Hi!

At the moment I'm working on a simple simulation of an Earth-orbiting spacecraft. This involves centring the camera on my spacecraft which is orbiting a few hundred kilometres above Earth and simultaneously rendering the planet itself out to a distance of around 12000km. Of course, it's unfeasible to render such a scene using metres as my base unit, as I have to specify the spacecraft's position in hundreds of thousands of metres relative to the centre of Earth, and using such massive numbers to position objects in Direct3D seems to cause problems.

So, my question is: how would you approach the problem of rendering small scenes embedded in much larger ones? Should I render the Earth first followed by the spacecraft using different units each time? If you know of any useful articles or tutorials, that would be great :)

Thanks!

typically, when a scene is bigger than a float can hold accurately, objects are defined in "world coordinates" which are then converted to camera-relative floating point coordinates for drawing. objects which are still too big/far to fit in a float get scaled down in both range and size until they fit in a float. drawing would probably be done in two passes, first a pass to draw all objects too big/far to fit in a float, then a pass to draw all closer objects. near and far planes can be reset as you go, to keep zbuffer resolution high.

this recent thread touches on these issues:

http://www.gamedev.net/topic/661933-max-size-for-level-using-floats/

probably not much help but pretty cool all the same:

http://www.andrewtop.com/Projects/Linfinity

also might be worth looking at the answer to this q:

http://stackoverflow.com/questions/1930421/seamless-transitions-of-scale-over-large-distances-3d-rendering