RE: [Algorithms] Rendering (a portion of) a Plane

[Jeremy B. <Jer...@in...>]

Actually what I'm more after is all these frustum culling routines
I've seen lately that extract the clipping planes from the
modelview and projection matrices I'd like to be able to extract these
draw them (at least a portion since a plane goes to infinity)
and move my eye position elsewhere to test if things really are getting
culled outside (I learn better when I can observe what's happening
visually, dunno I just have a hard time trusting my code... I'd lie to know 
I'm going in the right direction before getting in too deep)
even an example of how to draw a few points on the plane so I can see it 
visually would be great... is that a better description of what I'm going
for?

Jeremy Bake
RtroActiv 

> Hmm,
>
> Your equation:
> Normal[0] * X + Normal[1] * y + Normal[2] * z + distance = 0
>
> is defining 3D space as an infinite number of parallel planes with the
same
> Normal as in the equation:
> Normal[0] * X + Normal[1] * y + Normal[2] * z = 0
>
> using an index of distance to determine which parallel plane you are
> referencing.
> Normal[0] * X + Normal[1] * y + Normal[2] * z = -distance
>
> Correct me if I'm wrong, but it sounds like you want to find points ON the
> plane...if you are trying to describe a circle on the plane then you want
> all points (x,y,z) which lie on the plane and which are the same distance
> from your point of origin (x',y',z').  If you like matrices and
> transformations then perhaps use the 2D (x,y) coordinate plane to find
your
> points x^2 + y^2 = distance, then translate and rotate them onto your
plane.
>
> R&R
>
>
> > -----Original Message-----
> > From: Jeremy Bake [mailto:Jer...@in...]
> > Sent: Friday, July 21, 2000 6:57 AM
> > To: 'gda...@li...'
> > Subject: [Algorithms] Rendering (a portion of) a Plane
> >
> >
> > I've been working on my viewport culling and I just wanted to
> > test something
> > out
> > I was wondering if anyone could tell me how to render a
> > portion of a plane
> > around
> > a particular point using the
> > Normal + distance version of a plane.
> > I think it relates to
> > Normal[0] * X + Normal[1] * y + Normal[2] * z + distance = 0
> > but I can't seem to get my head around how I could draw this function
> > over a specific range...  any help would be Greatly appreciated
> >
> > Jeremy Bake
> > RtroActiv
> >
> > _______________________________________________
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> > http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> >
>
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thanks!!!!!!!

mauro


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