Re: Intersections with lines and points under Performer?

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Nicolas Gauvin (nicolas++at++cae.ca)
Fri, 27 Oct 1995 16:00:53 -0400

On Oct 27, 9:20am, Michael Jones wrote:
> Subject: Re: Intersections with lines and points under Performer?
>
> It's not in Performer 2.0, and is not scheduled for 3.0 but we
> could look at that. I have a question about the feature. Such
> intersections require the construction of a volume (cylinder or
> cone, parallelpiped or frustum) about the intersection ray that
> database objects are then classified against. The cylinder and
> cone (for ortho and perspective, resp.) style provides an "is
> there a point within an n-pixel circle" type of picking result,
> while the squarish volume gives picking within an NxN screen
> aligned square. Is one of these shapes more appropriate to your
> application than the other?
>

Maybe I should have been more specific. I was thinking about picking a point
or a line with the mouse using the pfChanPick function only. Not in the more
general sense of intersecting from anywhere in the database. Isn't that as
simple as converting the vertices present in the viewing frustum to screen
coordinates using the current viewing transformation and checking if the
resulting 2D coordinates fit within a tolerance rectangle or radius of the
mouse positions?

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