Problem in converting mouse coordinates

How you convert mouse coodinates? If you simply use V3d_View::Convert as FAQ pinpoints, it will give incorrect result. But in MFC Samples there is a function ConvertClickToPoint, it works well in my code.

fhchina

Hi,

as fhchina said in a previous post, use the function ConvertClickToPoint ( see at the bottom of this mail )

I wrote this function because of a problem I had converting 2d point in 3d.
The function V3d_View::Convert works fine.
The only problem is that you cannot control the "depth" of your click.
With this function, you have a better result.
In OpenCASCADE, when you are rotating your view, the Eye and Target points are updated according to ( more or less ) the last 3d point you picked ( during a selection ) or to the center of your objects.

So, I created a plane perpendicular to the view direction passing through the target point ( AtPoint ). After that, the converted 3d point ( the "wrong" point ) is projected on this plane, giving you a 2d point ( ConvertedPointOnPlane ). This 2d point is converted in 3d and returned.

With this function, the converted point is always ( quite ) near to the last selected point, so the result is better than the "original" convert function from V3d_View.

I hope it is clear enough.

Stephane
http://www.exotk.org

gp_Pnt ConvertClickToPoint(Standard_Real x, Standard_Real y, Handle(V3d_View) aView)
{

V3d_Coordinate XEye,YEye,ZEye,XAt,YAt,ZAt;
aView->Eye(XEye,YEye,ZEye);
aView->At(XAt,YAt,ZAt);
gp_Pnt EyePoint(XEye,YEye,ZEye);
gp_Pnt AtPoint(XAt,YAt,ZAt);

gp_Vec EyeVector(EyePoint,AtPoint);
gp_Dir EyeDir(EyeVector);

gp_Pln PlaneOfTheView = gp_Pln(AtPoint,EyeDir);
Standard_Real X,Y,Z;
aView->Convert(x,y,X,Y,Z);
gp_Pnt ConvertedPoint(X,Y,Z);
gp_Pnt2d ConvertedPointOnPlane = ProjLib::Project(PlaneOfTheView,ConvertedPoint);

gp_Pnt ResultPoint = ElSLib::Value(ConvertedPointOnPlane.X(),
ConvertedPointOnPlane.Y(),
PlaneOfTheView);
return ResultPoint;
}

Dear Stephane ;

The function you gave works on XY , XZ , YZ Views but in 3d Views , especially when I rotate the view with mouse it gives wrong points ;

I tried all the examples given over internet but none of them gave me the correct result in 3d view.

I really didint understand why? Any body had the same issue? and found a solution???

Hi, what do you mean exacltly?
I suppose, that when you switch to a 3D AXO projection, you get bad results.
Is it so?

If so, I have solved just such question , few months ago; so, I am able to draw interactively with mouse on XY, or XZ or YZ plane, staying in 3d AXO view.
Not sure 100% (because not tested) , on any oriented plane , ie say a plane with a normal of 1,1,1 . But I thnk of yes
Let me know if I have well understood your issue

Sure,give me just a day,to collect c++ code

Dear Selahattin ,Attached you find fragment of c++ code to draw a circle with mouse , dynamically , in a predefined "workplane". In my example , there are just 3 workplanes : XY,YZ and ZY. 
Maybe it runs for any Worplane ( I haven't check it).
In my application, at starting there 3 workplanes diplayed, and with the mooue , the user clicks on wnated WorPlane.I suggest you to move by step

Byway The key of all, is to "filter" and convert the mouse coordinate in WIndow coordinate , coming from events (onlButtonDown or OnMouseMove) , using the function  
gp_Pnt MyCadView::ConvertToPlane(Standard_Real x, Standard_Real y, Handle(V3d_View) aView,int nPlane)
This function accept :
The coordinate of mouse ( x,y,the handle to V3d_View) and the plane : in my code 0 for XY Plane,1 for YZ plane and 2 for XZ plane ( you can build any plane point origin + normal)
Then "draw" the circle with DrawCircle
In this way , you can draw with mouse any kind of entity 2d or also 3d ( box,cylinder....)
Let me know your opinion
Next step is draw with snaps,to draw with precision ( a bit hard..)