Ron Parker wrote:
> On Mon, 07 Jun 1999 21:19:54 -0500, Bob wrote:
[snip]
> >The person originally wondering about "smoothing" a HF further would seem correct
then
> >about possibly interpolating via spline between the intitial triangle creation and
> >producing a further tessalation.

That person was me, incidently. I have a post in povray.bugreports
(didn't know a the time where else to post), and Bob and I have further
conversed about it in povray.general.
My problem is that I'm using a large-scaled height field to simulate
sand dunes, and the camera is down within the height field itself. This
proximity apparently aggravates a nasty problem with the surface normals
of the triangles, causing some to shine out brightly because they face
the light; they look like marching diagonals of checkerboard squares.
Smoothing only blurs them; it doesn't eliminate them, as it should.

> An interesting idea would be to implement a heightfield as a mesh of bicubic
> patches.  It'd be a memory hog, but it would probably look very good.

I had proposed a more aggressive smoothing algorithm which would do the
job for me--simply making the triangles look even less flat, causing
more bending toward the outer normals. But even better, I like Peter
Popov's idea of adaptively sampling the height field and
interpolating--indeed, I suggested something similar myself in the
thread on povray.general (Not-so-smooth height field).
Although I've considered changing to something like bicubic patches, the
problems in that are many. The height values would have to be
individually calculated from the existing height field data (how, I have
no idea) and thrown into the scene file as text; for a 1200x1200 height
field (which, granted, I could probably scale down considerably if I
used bicubics), that's a bit excessive.
It seems to me that some sort of automatic interpolation function--only
used when called for, of course, to speed rendering time--would greatly
improve the quality of height fields without requiring that kind of
effort. Or, even something as simple as more smoothing would do the
trick, at least in my case.

Lummox JR

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