[vtkusers] Force rendering from a thread
totte at dunescientific.com
Tue Jan 13 20:38:46 EST 2015
On 1/13/2015 4:36 PM, David Gobbi wrote:
> The rendering in VTK must be done from the main application thread
> (i.e. the thread that runs the application's main event loop), and in
> an application, polling is an excellent way for the main loop to check
> if any other threads require attention. So my advice is that you
> become a fan of polling. In this case, it's the right way forward.
I see. Currently I have a very simple polling timer, checking for an
integer being set to 1 or 0. If the integer is set, I do a render. Works
fine. Don't need a mutex for that I assume.
> You could, instead, have your thread ask the operating system to send
> your application some kind of notification that the main loop could
> respond to, but that would probably be less efficient than polling
> (and it would be platform-specific). Or, in Qt, you could take
> advantage of an asynchronous signal-slot connection and let Qt take
> care of the details (Qt would either do polling internally, or would
> use an OS-level notification, I'm not sure which).
I'm not familiar with Qt slots, and I have not tried the polling in a ms
windows application yet. But I guess one can post a custom user message,
that is intercepted in the apps message loop (which is polling), and
handle it there. Would just be a call to render();
Obviously I take your word for becoming a fan of polling! Thanks.
> I have noticed when I execute renderInteractive(), that vtk
> objects are indeed updated from their sources every time the mouse
> interactively generate a 'render' somewhere. Not sure how that
> works. Is it possible to tie in there somewhere?
> The mouse events are caught by the application's main loop, and the
> main application thread responds to these events (and performs the
> render at the end). So you won't find any insight there about how to
> do things in a multi-threaded fashion.
I assume it is so that the renderInteractive() call creates the
"application loop", in a console application, since there is only one
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