RE: [Algorithms] visualizing frustum planes?
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RE: [Algorithms] visualizing frustum planes?
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From: Akbar A. <sye...@ea...> - 2000-08-22 08:42:03
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i haven't been following this thread to closely.
but.
nate robbins has made a set of tutorials for all the eye camera,
tweakable settings, "learning material", etc..
if you look on google you are sure to find his site.
he is also mentioned in the red book as well.
prob in the beg < pg 30 .?
heh-
i'm sure someone has already told you about him.
sorry if it's a repeat.
peace.
akbar A.
"We want technology for the sake of the story, not for its own sake. When
you look back, say 10 years from now, current technology will seem quaint"
Pixars' Edwin Catmull.
-----Original Message-----
From: gda...@li...
[mailto:gda...@li...]On Behalf Of
Pallister, Kim
Sent: Tuesday, August 22, 2000 12:39 AM
To: gda...@li...
Subject: RE: [Algorithms] visualizing frustum planes?
Also, if you are on DX7 or OpenGL 1.1, you can download the eval version of
GPT from Intel's web site. It include's a 'wide angle' and 'reverse wide
angle' view that will do this transparently for you. Just run the EXE
through it and voila.
Kim Pallister
We will find a way or we will make one.
- Hannibal
> -----Original Message-----
> From: Michael S. Harrison [mailto:mic...@ud...]
> Sent: Monday, August 21, 2000 11:31 AM
> To: gda...@li...
> Subject: Re: [Algorithms] visualizing frustum planes?
>
>
> Duh. This is precisely the reason I like working on teams
> where more than one person is familiar with a given system.
> Sometimes having someone state the obvious is a good kick in the seat.
>
> It hadn't even occurred to me to use an artificial model
> matrix and draw the simulated frustum planes, in order to
> check (and help visualize) the camera math
>
> At 07:10 PM 8/21/00, you wrote:
> >Hey,
> >
> >Here's a piece of code which will render the camera frustum,
> which I find to
> >be useful when hunting camera problems. It works best when
> viewed from a
> >second camera though (since the frustum is mostly clipped by the very
> >frustum planes it is meant to visualize), with the AABB
> culling code (or
> >whatever you may end up using it for) hardwired to the first
> camera - only,
> >the second camera should just render everything, or only
> rely on culling
> >code of which you're certain that it works.
> >
> >----8<----
> > float ax, ay, bx, by, fx, fy;
> > static Vertex verts[8];
> > static ushort indices[24] = {
> > 0,1, 1,2, 2,3, 3,0,
> > 4,5, 5,6, 6,7, 7,4,
> > 0,4, 1,5, 2,6, 3,7
> > };
> >
> > // Calculate fov/2 angles in x and y direction.
> > ax = mFov / 2;
> > ay = ax * ((float) mViewport.height / (float) mViewport.width);
> > // Calculate x/y coordinates of the front plane.
> > fx = mFront * (float) tan(ax);
> > fy = mFront * (float) tan(ay);
> > // Calculate x/y coordinates of the back plane.
> > bx = mBack * (float) tan(ax);
> > by = mBack * (float) tan(ay);
> > // Setup frustum verts.
> > verts[0].loc.set(-fx, +fy, mFront);
> > verts[1].loc.set(+fx, +fy, mFront);
> > verts[2].loc.set(+fx, -fy, mFront);
> > verts[3].loc.set(-fx, -fy, mFront);
> > verts[4].loc.set(-bx, +by, mBack);
> > verts[5].loc.set(+bx, +by, mBack);
> > verts[6].loc.set(+bx, -by, mBack);
> > verts[7].loc.set(-bx, -by, mBack);
> > for (short i = 0; i < 8; i++)
> > verts[i].color = Color3(0.8f, 0.8f, 0.8f);
> > // Render frustum.
> > GfxDevice->SetTransform(eTransformWorld, mMatrix);
> > GfxDevice->Draw(GfxDevice::PrimLineList, verts, 8, indices, 24);
> >----8<----
> >
> >If you have any questions about the specifics of the above
> code, mail me
> >offline.
> >
> >HTH
> >
> >Jim Offerman
> >
> >Innovade
> >- designing the designer
> >----- Original Message -----
> >From: "Michael S. Harrison" <mic...@ud...>
> >To: <gda...@li...>
> >Sent: Monday, August 21, 2000 9:18 AM
> >Subject: [Algorithms] visualizing frustum planes?
> >
> >
> >> I'm attempting to implement the AABB culling code talked
> about here some
> >time ago and I'm running into a general problem in
> visualizing the frustum
> >planes used to cull objects based on their AABB's
> >>
> >> I'm using both Klaus Hartmann's AABBCull sample and the
> Viewcull sample
> >included with the OpenGL FAQ.
> >>
> >> While the code generally works, I'm having some difficulty
> visualizing the
> >relationship between the plane vector and the "distance"
> value stored with
> >it, which I'm sure is the reason I can't quite figure out
> why the code
> >generates intersection results when it should generate a full cull.
> >>
> >> As you might guess, I'm fairly new to the world of 3d
> projection and I'm
> >still wrapping my mind around all the transformations that
> take an object
> >from "world" space to screen space.
> >>
> >> Can anyone suggest a reference or way to visualize exactly
> what's going on
> >with the plane extraction and how the vectors relate back to
> the AABB?
> >>
> >>
> >> _______________________________________________
> >> GDAlgorithms-list mailing list
> >> GDA...@li...
> >> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >>
> >
> >
> >_______________________________________________
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> >http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
>
>
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