all material emulation, your end result is only as good as the source material
you use, so therefore search the Internet for reference photographs of the Earth
from space. Nasa has a huge library of Earth photography taken from orbit, but
bear in mind that each one differs from the next; the Sun may be in a different
position, atmospheric conditions may be different and the camera position may
be closer or further away from the atmosphere; all of which can alter the colour,
contrast and brightness of the end result so choose carfully.
these photos we can observe that the Earth is not completely shiny; it varies
depending on the surface being viewed. The sea is obviously highly refective,
while ice-capped mountains are less so, down to the land which has virtually no
value at all. Therefore a shininess map should be created to accomodate this;
this should be an amended version of the main diffuse map with the sea having
the highest value (ie closer to white) and the land the lowest (ie closer to black).
viewing close to the surface, we will want to introduce a bump map to give the
sea some texture; this noise procedural texture should be masked with another
amended version of the main Earth map so everything apart from the sea is masked
out. When creating outdoor scenes, additional realism can be added by adding fog
atmospheric effects to desaturate the image the further the object is from the
camera. The same principle applies here. Using a falloff map, the Earth map should
be mixed with an additional map that has had all colour removed to generate this
impression. This also give the impression of a living world with atmospheric conditions.
Elements of habitation could be included as pinpoint lights where major cities
and routes exist.
clouds should cast shadows onto the surface, so you shouldn't really mix the cloud
map(s) with the earth map(s). By creating a clone of the earth sphere and scaling
it ever-so slightly, we can then apply our cloud material. However, a single opacity
map will not suffice if the clouds are to be viewed at a close angle. Therefore,
like the sea surface, a procedural noise or smoke map should be masked out with
the cloud's opacity map as to give the appearance of depth when the camera is
close to the cloud layer and is viewing them at an angle. This will also add additional
detail to the map.
falloff should be introduced to give the impression of the thick atmosphere. This
should be created to cover both earth and cloud spheres, so an additional clone
of the earth sphere should be created and scaled to be just slightly bigger than
the cloud sphere. A totally transparent material with no shininess applied with
a fresnel map assigned to the opacity slot should be applied to the atmosphere
end result is only as good as your materials and lighting (which should have a
high soften edge, slight contrast and cast raytraced shadows to cast the cloud
map's shadows); a good high quality earth map should be used and the same applies
with the cloud map, but this can be an amalgamation of multiple maps to generate
finer detail at close quarters. Finally, you may wish to slightly colourise the
image slightly and amend the brightness and contrast by adding relevant render
individual components that build up the earth map and cloud layers|
final render with all elements applied to the three spheres that make up the final
published: 3D World magazine,
Issue 19, December 2001.
Draper, December 2001. Reproduction without permission prohibited.