Backbuffer as Texture

OpenGL OpenGL: Basic Coding
1

hi,

im trying to draw something on my backbuffer, save it as a texture, and then put the texture in a simple plane. here is the snipplet of my code:


void display() {
	
	glClearColor(1.0, 1.0, 1.0, 0);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	
	glPushAttrib(GL_COLOR_BUFFER_BIT | GL_PIXEL_MODE_BIT);
	glDrawBuffer(GL_BACK);
	glReadBuffer(GL_BACK);
	
	drawOrbit();
	
	glBindTexture(GL_TEXTURE_2D, img);
	glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, width, height);
	glBindTexture(GL_TEXTURE_2D, 0);
	
	glPopAttrib(); 
	
	
	glClearColor(1.0, 1.0, 1.0, 0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
	
	glLoadIdentity();
	
	//glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
	
	glTranslatef(0, 0, -1.5f);
	glTranslatef(0, 0, -zoom);
	
	glBindTexture(GL_TEXTURE_2D, img);
	glBegin(GL_QUADS);
	{
		glNormal3f(0.0, 0.0, 1.0);
		glTexCoord2f(1, 1);  glVertex3f(1,1,0);
        glTexCoord2f(0, 1);  glVertex3f(-1,1,0);
        glTexCoord2f(0, 0);  glVertex3f(-1,-1,0);
        glTexCoord2f(1, 0);  glVertex3f(1,-1,0);
	}
	glEnd();
	glBindTexture(GL_TEXTURE_2D, 0);
	//glFlush();
	glutSwapBuffers();
}

the drawOrbit() method is simply drawing to the screen and works properly. however i can see the result on my screen. it simply draw the plane with default color. i use variable img as my texture ide, here is when i set my texture:


glGenTextures(1, &img);
	glBindTexture(GL_TEXTURE_2D, img);
	glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );
	
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_NEAREST );
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
	glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,GL_REPEAT);
    glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,GL_REPEAT);
	glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
	
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, 
				 GL_UNSIGNED_BYTE, NULL);
	glBindTexture(GL_TEXTURE_2D, 0);

did i miss anything? how can i make it works?

thanks in advance

2

Before drawing your textured plane you need to enable texturing:


glEnable(GL_TEXTURE_2D);