Continuing on working on my mouse moves in DrawSketchHandlerLineSet

Ok… So I thinking I’m approaching a point where the rubber hits the road…. Or  not… So… What I’m attempting to do is to add an arc to the polyline mode.

I came up with a sketch for solving the polyline arc

So basically A would be the first mouse click and B would be the second mouse click.

So what I need to do is to solve for C which would be the center of the arc.

Goal:
The goal in this sub-project is to determine  the vector position of the center of the Arc “C”.  Once  worked out, I’m on easy street (in this sub-project anyway) for  drawing the Arc in the mouse movement  since the code has  already been worked out

Figuring out the scalar value of VC what I need to do is to figure out the vector position of C

“A” would be the end point of the previous element and the starting point of the Arc.  It would make sense that if we’re drawing a polyline that the Arc should be tangent to the previous element.

That begs the questions… Is there a previous element. Looking at the code, I believe that question could be answered by getHighestCurveIndex().  The question, is that does this return if there is no prior curve?

This function is defined in:
class SketcherExport SketchObject : public Part::Part2DObject
as:
int getHighestCurveIndex(void) const { return Geometry.getSize() – 1; }

Stepping into this:

int DrawSketchHandler::getHighestCurveIndex(void)
{
return sketchgui->getSketchObject()->getHighestCurveIndex();
}
—-
Sketcher::SketchObject *ViewProviderSketch::getSketchObject(void) const
{
return dynamic_cast<Sketcher::SketchObject *>(pcObject);
}

—-

in SketchObject

—-

int getHighestCurveIndex(void) const { return Geometry.getSize() – 1; }

—

One thing that I still need to do is to execute a vector cross product. I was have discussion of how to do this on the #freecad IRC and one had showed how to do this in python:https://gist.github.com/2297556

// This file is generated by src/Tools/generateTemaplates/templateClassPyExport.py out of the .XML file
// Every change you make here get lost at the next full rebuild!
// This File is normaly build as an include in VectorPyImp.cpp! Its not intended to be in a project!

PyObject*  VectorPy::cross(PyObject *args)
{
PyObject *obj;
if (!PyArg_ParseTuple(args, “O!”, &(VectorPy::Type), &obj))
return 0;VectorPy* vec = static_cast<VectorPy*>(obj);VectorPy::PointerType this_ptr = reinterpret_cast<VectorPy::PointerType>(_pcTwinPointer);
VectorPy::PointerType vect_ptr = reinterpret_cast<VectorPy::PointerType>(vec->_pcTwinPointer);Base::Vector3d v = (*this_ptr) % (*vect_ptr);
return new VectorPy(v);
}

PyObject*  VectorPy::sub(PyObject *args)
{
PyObject *obj;
if (!PyArg_ParseTuple(args, “O!”, &(VectorPy::Type), &obj))
return 0;VectorPy* vec = static_cast<VectorPy*>(obj);VectorPy::PointerType this_ptr = reinterpret_cast<VectorPy::PointerType>(_pcTwinPointer);
VectorPy::PointerType vect_ptr = reinterpret_cast<VectorPy::PointerType>(vec->_pcTwinPointer);Base::Vector3d v = (*this_ptr) – (*vect_ptr);
return new VectorPy(v);
}

Ok.. now we have this.

It’s not up in this picture but I need to fix if the center of the arc is above the line or below the line.

So.. I think issue 1) is easy…

referring to http://www.cplusplus.com/reference/clibrary/cmath/atan/

and

http://www.cplusplus.com/reference/clibrary/cmath/atan2/
Atan2 returns Principal arc tangent of y/x, in the interval [-pi,+pi] radians.
What I need to wind up with is 0 to 2PI if I’m going to the left CCW and 0 to -2PI if I’m going CCW.
So.. I need to factor direction when I’m calculating the angle… (More on this later)
I had this vector reference bookmarked at work.. It’s a nice site… This really belongs in my useful links, but good for know

http://chortle.ccsu.edu/VectorLessons/vch09/vch09_6.html

http://free-cad.sourceforge.net/SrcDocu/d6/d23/Tools2D_8cpp_source.html#l00036

4-19 update…Getting tanalizing closer… Stupid logic errors that I almost have worked out for the CCW polyline arc.  I still done have the mousedown event written to draw the arc, so I revert to line (key up on the “A” to test the next case.  Here’s where it’s bombing.

