[eq-dev] Getting the Field-of-view for a particular segment when rendering?
cpapado
segment (I am doing some LoD related stuff that require this).
Is there some way to get to this info from inside eq::Channel::frameDraw()
(or at least get access to the current Wall and Segment geometries so i can
calculate it manually for a given viewer position)?
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Stefan Eilemann
On 24. Jan 2012, at 2:24, cpapado [via Software] wrote:
> My application requires the per-segment FoV when rendering the contents of a segment (I am doing some LoD related stuff that require this).
>
> Is there some way to get to this info from inside eq::Channel::frameDraw() (or at least get access to the current Wall and Segment geometries so i can calculate it manually for a given viewer position)?
You can't, by design, get to the wall/segment stuff from the render clients.
When you need the FOV there is often a deeper underlying problem: Getting the FOV of a segment is not enough, since the same image might be generated by multiple segments or a big, single display. Getting the FOV of a canvas does not work for non-planar surfaces. The FOV might change through the view's wall description. Tracking is another variable.
What you often want for LOD is the screen-space coverage of your geometry in pixels or centimeters as an input parameter. This you can compute without having access to the segment/canvas.
That said, I strongly advise to look at your LOD code. If you really want to go the FOV route, '1 / vp.w * pixel.w' should give you the theoretical fraction of the destination canvas covered by your channel, the frustum gives you the sub-FOV.
HTH,
Stefan.
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