On Tue, Jun 8, 2010 at 5:03 PM, Jonathan Gutow <[email protected]> wrote:
> I'm working on a slicer tool and want to make sure I'm clear about how
> planes are defined within the transform manager as I want to adjust the slab
> and depth planes in real time based on user input. Here's my understanding.
>
> 1) Planes are defined by point4f's where the x, y, z coordinates define a
> vector from the origin that is perpendicular to the plane.
> 2) I assume the plane includes the point at the end of the vector.
> 3) I'm most confused about the meaning of w (the fourth coordinate) for
> planes that are not parallel to the screen surface, but fixed in the
> molecule coordinate system.
>
> Can anybody clarify?
>
>
plane: ax + by + cz + d = 0
"w" is "d". Then the distance to the origin of the plane is
d / sqrt(a^2 + b^2 + c^2)
and
d is the length of the vector (a, b, c) times the directed distance of the
plane to the origin.
So in xyzw notation,
w is the length of the vector (x,y,z) times the directed distance of the
plane to the origin.
BOb
Thanks,
> Jonathan
> Dr. Jonathan H. Gutow
> Chemistry Department [email protected]
> UW-Oshkosh Office: 920-424-1326
> 800 Algoma Boulevard FAX:920-424-2042
> Oshkosh, WI 54901
> http://www.uwosh.edu/facstaff/gutow
>
>
>
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