Thorsten > > There are good sources for sea colour out there - here is one: > > > > > http://oceancolor.gsfc.nasa.gov/FEATURE/IMAGES/A2008129125500.Scotlan > d > > .png > > > The Northern North Sea, away from the turbidity and major river > > outfalls of the Southern North Sea, is indistinguishable from the > > Atlantic, the other side of Scotland. > > 4 West, 54 North I get an rgb value of (93, 113, 121) > 2 East, 54 North I get (31, 71, 83)
2 E 54N? that's the Southern N Sea off the Humber estuary. That is one of the major sources of silt flowing into the North Sea . The depth is probably less than 150m there. 4 W 54N? That's just off Morecambe Bay, which forms part of the Irish Sea. It is the largest expanse of intertidal mudflats and sand in the United Kingdom! Neither of these locations could be remotely described as deep ocean, and yes, we should certainly be investigating how to best model such areas of sea. > There's pretty significant variation everywhere, but I don't see that in that > picture that the two would even be similar. > > > There are many examples in this archive, and if there are differences > > in the deep ocean colour in any of the oceans they are darned hard to > > spot. Similarly, if there is a difference between the Atlantic and the > > Mediterranean, it's very hard to see. > > We might not be after the same thing here... > > In reality, water color depends on a lot of factors: > > * light reflection at the surface, i.e. light diffuseness, intensity, wave > patterns, sky color, ... > -> we have a decent way to account for that in the shader > > * sediment and algae in the water > -> water being a flowing substance, all these are variable phenomena, > -> rivers carry a lot of mud in spring when the snow thaws, algae bloom > -> seasonally,... we can't model this realistically in any case > > * near the coast, depth and nature of the bottom > -> white underwater sand looks quite differently from overgrown rocky > bottom, deep water looks different from shallow water... we simply don't > have this information - we might get depth somehow, pass true depth to the > shader, use it to determine color, then let the shader move the vertex up to > the water surface, but it's a bit tricky. Yup - getting to grips with all that is difficult. Not too dissimilar to getting reasonable representations of towns and countryside in various regions in the world, I suppose > Given that we can't do so much realistically anyway for lack of data (and lack > of framerate - I could probably write a detailed water color computing code, > but that'd really drive framerate down), my idea is more to re-create iconic > pictures. > When approaching Nice in sunshine, I want to see one of these postcard > Cote d'Azur pictures. When landing on a drilling rig in the Northern Sea, I > don't expect to see this deep blue. Probably in reality the differences are > driven by differences in lighting, average weather and some sediment/algae > component - but when I can't do the realistic thing, I might as well do the > iconic thing. > > Many people (including myself) seem to feel that the sea should look > different in different places. I'm entirely willing to tweak physics here a bit to > create a better illusion that one is in the place by fulfilling the expectation. > True, the actual Caribbean deep ocean is not turquoise. Then again, the > actual Caribbean city doesn't look the Flightgear way either. But making sea > color a lighter turquoise in the Caribbean helps me to maintain the illusion > that I am in the Caribbean rather than the Northern Sea. > > Feel free to disagree, but for me creating the visual environment has much > more to do with credible illusions than with getting the physics of the scene > right (disclaimer: my position is diffferent for the fidelity of the FDM where > we can actually get the physics really right since we have often the required > amount of data). I do feel free to disagree - the Caribbean just isn't turquoise, as you say. There was a time when we prided ourselves on FG being the most realistic sim around. Making the ocean the wrong colour to maintain an illusion just doesn't seem to me to sit right with that. But I would also agree that we need to sort out some of the more obvious problems of the shallow seas, if that is possible. Anyway, on a more prosaic note - your sea colour script appears to be bugged here. After I got it to run (my bad, I broke it) I discovered that it iterates at 1 sec not 5 as stated. If I restart Advanced Weather the sampling locations are re-added to the interpolation_vector which grows in size: I have reached 32 so far, but sometimes FG crashes before that point. In any case running Advanced Weather FG crashes here at some point, running out of memory. I would be surprised if this were related to sea-colour, and might indeed be a general problem which Advanced Weather runs into sooner than Basic Weather. You re-instantiate "var ppos" in each of your locations: nasal doesn't seem to mind, but I wouldn't have thought that was good practice, or necessary. There seems to be an additional parameter in the St Maartens definition. And finally, I was caught a couple of times forgetting that Advanced Weather needs starting and stopping when switching between it and Basic Weather. I wish I could run Advanced Weather here - the frame rates are not at all bad, but the stagger in the frame rate is too much, and seems to give me a headache. The appearance is very good though, and works particularly well around TNCM. I hope we can get a nice even frame rate in due course. HTH Vivian ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. 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