Setting up Rendering In a Separate Thread.

[thecurseofnor]

Hello. I'm experiencing some lag during my program's event loop when I move the mouse. So I was hoping to someone could direct me to a method for separating the event loop from the rendering code with a separate thread.

[Laurent]

This shouldn't happen. How many mouse events do you receive per frame?

[thecurseofnor]

sf::Event::MouseMoved occurs  about 4-6 times a frame, If thats what you meant. Its a small lag. Hardly
noticeable, yet still noticeable. From what I've seen, the more events I check for in the event loop, whatever they may be, the more sf::Event::MouseMoved events I get. Is it something I'm doing wrong?

[Laurent]

And what do you do when you receive these events?

[thecurseofnor]

example:

Code: [Select]

if((event.type == sf::Event::MouseButtonPressed) && (event.mouseButton.button == sf::Mouse::Left))
myclass.doThis = true;
I should also mention, I'm using SFML 2.0 RC.
And I didn't experience this in SFML 1.6.

But besides this, I'd still like to know how to set up a separate Render Thread.

[thecurseofnor]

Well I've been reworking my event loop. And I've managed to reduce the amount of necessary event checks to a much smaller amount. And now the mouse move lag is undetectable. Though I'm still open to methods of setting up the rendering code in a separate thread. Currently the program crashes whenever I attempt it.

[Laurent]

Currently the program crashes whenever I attempt it

Can you show what you tried?

[thecurseofnor]

This is what I tried putting into a thread;

void Render(void * data)
{
        sf::RenderWindow &window = *(static_cast<sf::RenderWindow*>(data));
       
        while(window.isDone())
        {
                // Render 3D
                glLoadIdentity();
                glTranslatef( 0, 0, -5 );

                glBegin(GL_QUADS);
                          glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f, -1.0f, 1.0f );
                          glTexCoord2f( 1.0f, 1.0f ); glVertex3f(  1.0f, -1.0f, 1.0f );
                          glTexCoord2f( 1.0f, 0.0f ); glVertex3f(  1.0f,  1.0f, 1.0f );
                          glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f,  1.0f, 1.0f );

                          glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, -1.0f, -1.0f );
                          glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f,  1.0f, -1.0f );
                          glTexCoord2f( 1.0f, 1.0f ); glVertex3f(  1.0f,  1.0f, -1.0f );
                          glTexCoord2f( 1.0f, 0.0f ); glVertex3f(  1.0f, -1.0f, -1.0f );

                          glTexCoord2f( 1.0f, 1.0f ); glVertex3f( -1.0f,  1.0f, -1.0f );
                          glTexCoord2f( 1.0f, 0.0f ); glVertex3f( -1.0f,  1.0f,  1.0f );
                          glTexCoord2f( 0.0f, 0.0f ); glVertex3f(  1.0f,  1.0f,  1.0f );
                          glTexCoord2f( 0.0f, 1.0f ); glVertex3f(  1.0f,  1.0f, -1.0f );

                          glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f, -1.0f, -1.0f );
                          glTexCoord2f( 1.0f, 1.0f ); glVertex3f(  1.0f, -1.0f, -1.0f );
                          glTexCoord2f( 1.0f, 0.0f ); glVertex3f(  1.0f, -1.0f,  1.0f );
                          glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, -1.0f,  1.0f );

                          glTexCoord2f( 0.0f, 0.0f ); glVertex3f( 1.0f, -1.0f, -1.0f );
                          glTexCoord2f( 0.0f, 1.0f ); glVertex3f( 1.0f,  1.0f, -1.0f );
                          glTexCoord2f( 1.0f, 1.0f ); glVertex3f( 1.0f,  1.0f,  1.0f );
                          glTexCoord2f( 1.0f, 0.0f ); glVertex3f( 1.0f, -1.0f,  1.0f );

                          glTexCoord2f( 1.0f, 0.0f ); glVertex3f( -1.0f, -1.0f, -1.0f );
                          glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, -1.0f,  1.0f );
                          glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f,  1.0f,  1.0f );
                          glTexCoord2f( 1.0f, 1.0f ); glVertex3f( -1.0f,  1.0f, -1.0f );
                        glEnd( );

                glLoadIdentity();


               
                window.display();
                glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
                glMatrixMode(GL_MODELVIEW);
                glLoadIdentity();
        }
}

And the program crashed with the output:

[xcb] Unknown sequence number while processing queue
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
rthread: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
Aborted

[Laurent]

Yep, XInitThreads (Linux only) must be called for multithreading to work. This will be fixed soon.

And you must deactivate the window in its initial thread (window.setActive(false)) before activating it in its new thread (window.setActive(true)).

[Ceylo]

What is sf::RenderWindow::isDone() ? First time I see this and I can't find it in the documentation of sf::RenderWindow.

[Laurent]

Probably isOpen().