[GRASS5] bugs

Justin Hickey jhickey at hpcc.nectec.or.th
Thu Jan 18 01:54:58 EST 2001

Hi Helena

Helena Mitasova - staff wrote:
> I believe you have SGI - have you ever tried NVIZ?
> Do you get the same problem, which I now believe is
> a bug that for certain combination of viewing position,
> zscale and resolution parts of the surface are masked out?
> it gets worse when you zoom out and when the file is big -
> (say 1000x1000). Bill was supposed to look at it but
> he still seems to have troubles with his computer.
> It worked Ok with the GL version, but OPEN GL
> calls are different - do we have an OPEN GL expert who could
> look at it? Bob (Covill) do you have anything new about
> this bug?

Yes, we are using an SGI here. I'm not sure if I replicated "the bug" or
not. After loading in a large surface (2300x2500) I increased the z
exaggeration to about 35 and most of the map was dark. It appeared to be
only a small portion of pixels were being rendered with bright colors
but the rest were all dark. Then I played with the lighting and found
that clicking "Follow ViewPoint" and then clicking the surface button,
rendered the surface properly. However, clicking "Follow ViewPoint"
(disabling it) and rendering again had no effect. Decreasing the z
exaggeration had no effect but increasing it again caused the same
problem. So, it appears that this problem is a lighting problem. Is this
the type of behavior you are experiencing?

BTW, I wouldn't call myself an OpenGL expert, but I am quite familiar
with it.

One thing I noticed is that we may want to change the lighting controls,
they do not seem very intuitive to me, but that's just my opinion. Also,
it seems that interrupting the render process is not truly interruptive.
While playing around with the lighting I interrupted the render many
times, yet when I stopped and let the render finish it flashed between
wire frame and rendered surface several times. This seems to indicate
that the commands were being queued somehow.

Anyway, I don't have a lot of time right now to look into this, I might
be able to take 1/2 a day or so.


Jazzman (a.k.a. Justin Hickey)  e-mail: jhickey at hpcc.nectec.or.th
High Performance Computing Center
National Electronics and Computer Technology Center (NECTEC)
Bangkok, Thailand
People who think they know everything are very irritating to those
of us who do.  ---Anonymous

Jazz and Trek Rule!!!

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