Sparrow Forum

1. 

   synergie7
   Member

   I have an app where I take a snapshot of the screen.
   The snapshot code is working fine, but I'm not sure when screen rendering is complete, so that I can trigger the snapshot to be taken.

   i.e I have a complex scene with multiple objects, with sub objects.
   The scene builder, adds all the objects (image etc), and as soon as this code completes, I trigger an event. The event handler code, then takes a snapshot.

   However if I take the snapshot straight away. The snapshot is blank.
   But if I wait 2 frames, the snapshot works.

   Is waiting a couple of frames a reliable way to do this, or should I really be using something else i.e some other event?

   Edit.

   Since first posting, I've tried using the ADDED_TO_STAGE event, but this doesn't seem to fix it. i.e I can't take a snapshot straight after that event has been recieved

   Perhaps I should wait for that event, then wait another few frames??

   Posted 3 months ago #
2. 

   Jugibur
   Moderator

   There is not a special event for this, but as I know, after the first rendering all objects are drawn to the screen. There is no "half" rendering, because while building the display tree the rendering cycle isn't step further.
   So it seems after "onAddedToStage" the objects aren't rendered at this point.

   But I'm not an OpenGL expert, just my thoughts after using Sparrow for a while.

   Posted 3 months ago #
3. 

   synergie7
   Member

   Thanks Jugibur

   At the moment the only way I can get it to work reliably is to wait for ADDED_TO_STAGE then wait about 10 x ENTER_FRAME events to occur.

   Ideally, I need to render just one display object to a UIImage which I then save as a screen snapshot, but I only want to render the playing area and not the controls etc.

   I took a look in the core of Sparrow to see how the stage is rendered, and have done some research and it appears to be possible to create an off screen buffer and that openGL can draw to that buffer.

   So when I get time, I need to try to write code to do off screen rendering, of a display object / display object container.
   But at the moment I don't know anything about OpenGL, so I'll need to do a lot of reading, and hope I can find an example of doing off screen rendering using OpenGL

   I'll re-post if I make any progress

   Cheers

   Roger

   Posted 3 months ago #

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