Zooming into the mouse position with a translation?

To zo开发者_如何转开发om into the mouse position I was using:

glTranslatef(current.ScalePoint.x,current.ScalePoint.y,0);
    glScalef(current.ScaleFactor,current.ScaleFactor,current.ScaleFactor);
    glTranslatef(-current.ScalePoint.x,-current.ScalePoint.y,0);

so basically I translate to the new origin (the mouse position) then scale by the current scale factor, then translate back.

This kind of works generally well, but it can be a bit buggy. My issue is really that now I'v introduced a camera offset so I tried something like this:

glTranslatef(controls.MainGlFrame.GetCameraX(),
    controls.MainGlFrame.GetCameraY(),0);
glTranslatef(current.ScalePoint.x,current.ScalePoint.y,0);


glScalef(current.ScaleFactor,current.ScaleFactor,current.ScaleFactor);
glTranslatef(-current.ScalePoint.x,-current.ScalePoint.y,0);

But this did not work as I intended. How could I properly do this knowing that:

The matrix's origin is the top left corner (0,0)

1 unit == 1 pixel

My scale factor

My camera's position relative to how far it is from (0,0) (the origin) and

the mouse position (screen to client).

Thanks

It is more safe (and also for code reuse) to un-project the mouse coordinate point (from window coordinates to model coordinates) first even though you know how projection is done.

You can use the following function:

void unProject(int ix, int iy, int &ox, int &oy)
{
 // First, ensure that your OpenGL context is the selected one
 GLint viewport[4];
 GLdouble projection[16];
 GLdouble modelview[16];

 glGetIntegerv(GL_VIEWPORT, viewport);
 glGetDoublev(GL_PROJECTION_MATRIX, projection);
 glGetDoublev(GL_MODELVIEW_MATRIX, modelview);

 int xx = ix;
 int yy = viewport[3] - iy;
 GLdouble x, y, z;
 gluUnProject(xx, yy, 0 /*check*/, modelview, projection, viewport, &x, &y, &z);

 ox = (int) x;
 oy = (int) y;
}

The output then is the correct point on the model coordinates for your zooming