[vtkusers] Frustum Culling

[David E DeMarle]

Have you tried vtkExtractSelectedFrustum?

On 3/6/07, Michael Knopke <Michael.Knopke at gmx.de> wrote:
>
>  Hi,
>
>
>
> I'm trying to write a new vtk-filter that can crop-out (set scalars to
> fixed value e.g. 0) selected volumes (e.g. inside of BoxWidget).
>
> Unlike all other cropping filter I know, will this filter work with
> vtkImageData and preserve topology and geometry. This means it will not cut
> cells.
>
> Therefore I'm trying to implement frustum culling (with the planes from
> BoxWidget) and later add octree to speed up calculation.
>
>
>
> The problem I have is regarding detection if the point that is evaluated
> lies behind the plane. As far as I know, one has to calculate:
>
>
>
> 1). Shortest distance to plane (this works well)  à returns
> PlanePointDistance
>
>
>
> 2). Add this distance to the DotProduct of ( PointX, NormalOfPlane):
>
>
>
>    Result = PlanePointDistance + (vtkMath::Dot(PointX, Normal));
>
>
>
> 3). If result is negative than pointX lies behind Plane
>
>
>
>
>
> Unfortunately this yields wrong results. Does anybody know what's wrong?
>
>
>
> Michael
>
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