Picking for Web-Based 3D Experiment - Interactive Web-Based Virtual Reality with Java 3D - page 385

if (returnposi>(slideposi[i]+slideposi[i+1])/2.0f)

{

returnposi = slideposi[i];

}

else

{

returnposi = slideposi[i+1];

}

}

}

return returnposi;

}

h.20 calculatInG mouse anGle relatIve to knob

//Returning the value of the current angle

private float CalAngle(Point3f part, Point3f component, Point3f CurrentPt)

{

float angle;

angle = (float)(Math.atan2(CurrentPt.x-component.x-part.x,

CurrentPt.y-component.y-part.y)/Math.PI);

angle = (-angle+1.0f)*PAI - PAI/2.0f;

if (angle<0.0f) angle = angle+2.0f*PAI; //The angle value is negative

return angle; //Returning the angle value of 0 to 2*PAI

}

h.21 calculatInG chanGe In mouse anGle

//Returning the angle difference between the current angle and last one

private float DeltaAngle(float currentangle, float lastangle)

{

float delta;

if (currentangle-lastangle>2.0f)

{

// currentangle is in the 4th phase and lastangle is in the 1st phase

delta = currentangle - lastangle - 2.0f*PAI;

}

else if (currentangle-lastangle<-2.0f)

{

// currentangle is in the 1st phase and lastangle is in the 4th phase

delta = currentangle -lastangle + 2.0f*PAI;

}

else

{

delta = currentangle -lastangle;

}

return delta;

}