chris wrote:Basic two-source lighting is trivial . . . The difficult part is dealing with all of Celestia's vertex and pixel shaders, adding two light source versions of each one. Making shadows (eclipse and rings) work with two light sources will require a significant revision to Celestia's lighting, Unless you've spent some time writing 3D graphics code in the past, I don't think you'll have much luck modifying Celestia's renderer to add support for multiple light sources.
I probably wouldn't
. So having another light source isn't as simple as just letting the code run and seeing what comes out? You'd actually have to change things quite significantly?
chris wrote:I deliberately avoided adding light source attentuation . . . The limited dynamic range of CRT and LCD monitors makes it rather less interesting than you'd think . . . Consider that Uranus's mean distance from the Sun is 19AU, so it should appear about 1/400 as bright as Earth. With 32-bit color, you only have 256 representable brightness level, so Uranus would be completely black! However, the human eye can adapt to remarkable range of light conditions, so if you were actually looking out the window of a spaceship passing by Uranus, it would be plainly visible . . . Linearly scaling the brightness is not the right thing to do; a logarithmic attenuation might be reasonable though. One final thing to consider: a full moon is 1/100,000th as bright as the Sun, yet it's very easy to see by its light--on a hypothetical planet 100AU from the Sun there would still be ten times as much light!
That's a point, I hadn't thought of the pixel limitation of the screens... good point about the full moon though.
chris wrote:Is all of the 476 W/m2 of brown dwarf radiation in the visible spectrum? Even at 2000AU, I'd be very suprised if Antares didn't outshine the brown dwarf in the visible.
Dunno. I think that's the total luminosity over the whole spectrum, but I suspect most of it will be in the near IR/red end. Then again, so is Antares' luminosity, since that's a big M5 Ia-b supergiant (though it's at 3000K, rather than 1600K of the Dwarf). Hmm. I doubt if only 1% or so of the Dwarf's luminosity would be in the visible spectrum though, it'd probably be more than that.
I might as well post a piccie of it while I'm here. This is the best I've managed so far:
http://members.shaw.ca/evildrganymede/a ... tares2.jpg
The planet's the little purple ball in the lower-middle, and Antares is the big red glow in the top right (the Dwarf is the big thing in the left of the picture, obviously). I put a lightsource inside the Dwarf to illuminate the planet, and Antares is a 'fake star' (not emitting any light) that is 5 AU in radius orbiting the Dwarf at 2000 AU.