In article <3f1db4da@news.povray.org>, Wolfgang Wieser <wwi### [at] gmxde> 
wrote:

> Well, I was actually waiting for someone to come up with a better 
> blob because each time I model some blob object, I was unhappy with 
> these somewhat ugly lines caused by the linear falloff function. 

This seems to be a common misconception...the blob falloff function is 
not linear. The function given in the documentation is:

strength*(1 - (distance/radius)^2)^2

The problem is that it has non-0 second derivative when distance/radius 
equals 0, which is at the very edges of the blob components where the 
function gets chopped off. Because of this, while the surface is 
continuous, it has abrupt changes in curvature. The function I used for 
the blob2 object is:

((6*r - 15)*r + 10)*r*r*r

which is equivalent to:

6*r^5 - 15*r^4 + 10*r^3

with r = distance/radius in the first equation. It has a second 
derivative which is 0 at r = 1, and seems to give a more fluid, less 
chunky looking shape as well. This function actually comes from a recent 
update to the Perlin noise algorithm which fixed a similar problem that 
resulted in grid artifacts.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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