confusing problem !!!

[glcrazy]

Hi everybody ...

I'm trying to dragg a rectangle in a condition that tha mouse pointer is inside that rectangle ..

I drew the rectangle using
glRectf(px1,py1,px2,py2)..

the coordinates of the rectangle are (0,-65,20,-70);

The problem that when I click INSIDE the rectangle and get back the value of x & y using the glutMouse function , I found that the values of x & y CAN'T be inside the rectangle ( something like 209, 361 ) eventhough I was pressing inside that rectangle !!!!!

Any body can inlighten Me .. !

Thanks in Advance

[glcrazy]

Here is an explanation draw :

[mikael_aronsson]

Hi !

Mouse coordinates have nothing to do with the coordinates of the rectangle, on most platforms the mouse coordinates has their origin in the upper left corner and maps 1:1 to the device resolution.

The rectangle coordinates depends on your modeview matrix setup, if you do want to map them to mouse coordinates have a peek at the faq on this website (transformations section), there is an example on how to setup the modelview matrix to match the device resolution (with a flipped Y axis).

Mikael

[glcrazy]

Thanks Mikael for your quick responce ..

I'm really not familiar on what you have said a bout mapping the modelview to match the device resolution eventhough I will look in the transformations section ..

I wonder if there is other method to make sure that the mouse click is inside the rectangle .. ??

Cheers,

[virtualchetan]

Hello,

I think ur problem is that u r not converting the mouse coordinates from window co-ordinate system to rectangle coordinate system.

Based on the code u posted for the previous problem, I think ur doing lots of projection and modelview transformations, and then render the rectangle, so u have to take care of those for mouse co-oridnates also.

- Chetan

[glcrazy]

Originally posted by virtualchetan:
I think ur problem is that u r not converting the mouse coordinates from window co-ordinate system to rectangle coordinate system.
- Chetan

Hello Chetan ..

How can I do that .. I.e, convert the mouse coordinate from window to rectangle coordinate system ???

I tried to apply the projection and modelview transformations I did to glut mouse function and I get no result I mean there is still big different between the two system coordinate ..

Thank you for your explanation & support Chetan ..

[nexusone]

The mouse function returns the value in pixels, not openGL world units.

Lets say you have a openGL world of -10,-10 to 10,10, you viewport is 200 x 200 pixels.

This converts windows pixels to openGL world values.

Where x/y is mouse values and Win_x/y are hight and width of window in pixels.

// my mouse routine
void mouse(int button, int state, int x, int y)
{

Mouse_x = -10 + 20 * (x/Win_x);
Mouse_y = 10 - 20 * (y/Win_y);

// Mouse_x/y tells us where in openGL units the mouse was clicked.

}

// My reshape routine
void reshape_1 (int w, int h)
{
Win_x = w; // Get new value of windows witdh when window size change
Win_y = h; // Get new value of hight
glViewport (0, 0, (GLsizei) w, (GLsizei) h); // Tell openGL the new window size
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
}


[This message has been edited by nexusone (edited 12-02-2003).]

[glcrazy]

Hello nexusone,

I was trying your code all that time but I fave up .. it didn't work .. now it gives me a fixed value for x & y !!!

Here is my mouse function :
void myGlutMouse(int button, int button_state, int x, int y )
{
switch(button)
{
case GLUT_RIGHT_BUTTON:
{
if ((button_state == GLUT_DOWN))
{
x = -80 + 160 *(x / Winx);
y = 80 + 160 *(x / Winy);
// if ((x>= (pX1+290)) && (x<=(pX1+pX2+361)) && (y>= 535) && (y<= 552) )
// {
dragging = true ;
last_x = x;
last_y = y;
// }
}
else
dragging = false ;
}
}
}

Here is my reshape function :
void myGlutReshape( int x, int y )
{
int tx, ty, tw, th;
Winx= tw;
Winy= th;

GLUI_Master.get_viewport_area( &tx, &ty, &tw, &th );
glViewport( tx, ty, tw, th );

// xy_aspect = (float)tw / (float)th;

glutPostRedisplay();
}


I beleived my world is between ( -80,-80, 80,80) and my viewport is 600 × 600 .


Thank you in advance


[This message has been edited by glcrazy (edited 12-04-2003).]

[nexusone]

The problem is you did not copy my code correctly, there is an error in your reshape routine.

Also if you like I can e-mail you a example drawing program I wrote, just drop me a e-mail.

See corrections below

Here is my reshape function :
void myGlutReshape( int x, int y )
{
int tx, ty, tw, th; //
Winx= tw; <----error you set Winx to zero every call here...
Winy= th;
// Correct code
Winx = x;
Winy = y;

// tx, ty, tw, th; all have zero until this is called
GLUI_Master.get_viewport_area( &tx, &ty, &tw, &th );
glViewport( tx, ty, tw, th );

// xy_aspect = (float)tw / (float)th;

glutPostRedisplay();
}


I beleived my world is between ( -80,-80, 80,80) and my viewport is 600 × 600 .


Thank you in advance

[This message has been edited by nexusone (edited 12-04-2003).]

[glcrazy]

Hi nexusone

the problem still there even I changed what you tell me to change ..I beleive it give me a zero somewhere in the second part of the equation here .. x = -80 + 160 * ( x/ Winx) .. because the value of x remains -80 always the same happened to y..

I checked the value of intial x .. it's not zero , Winx also not zero .. but the value of x after the equation is always -80 !!!

I don't know where I'm wrong exactly ..

Thanks for any help ..