On Sun, 07 Nov 1999 00:45:33 -0800, Ken wrote:
>
>
>Peter Popov wrote:
>
>> A height_field *is* solid -- it extends from its surface down to the
>> x-z plane.
>
>That is a bit misleading Peter. While HF's are solid from the point of
>view that they may be used in CSG operations because pov can clearly
>determine their inside and outside for all practical purposes they
>are not really a solid object in as much as they are a triangle mesh
>object that much more closely resembles a shell of an object and not
>a solid object like a box or a sphere would be.

Wow, that's a long sentence.  AIs must not need to breathe. :)

No, what's misleading is that he gave the wrong bounds for the thing.
A point is "inside" a height field if its Y coordinate is less than
the Y coordinate of the height field at that X,Z location.  That is,
the inside extends from the surface to the X-Z plane, and all the way
along the -Y axis.  Try intersecting one with various size boxes to 
see this for yourself.

A height field is no more and no less solid than an "open" cylinder
or a clipped object.  It can do weird things with interiors like IOR
and media, but it works in CSG.  Contrariwise, there are objects that
are solid in how they work with interiors but don't work in CSGs: 
closed meshes and closed unions of patch objects both fit this criterion.
The word "solid" is hopelessly confusing to a POV user, so I try to 
avoid it altogether.

-- 
These are my opinions.  I do NOT speak for the POV-Team.
The superpatch: http://www2.fwi.com/~parkerr/superpatch/
My other stuff: http://www2.fwi.com/~parkerr/traces.html

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