For upcoming improvements to Sun & Sky gadget, combine longitude and time of day into a single tweak, and add an axial tilt tweak
The "Time Gadget" item in the "In The Works" column on the Trello (https://trello.com/c/5z9OI3ON/39-time-gadget) mentions that it will also add extra tweaks to the Sun & Sky gadget to enable it to compute the sun position procedurally.
But the inputs mentioned for this feature are time of year ("date"), time of day ("time"), latitude, and longitude. Time of day and longitude being two separate inputs is redundant - the combination of the effects of those values on sun position is a simple addition. Those inputs should be combined into a single "Longitude + Time of Day" input.
Also, the three inputs - time of year, longitude + time of day, and latitude - that leaves you with aren't quite enough. There should also be an "axial tilt" input, because the effect of axial tilt on sun position doesn't combine with any other input by simple addition.
The four inputs would determine sun position like this, with innermost to outermost referring to how you would set it up if the sun were a sculpt in a nested rotation rig rotating about the scene origin. Positive rotations about an axis are anticlockwise looking along that axis, negative rotations about an axis are clockwise looking along that axis:
- Start with sun at nadir.
- Apply time of year as the innermost rotation about the positve z axis - a logic network can increase this value with time for a planet orbiting prograde, and decrease it with time for a planet orbiting retrograde.
- Apply axial tilt as the second innermost rotation about the positive x axis - a positive value makes time of year 0 the northern winter solstice / southern summer solstice, and a negative value makes time of year 0 the southern winter solstice / northern summer solstice.
- Apply longitude + time of day as the second outermost rotation about the positive z axis - a logic network can increase this value with time for a planet rotating retrograde decrease it with time for a planet rotating prograde. That mapping of positive changes to retrograde and negative changes to prograde is opposite the mapping for time of year, so an alternative convention would be to apply this as a rotation about the negative z axis.
- Apply latitude as the outermost rotation about the positive x axis - negative values are northern latitudes and positive values are southern latitudes. Alternatively, apply this as a rotation about the negative x axis to map positive values to northern latitudes and negative values to southern latitudes.
-
Having an axial tilt sounds like it would be useful, and we could have it default to whatever earth's axial tilt is if nothing is wired in? Or if it's a slider, have that be the default value.
Apart from that, well I mean... I don't know the first thing about lat/long, times, and how it all combines to produce a sun angle in the sky. So I'd definitely want simple date/time, and lat/long inputs. Then whether it's a simple addition, or some complex algebra or trig... I don't need to care about any of that for it all to work properly. I think that's the aim of Dreams in general... give the creators easy to understand tools, and let the engine worry about the implementation and how to calculate stuff. I don't think putting that on the creators would be a good move; you'd be fine obviously but I'd be lost.
I couldn't understand the steps you gave, so I can't comment on them. (An example of how confused I would be if I had to do any of this stuff by myself. XD)
-
Yes, all of that math would be something that the Sun & Sky gadget does internally. I only included it to illustrate where the input that they missed - axial tilt - would fit into the process of calculating the sun position. Earth's axial tilt as the default value for the axial tilt input would also be a good idea - but you might want an exception to the rule that making the first wire connection defaults to modulate blend mode when the tweak has a non-zero value. As for date and time inputs, I assumed that the Sun & Sky gadget's date and time inputs would be numbers in the range 0.0 to 1.0. But remember that these Sun & Sky gadget improvements were first mentioned in the Trello item discussing a Time gadget for working with real world times. That gadget would probably have inputs for a 24 hour clock time and a Gregorian calendar date, which it would use to calculate outputs that can be wired to the Sun & Sky gadget's time of year and time of day. Considering this, keeping longitude and time of day separate would make sense.
iniciar sessão para comentar.