8:00 – FP

• Chasing down why the refresh rate drops after using glGetQueryObjectiv(drawQuery, GL_QUERY_RESULT, &result);
• Adding a check to test that the result is available before pulling it.
• Changed the code so that the hit test is only called once per mouse click. Not sure why that would fix it, but I’m not complaining.
• Cleaned up and working. Example code for how to do non-fixed pipeline picking in OpenGL shown below:

// Code to show how to use object queries to get picking behavior. For this code to work,
// You'll need to add your preferred rendering framework. This code was pulled from an
// FLTK framework I've been building for data visualization

// Class-wide global variables here for the sake of a compact file
// Classes that are not part of the OpenGl library are from the OpenGl SuperBible,
// which I highly reccomend: http://www.starstonesoftware.com/OpenGL/

GLMatrixStack modelViewMatrix;
GLMatrixStack projectionMatrix;
GLFrustum viewFrustum;
bool isPicking;

// Constructor. Set up picking and the projection and model matrices
PickingExample::PickingExample(int x,int y,int w,int h,const char *l)
: Fl_Gl_Window(x,y,w,h,l)
{
	isPicking = false;
	pickQueryResult = READY;
	glGenQueries(1, &pickQueryID);
	if(pickQueryID == 0){
		pickQueryResult = PICK_ERROR;
	}

	viewFrustum.SetPerspective(45.0f, (float)screenWidth/(float)screenHeight, 0.5f, 1000.0f);
	projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
	modelViewMatrix.LoadIdentity();
}

// A slightly modified version of the original gluPickMatrix, taken from:
// http://oss.sgi.com/cgi-bin/cvsweb.cgi/projects/ogl-sample/main/gfx/lib/glu/libutil/project.c?rev=1.4;content-type=text%2Fplain
void PickingExample::setPickMatrix(GLdouble x, GLdouble y, GLdouble deltax, GLdouble deltay, GLint viewport[4])
{
	if (deltax <= 0 || deltay <= 0) {
		return;
	}

	projectionMatrix.LoadIdentity();

	/* Translate and scale the picked region to the entire window */
	GLfloat dx = (float)((viewport[2] - 2 * (x - viewport[0])) / deltax);
	GLfloat dy = (float)((viewport[3] - 2 * (y - viewport[1])) / deltay);
	projectionMatrix.Translate(dx, dy, 0);
	projectionMatrix.Scale((float)(viewport[2] / deltax), (float)(viewport[3] / deltay), 1.0);

	projectionMatrix.MultMatrix(viewFrustum.GetProjectionMatrix());
}

// the main drawing method. In this case, only drawing for picking is done, though it would 
// be easy enough to glClear() afther the picking code, and draw everything  over again with 
// a normal perspective
void PickingExample::draw() {
	GLint result;
	GLint viewport[4];
	glGetIntegerv(GL_VIEWPORT,viewport);

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	modelViewMatrix.PushMatrix();

		// Have some Euler angle rotations and translations just to show how
		// setPickMatrix() doesn't care about eye or model position

		// global eye transformations
		modelViewMatrix.Rotate(eyeOrient[1], 0, 1, 0);
		modelViewMatrix.Rotate(eyeOrient[0], 1, 0, 0);
		modelViewMatrix.Translate(eyePos[0], eyePos[1], eyePos[2]);

		// global world transformations
		modelViewMatrix.Translate(worldPos[0], worldPos[1], worldPos[2]);
		modelViewMatrix.Rotate(worldOrient[0], 1, 0, 0);
		modelViewMatrix.Rotate(worldOrient[1], 0, 1, 0);

		// set up picking
		if(isPicking && (pickQueryResult != PICK_ERROR))
			projectionMatrix.PushMatrix();
				// set the projection matrix so that it's just looking at a (in this case) 10x10 pixel area
				// near the cursor. This method (shown above)
				setPickMatrix(mouseX,viewport[3]-mouseY,10,10,viewport);

				// for each item that you want to test, bracket it with a glBeginQuery()/glEndQuery()
				// You'll need a unique pickQueryID for each model
				glBeginQuery(GL_ANY_SAMPLES_PASSED, pickQueryID);

					// render your model associated with pickQueryID here. It is assumed that
					// the projection matrix and the model matrix will be handled by your shader(s)

				// finish the query for this particular model
				glEndQuery(GL_ANY_SAMPLES_PASSED);

			projectionMatrix.PopMatrix();

			// For each item that you queried above, see if at least one pixel was drawn
			// Again, you'll need a unique pickQueryID for each model
			glGetQueryObjectiv(pickQueryID, GL_QUERY_RESULT, &result);
			if(result)
				printf("hitn");
			else
				printf("missn");

			isPicking = false;
		}
	modelViewMatrix.PopMatrix();
}