Part 2 - Falling through space

Scott Manley

OK, next step is a small sequence of the asteroid flying past us. We start out falling towards the planet Earth at ~16.5 kilometres per second looking at the asteroid falling towards the earth at 17.5 kilometres per second. It passes us after about 30 seconds and the camera turns to follow it.

The Earth is a sphere with a suitable targa image of the continents mapped onto it. A layer of clouds is also added - 5km is probably too high to be totally realistic but I wanted to have some clouds catching illumination where the land was below the horizon. The clouds are basically another sphere with a sutable noise function mapped onto it and with a colour map which is transparent in places.

The view in the image is from an altitude of 5000 km so many of the continents look distorted compared with the view from infinity which most people are used to - this is perfectly normal.

The illumination is provided by an area light, which is about 5 times larger than the real sun would be, to provide a much smoother terminator than the 'physical' source would give. In real life we have the atmosphere to help carry light over the horizon but no raytracer I know of will implememnt this secondary illumnation and even if it did the CPU time required would be unrealistic when compared with this solution.

Initially we start with our camera pointing away from Earth looking into deep space, pointing at an asteroid approaching us at about 1 kilometre per second. As it passes us the camera tracks it to see it falling towards Earth (although you have to rememebr that the camera is falling to Earth at almost the same speed).

Some rotation was also added to the camera - partly to make the scene more interesting, but also to give a better impression of falling. The time at the top of the image was added with a little program I wrote using jpeglib.

• 60 second mpeg movie of flyby

Last Revised: 2009 November 10th