[Interest] Qt3D - QObjectPicker & back-face culled entities

[Philip Schuchardt]

It doesn't appear to be supported in the current documentation (5.7).
Another way to solve this is by rendering each object with a unique picking
color and the querying the pixel color under the mouse.  This could
probably be done by setting up a framegraph and use a RenderCapture
(although, I haven't gotten a RenderCapture to work).  With this
method, back-face culled entities will be handled correctly. One downside
to this method is that you'll only be able to query the closest pixel. I
guess you could do something like depth peeling to get other pixels, but
seem a bit extreme. With the pixel-based approach, you can improve
performance by reducing the size of the viewport. Reducing the size trades
off accuracy for performance by the way. For example squishing a 1000 x
1000 pixel viewport into 10 x 10 pixel viewport would give you good raster
performance but your picking wouldn't be very accurate.

Perhaps adding a flag to QPickerSetting to support back-face culling would
be a nice feature. Have you looked in Qt bug tracker?

Also, is the triangle picking is accelerated in any way? Or does the
algorithm just brute force through all the triangles?

On Wed, Dec 7, 2016 at 12:41 AM Andy <asmaloney at gmail.com> wrote:

> (Since I didn't get any response from my last question about picking I
> thought I'd try asking it in a different way.)
>
> How do I prevent the object picking mechanism from "seeing" back-face
> culled entities so that it picks entities based on what the user is
> actually seeing in the scene?
>
> Thank you!
>
> ---
> Andy Maloney  //  https://asmaloney.com
> twitter ~ @asmaloney <https://twitter.com/asmaloney>
>
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-- 
Phi|ip
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