[vtk-developers] New feature: improved hover support

[Jeff Baumes]

Basically yes. The exception is the render caused when the actual hover text
changes and the scene needs to be re-rendered, in which case the pick render
is not performed. The problem is knowing when a render caused any pipeline
updates or camera changes, which are the cases where you need to re-generate
the pick map. BTW the cached pick map is also used for drag-selections.
Thinking about it, it would probably be better to wait for the first "mouse
dwell" or drag-selection to update the pick map, I'll make a note of that.
Jeff

On Wed, Sep 9, 2009 at 11:27 AM, Moreland, Kenneth <kmorel at sandia.gov>wrote:

>  Does that mean every still render is actually rendered twice with the
> second one basically a pick render?
>
> -Ken
>
>
>
> On 9/9/09 9:04 AM, "Jeff Baumes" <jeff.baumes at kitware.com> wrote:
>
> I've just checked in a change that allows improved hover support in
> vtkRenderView subclasses.
>
> After each render (except during interaction), the view automatically takes
> a "snapshot" of what is currently rendered in a special render mode that
> maps pixel locations particular actors and cells. When the user's mouse
> stops over a cell, the render view looks up the hovered cell in the map and
> sends it to its representations to possibly produce a hover label.
> Representations manage the pipleline/mappers/actors for displaying a
> particular type of data in a view. They implement support for hover queries
> by overriding GetHoverTextInternal().
>
> This is currently implemented in vtkRenderedGraphRepresentation, where the
> user may select the vertex and edge hover arrays.
>
> The view also allows the hover labels not to be rendered with OpenGL, but
> invokes a HoverEvent when the hover label changes. This would allow an
> application to capture these events and use real native tooltips (e.g. with
> Qt) to show the hover labels.
>
> Jeff
>
>
>
>
>    ****      Kenneth Moreland
>     ***      Sandia National Laboratories
> ***********
> *** *** ***  email: kmorel at sandia.gov
> **  ***  **  phone: (505) 844-8919
>     ***      web:   http://www.cs.unm.edu/~kmorel
>
>
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