On Saturday 21 February 2009, [email protected] wrote: > Hey List! > > I really need your help here and this thing surely is piece of > cake for you guys... > > Simply put: I wanna make a material to fade out smoothly at the > edges of the object it's applied to. > For example to make an atmosphere for a planet which has a smooth > border, fading into the void without any perceptible edge. > > Problem is - I haven't found this in the manual, haven't found > anything on the internet concerning this (except a tutorial for > making a gasflame which fades out at the top), and being more of > an "artistic dabbler" without any even halfway proper > understanding of the principles behind VSL or even rendering > itself (plus the fact that I really, really suck at math...), I > haven't found out how to do this. Though I'm pretty sure, this > should be very simple. > > I had thought, using the "linear" object under "surface > properties" with "fade" as output should do the job. Also tried a > curve, tried applying a texture map and much, much more. > I'm sure I just don't see it though it's so simple, I'd gonna > feel like an idiot should I at last come to know how to apply > this fading... > > So please, somebody out there - help me! ;-) > > > Greets > > Martin
Hi Martin, I can't help you with making a material with the sort of fade you want but for planetary atmospheres I've just used constant turbidity materials mapped to an enclosing sphere. The path length through the atmosphere is then at it's greatest when it just skims the horizon but gets smaller as the path moves out from the horizon until finally, when the path is near the 'top' of the atmosphere, the path length is very short. Basically, it comes down to the length of the chord through the atmosphere sphere; the longer the chord, the more dense the atmosphere. You can see the same effect in this image I did with Real3D V3, except in this case it's sort of back-to-front; the atmosphere is a cylinder inside another cylinder instead of a sphere outside another sphere. The same principle applies though; as you look up from the apparent horizon you end up looking through less atmosphere i.e. the path length is shorter. http://www.spatial.plus.com/V3/im_Ringworld00m02.jpg You will need to do a bit of playing around with both the size of the atmosphere sphere and the turbidity of the atmosphere material to get the right effect; iirc, the model in that image was done to about 1/1000 scale, so it's very big in absolute terms. Also, be prepared to make the atmosphere sphere a lot bigger than you might have expected, to get the effect you want. LeeE
