how does gluunproject work?

OpenGL Development
#1

how do i use guunproject? and is there any way to change an x-y position with a specified depth on the screen to an x-y-z position within opengl?

#2

That’s how I do it .
your Z will be got based on your depth Buffer .


	  static IntBuffer viewport = BufferUtils.createIntBuffer(16);
	  static FloatBuffer modelview = BufferUtils.createFloatBuffer(16);
	  static FloatBuffer projection = BufferUtils.createFloatBuffer(16);
	  static FloatBuffer winZ = BufferUtils.createFloatBuffer(1);
	  static FloatBuffer position = BufferUtils.createFloatBuffer(3);

       /* PomVertice is just a class with float x,y,z  coordinates */
        static public PomVertice getMousePosition(int mouseX, int mouseY)
	{

	viewport.clear();
	modelview.clear();
	projection.clear();
	winZ.clear();;
	position.clear();
	float winX, winY;


	GL11.glGetFloat( GL11.GL_MODELVIEW_MATRIX, modelview );
	GL11.glGetFloat( GL11.GL_PROJECTION_MATRIX, projection );
	GL11.glGetInteger( GL11.GL_VIEWPORT, viewport );

	winX = (float)mouseX;
	winY = //(float)viewport.get(3) -// 	(float)mouseY; /* it depends on how you're treating you Y axis */

	GL11.glReadPixels(mouseX, (int)winY, 1, 1, GL11.GL_DEPTH_COMPONENT, GL11.GL_FLOAT, winZ);

	float zz = winZ.get();
	GLU.gluUnProject(winX, winY, zz, modelview, projection, viewport, position);
	PomVertice v = new PomVertice(position.get(0),position.get(1),position.get(2));
	return v ;
	}
#3

OK i get it. if i use a distance from the camera say, from my mouse wheel, it would tell me where to draw my pointer in 3d space

#4

P.S how would i get a rendered cursor to always face me? point sprites?