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2D mouse mapping

Started by dnaxx Apr 12, 2006 at 1:21 PM 2 replies 450+ views

Original Post

Apr 12, 2006 at 1:21 PM

Hello! I am using GLUT (and it's mouse callback functions) and now I want to map the coordinates from mouse clicks to world coordinates. This must only be done in 2D (the clicks are used for 2D controlls like checkboxes and buttons). How can I do this mapping? thank you,

dnaxx

Author

dnaxx

Apr 12, 2006 at 1:42 PM

	printf("Mouse x: %i, y: %i\n",x,y);	GLint viewport[4];	GLdouble mvmatrix[16], projmatrix[16];	GLint realy;	GLdouble wx,wy,wz;		glGetIntegerv(GL_VIEWPORT,viewport);	glGetDoublev(GL_MODELVIEW_MATRIX,mvmatrix);	glGetDoublev(GL_PROJECTION_MATRIX,projmatrix);	realy = viewport[3] - (GLint) y - 1;	gluUnProject((GLdouble)x, (GLdouble) realy, 0.0, mvmatrix,projmatrix,viewport,&wx,&wy,&wz);	printf("World x: %f, y: %f\n",wx,wy);

I used this code from the Red Book and it return reasonable results for 3D scenes. But for my 2D elements hte world x,y values are "strange" (x ~= 0-1, y ~= 4-5).

Here is also the code after which 2D elements are drawn:

			glMatrixMode(GL_PROJECTION);			glPushMatrix();							glLoadIdentity();						gluOrtho2D (0, 800, 0, 600);			//gluOrtho2D (0, 800, 0, 600);			glMatrixMode(GL_MODELVIEW);				// Draw 2D elements here

dnaxx

Author

dnaxx

Apr 12, 2006 at 2:10 PM

Just another question: Are the OpenGL picking functions ("glSelectBuffer()"...) "good"?

Fahrenheit451

Apr 12, 2006 at 2:46 PM

I answered the question of mouse coordinate conversion quite recently in this thread. See if that helps any. You have the general idea though. The oddity might be the orientation of your viewport not being taken into consideration in the conversion calcs - (0,0) being lower left or top left.

F451

[Edited by - Fahrenheit451 on April 12, 2006 4:46:46 PM]

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