Quick Selection Question

[Richard145]

Please Help,

I am new to the OpenGL Selection and have a quick question that I hope someone can help me with. I get the selection to work fine, i.e., I can record "hits" when switching from GL_SELECT to GL_RENDER but the NAME is not stored.

The output I get (when I select the Object):
"--------------------------
HITS: 1
- - - - - - - - - - - - - -
Number of Names: 0
z1: -0.09484
z2: -0.3213
names:
- - - - - - - - - - - - - - -
------------------------------"

The following is the code from which the previous console output comes:

private void processHits(int hits, IntBuffer buffer) {
        	System.out.println("---------------------------------");
        	System.out.println(" HITS: " + hits);
        	int offset = 0;
        	int names;
        	float z1, z2;
        	for (int i = 0; i < hits; i++) {
            		System.out.println("- - - - - - - - - - - -");
            		System.out.println(" hit: " + (i + 1));
            		names = buffer.get(offset);
            		offset++;
            		z1 = (float) buffer.get(offset)/0x7fffffff;
            		offset++;
            		z2 = (float) buffer.get(offset)/0x7fffffff;
            		offset++;
            		System.out.println(" number of names: " + names);
            		System.out.println(" z1: " + z1);
            		System.out.println(" z2: " + z2);
            		System.out.println(" names: ");
 
            		for (int j = 0; j < names; j++) {
                		System.out.print("  " + buffer.get(offset));
                		if (j == (names - 1)) {
                    			System.out.println("<-");
                		}else {
                    			System.out.println();
                		}
                		offset++;
            		}// End of INNER FOR-LOOP
            		System.out.println("- - - - - - - - - - - -");
        	}// End of OUTER FOR-LOOP
        	System.out.println("--------------------------------- ");
    	}// End of processHits(int,IntBuffer)

The naming of the Object is done in the following code:

  int[] viewport = new int[4];
        	int hits = 0;
 
		// allocate fast memory. Necessary since glSelectBuffer takes IntBuffer	
		//
		ByteBuffer byteBuffer = ByteBuffer.allocateDirect(4*BUFFERSIZE);
        	byteBuffer.order(ByteOrder.nativeOrder());
        	this.selectionBuffer = byteBuffer.asIntBuffer();
 
		// Get the current Viewport for this Class
		//
        	this.gl.glGetIntegerv(GL.GL_VIEWPORT, viewport, 0);
 
        	// the hits will be stored in the selection buffer after.
		//
        	// Note that it's called *before* we change the render mode
		//
        	this.gl.glSelectBuffer(selectionBuffer.capacity(), this.selectionBuffer);
 
		// Set the GL Rendering Mode to SELECT
		//
        	this.gl.glRenderMode(GL.GL_SELECT);
 
		// clear name stack
		//
        	this.gl.glInitNames();                      
 
		// Switch to the Projection Matrix
		//
        	this.gl.glMatrixMode(GL.GL_PROJECTION);
 
		// save current projection matrix
		//
        	this.gl.glPushMatrix();
 
        	// reset the projection matrix
		//
        	this.gl.glLoadIdentity();                    
 
		// restrict drawing to around the cursor
		//
        	this.glu.gluPickMatrix(this.mouseX, viewport[3] - this.mouseY, 5.0d, 5.0d, viewport, 0);
this.glu.gluPerspective(45, this.ratio, 1, 200);
this.gl.glMatrixMode(GL.GL_MODELVIEW);
if (mode == GL.GL_SELECT) {
				gl.glPushName(20);
			}
// Call draw() that is using geometric primatives to render Object
draw();
 
this.gl.glMatrixMode(GL.GL_PROJECTION);
this.gl.glPopMatrix();
hits = gl.glRenderMode(GL.GL_RENDER);
this.mode = GL.GL_RENDER;
processHits(hits, selectionBuffer);

Thanks be to anyone that has any idea why this is happening.

[Ido Ilan]

Hi,

Where is the glPopName?

Ido

[Richard145]

Oops. I think I got the call mixed up with glLoadName()?

[Richard145]

Still no luck. I tried using both glLoadName(GLUint) and (when that didn't work) I instead did the glPushName(GLUint) (draw Object with primatives) followed by glPopName().

Perhaps it is my printing out function?

[Richard145]

Never mind. I found it. I was not setting GL_SELECT when drawing the Model at all so the name stack was never loaded.

The result of a long day of coding with no breaks.