How to reduce CPU uages with Opengl ?

[GAJERA]

Hi All I am using gluBuild2DMipmaps() for show live video buffer. but it is using the CPU around 50%. Please suggest how to reduce CPU usages. Here I am sending you the source code for render.

for (int loop=0; loop<2; loop++) // Loop To Draw Our 4 Views
{
if (loop==0) // If We Are Drawing The First Scene
{
m_bRenderFromVideo=FALSE;
if(m_pbVideoData)
gluBuild2DMipmaps(GL_TEXTURE_2D, 3, m_iVideoHeight,m_iVideoWidth ,GL_LUMINANCE, GL_UNSIGNED_BYTE, m_pbVideoData);

		glViewport(m\_iNoOfColumn - m\_iNoOfColumn \* m\_iSizeVideo.x, m\_iNoOfRow - m\_iNoOfRow \* m\_iSizeVideo.y, 
		m\_iNoOfColumn \* m\_iSizeVideo.x, m\_iNoOfRow \* m\_iSizeVideo.y);
		glPushMatrix();

		gluOrtho2D(-window\_width/4, window\_width/4, -window\_height/4, window\_height/4);
		//glDrawPixels( window\_width/2,  window\_height/2, GL\_LUMINANCE,GL\_UNSIGNED\_BYTE, (void\*)m\_pbVideoData);
		glLoadIdentity ();											// Reset The Projection Matrix

		glDisable(GL\_TEXTURE\_GEN\_S);								// Enable Texture Coord Generation For S (NEW)
		glDisable(GL\_TEXTURE\_GEN\_T);								// Enable Texture Coord Generation For T (NEW)

		glDisable(GL\_LIGHTING);
		glBegin(GL\_QUADS);											// Begin Drawing A Single Quad
		// We Fill The Entire 1/4 Section With A Single Textured Quad.
	
		glTexCoord2f(1.0f, 1.0f); glVertex3f( 21.0f,  18.3f, -10.0f);
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-21.0f,  18.3f, -10.0f);
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-21.0f, -18.3f, -10.0f);
		glTexCoord2f(1.0f, 0.0f); glVertex3f( 21.0f, -18.3f, -10.0f);
		glEnd();	

		glScalef(m\_fScale, m\_fScale, m\_fScale);
		glRotated(m\_fRAngle\[0\],0.0, 0.0,1.0);
		//glRotated(0,0.0,0.0, m\_fRAngle\[0\]);
		//glRotated(0,0.0,0.0,m\_fRAngle\[0\]);	   

		
	}
	else		
	{
		glPushMatrix();
		glViewport(0, 0, window\_width, window\_height);
		//float len = 28.0f;			
		//glMatrixMode(GL\_PROJECTION);
		glLoadIdentity();
	//	glOrtho(-len, len, -len, len, -len\*100.0f, len\*100.0f);	
	//	glMatrixMode(GL\_MODELVIEW);

		glScalef(m\_fScale, m\_fScale, m\_fScale);
		glRotated(m\_fRAngle\[0\],1.0, 0.0, 0.0);
		glRotated(m\_fRAngle\[1\],0.0,1.0, 0.0);
		glRotated(m\_fRAngle\[2\],0.0,0.0,1.0);	   


	}
	
	
}

[Emilio Garavaglia]

You have two choiches: 1) Buy a computer with a faster CPU 2) Check if the OpenGL settings on your computer are fine with your hardware (that may be OpenGL capable itself, but may be the library doesn't know it) Seriously: there is nothing strange in your program. Simply, OGL is a bad beast! The only thing to check is the driver of your graphic card (are they the correct ones? sometime the OS setups guess wrong settings) and relative settings (if they are), as well as the OGL settings in the control panel (if there are).

2 bugs found. > recompile ... 65534 bugs found. :doh:

[Cedric Moonen]

GAJERA wrote:

but it is using the CPU around 50%.

How does your main loop looks like ? I am guessing that you have a continuous loop without any sleep and that your program runs on a double core. In that case what happens is that your loop will be executed continuously and you will probably get a very high framerate. If you can live with a lower (and fixed) framerate, you can simply execute your drawing code every x msec (choose an appropriate time interval between two frames). The rest of the time, your program should sleep (well in fact wait for user events). You can find more info in one of my articles here[^]

Cédric Moonen Software developer
Charting control [v3.0] OpenGL game tutorial in C++