Re: C++ cliptexures...

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Don Hatch (hatch++at++hell.engr.sgi.com)
Mon, 6 Apr 1998 16:11:12 -0700

On Apr 6, 10:40am, Jan Barglowski wrote:
> Subject: Re: C++ cliptexures...
> Jan Barglowski wrote:
> > I've created a virtual cliptexure callback that works when used in
> > conjunction with clipfly. When I took this function and put it
> > into perfly, my virtual cliptextures no longer work! I've printed
> > out the values for VirtualLODOffset, NumEffectiveLevels, and LODRange
> > and they are identical for both programs.
> >
> > My symptoms are a rapid sharpening/blurring of the virtual cliptexture
> > when zooming in or out towards it. It doesn't seem to matter what
> > speed I zoom at. Since the numbers calculated for the above parameters
> > work with clipfly, I'm assuming I'm doing the calculations correctly.
> > And when I comment out the tile-by-tile cliptexture updates, the
> > cliptexture acts as if it's on Level=0.
> >
> > I think this is one of two things:
> > 1) Clipfly does something for virtual cliptextures that perfly
> > doesn't. And I can't find what this is! I looked at the README
> > file for clipfly, and the consideration for viewpoint update
> > shouldn't cause this (am I right?). The only thing I can figure
> > is some of the parameters that control cliptextures are getting
> > some (important) initialization in clipfly. Yet I look at
> > virtcliptexture.c and don't see a lot of these values getting
> > set at all. Any ideas for what I'm missing?
> > 2) the C++ cliptexture functions don't work, but I'd hate to think
> > this is the case. Still, anyone do virtual cliptextures with
> > C++ bindings out there?
> >
> > Any hints/help/insight will be appreciated!
>

> Well, I figured this one out. In my C code is used the pfuSetVirtualParams().
> The C++ man pages do not list an analogous function!

??
I don't think we have any such function...
do you mean pfApplyClipTextureVirtualParams()?
Neither this nor its C++ equivalent is in the man page :-(
Sorry, we blew it and didn't make man page entries for:
        pfClipTexture::applyVirtualParams()
        pfClipTexture::applyClipCenter()
Their purpose and functionality is analogous to those of:
        pfTexture::applyMinLOD()
        pfTexture::applyMaxLOD()
        pfTexture::applyLODBias()
which are described in the pfTexture man page.

You'd use them if you want to change the parameters
multiple times per frame (like the .ct scene loader does).

Make sure you have read the following, which describes
how to use all of these functions and when you'd want to:
        /usr/share/Performer/doc/clipmap/HowToDoVirtual.html
There is a C example in:
        /usr/share/Performer/src/pguide/libpf/C/virtcliptex.c
Also, you already found the .ct loader source (which sets
the values multiple times per frame)-- there is
also the .spherepatch loader (which only sets the values once
per frame, using a simpler interface, if that works for you).

Don

-- 
Don Hatch  hatch++at++sgi.com  (415) 933-5150  Silicon Graphics, Inc.
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