QGraphicsView animation performance

[rakkar]

I want to display an animated image with QGraphicsView. The animated image will play at 30 frames per second, and I will have multiple images at the same time. One way to do it is to have a list of QGraphicsPixmapItem, and keep feeding that to QGraphicsScene. But that seems inefficient. Is there any better way to do this that I'm missing? Maybe I should access the OpenGL device directly?

[wysota]

If your viewport is OpenGL based then you can use OpenGL calls to render your item.

[rakkar]

All I'm trying to do is render a triangle and a square (from here http://nehe.gamedev.net/data/lessons....asp?lesson=02 ) , but the viewport is always black.

VisualizationWindowClass is just a blank dialog from QtDesigner

class VisualizationWindow : public VisualizationWindowClass, public QGLWidget
{
virtual void initializeGL(){
	qglClearColor(Qt::black);
	glShadeModel(GL_FLAT);
}
	virtual void resizeGL( int w, int h ){
	glViewport( 0, 0, (GLint)w, (GLint)h );
}
	virtual void paintGL(){
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();
	glTranslatef(-1.5f,0.0f,-6.0f);
	glBegin(GL_TRIANGLES);						// Drawing Using Triangles
	glVertex3f( 0.0f, 1.0f, 0.0f);				// Top
	glVertex3f(-1.0f,-1.0f, 0.0f);				// Bottom Left
	glVertex3f( 1.0f,-1.0f, 0.0f);				// Bottom Right
	glEnd();		
	glTranslatef(3.0f,0.0f,0.0f);
	glBegin(GL_QUADS);						// Draw A Quad
	glVertex3f(-1.0f, 1.0f, 0.0f);				// Top Left
	glVertex3f( 1.0f, 1.0f, 0.0f);				// Top Right
	glVertex3f( 1.0f,-1.0f, 0.0f);				// Bottom Right
	glVertex3f(-1.0f,-1.0f, 0.0f);				// Bottom Left
	glEnd();							// Done Drawing The Quad
 
}
 
}

class VisualizationWindow : public VisualizationWindowClass, public QGLWidget
{
virtual void initializeGL(){
	qglClearColor(Qt::black);
	glShadeModel(GL_FLAT);
}
	virtual void resizeGL( int w, int h ){
	glViewport( 0, 0, (GLint)w, (GLint)h );
}
	virtual void paintGL(){
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();
	glTranslatef(-1.5f,0.0f,-6.0f);
	glBegin(GL_TRIANGLES);						// Drawing Using Triangles
	glVertex3f( 0.0f, 1.0f, 0.0f);				// Top
	glVertex3f(-1.0f,-1.0f, 0.0f);				// Bottom Left
	glVertex3f( 1.0f,-1.0f, 0.0f);				// Bottom Right
	glEnd();		
	glTranslatef(3.0f,0.0f,0.0f);
	glBegin(GL_QUADS);						// Draw A Quad
	glVertex3f(-1.0f, 1.0f, 0.0f);				// Top Left
	glVertex3f( 1.0f, 1.0f, 0.0f);				// Top Right
	glVertex3f( 1.0f,-1.0f, 0.0f);				// Bottom Right
	glVertex3f(-1.0f,-1.0f, 0.0f);				// Bottom Left
	glEnd();							// Done Drawing The Quad

}

}

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[wysota]

So are you using Graphics View or not?

[rakkar]

It doesn't seem to be necessary. The system can just display a QGLWidget. If I change the clear color it displays a different color for example. It just doesn't draw anything else.

[wysota]

If all you want is a triangle and a square, I'd use QPainter instead of pure OpenGL calls. You can render on QGLWidget if you want of course...

[rakkar]

If all you want is a triangle and a square, I'd use QPainter instead of pure OpenGL calls. You can render on QGLWidget if you want of course...

Thanks but that's not what I want. I'm just demonstrating that even the simplest case doesn't work.

[wysota]

It doesn't work probably because your viewport is setup incorrectly. Go to link you provided, scroll down and download the sources fot C++/Qt. You'll see they set up the modelview matrix too.

[rakkar]

It doesn't work probably because your viewport is setup incorrectly. Go to link you provided, scroll down and download the sources fot C++/Qt. You'll see they set up the modelview matrix too.

Fantastic, thanks for pointing that out.