Celestia Forums

Since Europa surface is very smooth,does a normal map really makes sense?I think that better specular should be created.The best we have is a 4k SpecularMap,that don?t make the ice very shiny

AFAIK from the photometry, Europa isn't "specular". It's not a perfectly smooth ball of ice - at fine-scale, the surface is absolutely covered by ridges, cracks, and chaos terrain that would screw up any specular reflection.

Personally I think the best thing to do is have NO specular map at all, and the normal map would not really be worth it unless you were looking VERY closely at the surface (the maximum topography is only about 200 metres or so)

See here for more hi-res images:
http://www2.jpl.nasa.gov/galileo/images ... mages.html

I think you are right,but I have another doubt.Why Celestia can?t show fine detail in Europa like rafted terrain,"puddle" and mottled terrain.Was Europa entirely mapped?

Evil Dr Ganymede wrote:AFAIK from the photometry, Europa isn't "specular". It's not a perfectly smooth ball of ice - at fine-scale, the surface is absolutely covered by ridges, cracks, and chaos terrain that would screw up any specular reflection.

Personally I think the best thing to do is have NO specular map at all, and the normal map would not really be worth it unless you were looking VERY closely at the surface (the maximum topography is only about 200 metres or so)

See here for more hi-res images:
http://www2.jpl.nasa.gov/galileo/images ... mages.html

danielj wrote:I think you are right,but I have another doubt.Why Celestia can?t show fine detail in Europa like rafted terrain,"puddle" and mottled terrain.Was Europa entirely mapped?

At a kilometre-scale, yes. But Galileo couldn't manage to image it globally at higher resolution because of the limitations of its thrice-damned broken high gain antenna, which practically crippled the mission because it severely limited the amount of data that could be returned (by way of comparison, in the space of about a week during its Jupiter Flyby, the Cassini spacecraft returned more images of Jupiter than Galileo had in its entire mission - and at that point Galileo had been orbiting Jupiter and imaging the system for about 5 years!).

So when it got close to the satellites, Galileo had to send back small 'postage stamp' images through the low gain antenna that were high resolution but of small areas of the surface. Someone could, as Selden point out elsewhere, make a Virtual Texture like they're doing for Earth that allows you to zoom into specific areas and see higher resolution images there, but I have no idea how to do that myself.

It's not realistic but hay it looks neat and there is such a thing as artistic licences
and europa is fun to look at with a normal map

I don't think that much "artistic license" was intended with Celestia. Otherwise you'll just end up with planets in the solar system that don't resemble their real counterparts.

Fact is, you won't see topography on Europa unless you're really close. It does after all have the label of "the smoothest body in the solar system", so giving it a normal map is especially ridiculous. Otherwise, you may as well say it's OK to for Mars textures to have a neon blue surface colour.