4-21 update. Yeah… Arcs to draw out properly CCW condition. I’m going to get the  the code to respond to a hard set clockwise before start working on the CCW/CW selector.

This is the little section of code(Which works at the moment) that caused me such pain, no big deal..

(Just in case I need to get back to this point

// if ((kVec.z ==-1) ){//ccw
if (startAngle<=0 && finishAngle>=0  )
arcAngle = finishAngle – startAngle ;
else if (startAngle>=0  && finishAngle<=0 )
arcAngle = abs(finishAngle+ 2 * M_PI – startAngle);
else if(( startAngle<0 && finishAngle<0 )|| (startAngle>0 && finishAngle>0 )){//somewhere in the 3 or 4 quandrant
if (finishAngle>startAngle){
arcAngle =finishAngle-startAngle;

}
else{
arcAngle =finishAngle-startAngle+ 2* M_PI;
}

}
else
arcAngle = abs(finishAngle – startAngle);
//  }
// else
//  {

//  }
—–
Ok… I think I got the arcs to draw out properly for both ccw and cw conditions. Here’s the magic:

            if ((kVec.z ==-1) ){//ccw
if (startAngle<=0 && finishAngle>=0  )
arcAngle = finishAngle – startAngle ;
else if (startAngle>=0  && finishAngle<=0 )
arcAngle = abs(finishAngle+ 2 * M_PI – startAngle);
else if(( startAngle<0 && finishAngle<0 )|| (startAngle>0 && finishAngle>0 )){//BOTH START AND FINISH EITHER UPPER OR LOWER QUANDRANTS
if (finishAngle>startAngle){
arcAngle =finishAngle-startAngle;

}
else{
arcAngle =finishAngle-startAngle+ 2* M_PI;
}

}
else
arcAngle = abs(finishAngle – startAngle);//Don’t think this point is ever reached
}
else{//cw rotation
if (startAngle<=0 && finishAngle>=0  )
arcAngle = abs(finishAngle – startAngle-2 *M_PI) ;
else if (startAngle>=0  && finishAngle<=0 )
arcAngle = abs( -finishAngle + startAngle);
else if(( startAngle<0 && finishAngle<0 )|| (startAngle>0 && finishAngle>0 )){//BOTH START AND FINISH EITHER UPPER OR LOWER QUANDRANTS
if (finishAngle>startAngle){

arcAngle =abs(finishAngle-startAngle- 2* M_PI);

}
else{
arcAngle =abs(finishAngle-startAngle);

}

}
else
arcAngle = abs(finishAngle – startAngle);
}

rx = EditCurve[0].fX – CenterPoint.fX;
ry = EditCurve[0].fY – CenterPoint.fY;
for (int i=1; i <= 29; i++) {
float angle = i*arcAngle/29.0;
float dx,dy;
if (kVec.z ==-1){
dx = rx * cos(angle) – ry * sin(angle);
dy = rx * sin(angle) + ry * cos(angle);
}
else{
dx = rx * cos(-angle) – ry * sin(-angle);
dy = rx * sin(-angle) + ry * cos(-angle);
}

EditCurve[i] = Base::Vector2D(CenterPoint.fX + dx, CenterPoint.fY + dy);
}
EditCurve[30]=CenterPoint;
EditCurve[31]= EditCurve[0];

sketchgui->drawEdit(EditCurve);
if (seekAutoConstraint(sugConstr3, onSketchPos, Base::Vector2D(0.f,0.f))) {
renderSuggestConstraintsCursor(sugConstr3);
return;
}
break;
}
applyCursor();

}

So… Unless I missed something as far as the arc logic in mouse moves… It’s done…. Now on to setting cw and ccw