at 110° (55°x2, or 20°S) and the south emisphere will be free of ice cap. Then the things are simmetric.

Do you think you can explain this a bit more in-depth?

I'm trying to figure out how those pieces of the puzzle fit together.

"At the autumnal equinox it will be receded of 20°(6.6..°x3)" makes me think it receded by 20° and giving it a 90° (equatorial) extension, although "meanwhile forming 55° ([70°/2]+20°) of ice at pole" gives me the impression of the cap going down to 35°N at north autumnal equinox.

PlutonianEmpire wrote:

Fenerit wrote:

PlutonianEmpire wrote:I think the simple 6 the formula is divided by at the end is the number of the month in the year, right?

Is the simmetric interval solstice-solstice of equatorial ice advancement/regression for both emispheres. To say, at north summer solstice the ice cap is free while the ice border is at 20° north (110° south) and does recede of 6.6..° per month. At the autumnal equinox it will be receded of 20°(6.6..°x3) meanwhile forming 55° ([70°/2]+20°) of ice at pole. After the next three months, the north polar cap will be at 110° (55°x2, or 20°S) and the south emisphere will be free of ice cap. Then the things are simmetric.

Do you think you can explain this a bit more in-depth?

I'm trying to figure out how those pieces of the puzzle fit together.

"At the autumnal equinox it will be receded of 20°(6.6..°x3)" makes me think it receded by 20° and giving it a 90° (equatorial) extension, although "meanwhile forming 55° ([70°/2]+20°) of ice at pole" gives me the impression of the cap going down to either 35°N at north autumnal equinox.

Eh, eh... I will reply when you should explain why 6.6..°x 12 months doesn't give 70° but 80°.

Fenerit wrote:Eh, eh... I will reply when you should explain why 6.6..°x 12 months doesn't give 70° but 80°.

Ummm... Because I got 80 on my Windows Calculator?

I got that 70 from this post, the origin sentence highlighted in bold:

PlutonianEmpire wrote:

Fenerit wrote:Mmmmm... I wonder about how cold seasons can do liquefying the equatorial ice when neither the hottest ones are able to do it. If the northern emisphere has ice at equator when it is at proper summer' solstice because the southern winter and viceversa, I do not know how the ice will turn into water at equinoxes, since this latter is a season more cold for both so that the frostening would be summed up (as you can see on Earth, where at spring/summer's tropics there are rainy days; that rain maybe should be permanent snow for such tilted axes).
Anyhow, to reply, and premise that I do not know how the program with which you develop the polar caps works, whether in "additive" or "subtractive" form, each piece-per-month that would be subtracted from equator should be so (degrees are ice cap coverage):

180° - (90°S + x°N) is the northern polar cap at north summer solstice;
180° - (90°N + x°S) is the southern polar cap at south summer solstice;

then:

180° - [180° - (90°S + x°N) + 180° - (90°N + x°S)] / 6

will get the "empty pieces" of the ice's recession for both the emispheres rispectively, within the solstice-solstice interval (max. summed up recession at equinoxes); then fill/no fill up the pieces with ice accordingly to the months (I do not know how you do figure out the painting work).

Does it make sense?

Fenerit wrote:Sorry, my mistake: read

180° - (90°S + x°N) is the southern polar cap at north summer solstice;
180° - (90°N + x°S) is the northern polar cap at south summer solstice;

the rest is the same.

Yeah, my "opposite" latitude of choice for solstice ice cap stretch is around 20° past the equator, so, taking the first formula (south ice cap at north summer), "180° - (90°S + x°N)", I put it into my calculator "180 - (90 + 20)", and got 70. Did I do it right so far? If so, what does it represent and what do I do with the 70?

I'm using the same latitude reach for the other formula too (20°), so it is again "180 - (90 + 20)", with 70 as the outcome.

Putting the whole third formula into the calculator with my specified numbers gave me 156.6666.... (repeating). Is this correct?

(As for drawing the ice caps, I use some of the tricks provided by vliet, combined with my own personal methods. )

PlutonianEmpire wrote:"At the autumnal equinox it will be receded of 20°(6.6..°x3)" makes me think it receded by 20° and giving it a 90° (equatorial) extension, although "meanwhile forming 55° ([70°/2]+20°) of ice at pole" gives me the impression of the cap going down to either 35°N at north autumnal equinox.

I'm sorry Plutonian but the word "either" in that phrase is difficult to me to translate without misunderstanding: "either" mean: 1) "both"
2) "one of the two"
3) "or the one or the other"
4) "or the one and the other"