Confine Mouse Movement in a 3D plane?

Hi Mark,

I've got a small Qt4 bottle drawer demo based on an SDI model thats available on
http://myweb.tiscali.co.uk/dolbey/QtOpenCascade/

The discussion thread is on
http://www.opencascade.org/org/forum/thread_10338/

This is based on OCC 6.1, Qt 4.2.1 both compiled under VS2005 - there may be binary incompatibilities with using mixed compilations of OCC and Qt4 on different MS compilers.

I haven't yet added the point in plane code to the downloadable code yet. Since it was uploaded I've added some simple grid and view management functionality and I am currently trying to simplify the input/output code for the various file formats.

I think that most of the standard demos are obfuscating the *real* code by bad design. For instance, its my conjecture that views should be responsible for rendering images and sending appropriate events to the parent application. I don't know if my little library will come out any better but I'm trying to apply MVC principles in its design. In the case of the IO/routines, the demos are performing both import/export and GUI in the same class.

The point in plane code works of a kind, but I'm seeing some inaccuracy when I try to apply a precision < 1 world unit. However it should be up on the site during the week - look for the Doxygen release version to go up 0.3. (I didn't know if anyone else would be interested this week) - If I leave out the new i/o class (QtOCCInputOutput) it should be up in the next couple of days.

Pete

If you've got any comments about the code (i.e. how it might be better), put them in a post on this forum.

A long long time ago I went on a training course for CAS.CADE 1.5. I've kept most of the training materials, but haven't read them for years. Anyway for info, here's the old Matra documented way (updated a bit) for mapping screen points to 3d points on a plane - in my code I use the privileged plane of the view which can be used as a grid. (myPrecision is a constant set say to 0.01 for 2DPs).

Enjoy

Pete

/*!
ConvertToPlane convert 2d window position to 3d point on priviledged plane.
*/
Standard_Boolean QtOCCViewWidget::ConvertToPlane(const Standard_Integer Xs,
const Standard_Integer Ys,
Standard_Real& X,
Standard_Real& Y,
Standard_Real& Z,
Standard_Boolean usePrecision)
{
Standard_Real Xp = Xs, Yp = Ys;
Standard_Real Xv, Yv, Zv;
Standard_Real Vx, Vy, Vz;
gp_Pln aPlane(myView->Viewer()->PrivilegedPlane());
myView->Convert( Xp, Yp, Xv, Yv, Zv );
myView->Proj( Vx, Vy, Vz );
gp_Lin aLine(gp_Pnt(Xv, Yv, Zv), gp_Dir(Vx, Vy, Vz));
IntAna_IntConicQuad theIntersection (aLine, aPlane, Precision::Angular());
if (theIntersection.IsDone())
{
if (!theIntersection.IsParallel())
{
if (theIntersection.NbPoints() > 0)
{
gp_Pnt theSolution(theIntersection.Point(1));
X = theSolution.X();
Y = theSolution.Y();
Z = theSolution.Z();
if (usePrecision)
{
X = (X < 0. ? -1 : (X > 0. ? 1 : 0.)) * floor((abs(X)) / myPrecision) * myPrecision;
Y = (Y < 0. ? -1 : (Y > 0. ? 1 : 0.)) * floor((abs(Y)) / myPrecision) * myPrecision;
Z = (Z < 0. ? -1 : (Z > 0. ? 1 : 0.)) * floor((abs(Z)) / myPrecision) * myPrecision;
}
return Standard_True;
}
}
}
return Standard_False;
}