>
> Unfortunately, we are only scratching around the edges for improved
> performance using the existing technique, and really we need to try
> something a bit more radical.
I read that X-Plane 10 is using a complete new system for clouds (LOD
based):
I haven't seen this in action, and don't know how good this really is.
But this is definitely some food for the brain.
Here is what they write:
So, how do we render these clouds in x-plane 10?
>
> the answer is levels of detail, which is a display of resolutions of
> buckets.
>
> we have a HIGH resolution of cloud geometry. each puff is 1 meter across.
> BUT, those puffs only go out, say, 10 meters.
> in other words, sure: you can see cloud puffs that are 1 meter across. but
> you can only see them up to 10 meters away.
> you see the small, detailed puffs up close only.
> that ain't many puffs. just 10x10x10, or 1,000 puffs. we can handle that.
>
> then, for puffs that are 10 meters away to 100 meters away, we draw puffs
> that are 10 meters across!
> how many puffs to fill that space?
> well, we have 1 puff every 10 meters, we go out 100 meters in visibility
> for a moment, so that is 10 puffs north/south x 10 east/west x 10 up/down,
> for 1,000 puffs.
>
> hhmmm...
> we just covered 10x the space, but without using the exact SAME number of
> puffs as we did for the smaller area, by making each puff bigger.
>
> sure, the bigger puffs are less detailed, but since they are farther away,
> you could not see the 1-meter-diameter puffs anyway... they are too far
> away to see when they are that small.
>
> then, from 100 meters to 1,000 meters, we draw puffs that are 100 meters
> across.
> we have 1 puff every 100 meters for 1,000-meter range.
> that is that is 10 puffs north/south x 10 east/west x 10 up/down, for
> 1,000 puffs.
>
> again, only 1,000 puffs.
> BUT, we are covering a full kilometer! the better part of a mile!
>
> how about we go out 100 kilometers???
> each puff is, say, 10 kilometers across if drawn so far away.
> that is 1 puff every 10 kilometers for 100 kilometers.
> so that is 10 puffs north/south x 10 east/west x 10 up/down, for 1,000
> puffs.
>
> AGAIN!
> NO MATTER HOW BIG THE SKY, EACH LEVEL OF DETAIL ONLY COSTS US 1,000 PUFFS!
>
> 7 levels of detail is plenty of detail.
> we call each level of detail a 'resolution'.
> so 7 resolutions gives 1-meter wide puffs of close, and huge puffs very
> far away, as seen from orbit!!!
> and we wind up with: 7,000 puffs.
>
cheers,
Robert
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