R help - Nov 2013 - how to derive true surface area from `computeContour3d' (misc3d package) -- follow up

regarding my previous mail for this topic, I have in the meantime  
identified my misconception.


actually, `computeContour3d' returns the vertices just fine in the correct  
coordinate frame.

the misconception was caused basically by assuming that the `level'  
argument was a fractional
threshold relative to the maximum of the array. so I believed that the  
rendered cube actually
is the "outer surface" of the defined object in the example provided
in
the manpage.

I know understandt it's an absolute level and
`example(computeContour3d)'
consequently displays
some "interior" isocontour. this explains all my apparent errors.

I believe the manpage would benefit from a slight clarification that  
`level' actually is
an absolute, not a relative/fractional threshold.

apologies for the noise.

j.

ps: it of course would still be nice, if the surface area (or a vector  
containing the individual triangle areas)
were returned to the caller as well ...

On Fri, Nov 8, 2013 at 1:01 PM, j. van den hoff
<veedeehjay at googlemail.com> wrote:

> ps: it of course would still be nice, if the surface area (or a vector
> containing the individual triangle areas)
> were returned to the caller as well ...
 Does the 'surfaceArea' function in the sp package do what you want?
It's Edzer's integration of an R function that I wrote that calls some
C code that someone else wrote that implements an algorithm from 2004.

 You just need to coerce your grid data into the right form.

 Barry