[gameprogrammer] Math Problem
- From: "Edilson Vasconcelos de Melo Junior" <dirso@xxxxxxxxxxxxxxxxxx>
- To: <gameprogrammer@xxxxxxxxxxxxx>
- Date: Fri, 18 Jul 2008 16:21:02 -0300
Hi!
I'm almost there with my array design to indicate the path.
My solution was: reduce the problem to a 2d issue, then draw two small line
segments attached to the target point. It was not that hard, I just found
the dimension with less difference between pointA (source) and pointB
(target), ignore it and the rotate a normalized -(pointB - pointA) by PI/6
and -PI/6, so I was suppose to have the triangle faces, but I didn't, both
faces looks the same, and I think it's a sin/cos issue that I could solve.
Here is my code.
public static Vector2 rotateVector(Vector2 v, double angle)
{
double ca = Math.Cos(angle), sa = Math.Sin(angle);
return new Vector2((float)(v.X*ca + v.Y*sa),
(float)(v.X*(-sa) + v.Y*ca));
}
public void calcDwTriangle(int index, Vector3 p1, Vector3 p2)
{
#region dwTriangles
int icode;
if(Math.Abs(p1.X - p2.X) < Math.Abs(p1.Y - p2.Y))
{
if(Math.Abs(p1.X - p2.X) < Math.Abs(p1.Z - p1.Z))
icode = 0;
else icode = 2;
}
else
{
if(Math.Abs(p1.Y - p2.Y) < Math.Abs(p1.Z - p2.Z))
icode = 1;
else icode = 2;
}
Vector2 pontoA, pontoB;
switch(icode)
{
case 0: // take off X
pontoA = new Vector2(p1.Y, p1.Z);
pontoB = new Vector2(p2.Y, p2.Z);
break;
case 1: // take off Y
pontoA = new Vector2(p1.X, p1.Z);
pontoB = new Vector2(p2.X, p2.Z);
break;
default: // case 2 // take off Z
pontoA = new Vector2(p1.X, p1.Y);
pontoB = new Vector2(p2.X, p2.Y);
break;
}
Vector2 dir = pontoB - pontoA;
float len = dir.Length();
float arrowHeadWidth = 10.0f;
float arrowHeadLength =
(float)Math.Sqrt(Math.Pow(arrowHeadWidth,2.0f) + Math.Pow(arrowHeadWidth *
0.5f, 2.0f));
dir.Normalize();
Vector2 midPoint = pontoB - scalarMultiply(dir,
arrowHeadLength);
Vector2 newDir = -dir;
double a = Math.Atan2(dir.Y, dir.X);
Vector2 a1 = rotateVector(newDir, Math.PI/6),
a2 = rotateVector(newDir, -Math.PI/6);
a1.Normalize();
a2.Normalize();
a1 = scalarMultiply(a1, arrowHeadWidth * 0.5f);
a2 = scalarMultiply(a2, arrowHeadWidth * 0.5f);
a1 += midPoint;
a2 += midPoint;
dwTriangles[index][1].Position = p2;
switch(icode)
{
case 0: // tira o X
dwTriangles[index][0].Position = new
Vector3(p2.X, a1.X, a1.Y);
dwTriangles[index][2].Position = new
Vector3(p2.X, a2.X, a2.Y);
break;
case 1: // tira o Y
dwTriangles[index][0].Position = new
Vector3(a1.X, p2.Y, a1.Y);
dwTriangles[index][2].Position = new
Vector3(a2.X, p2.Y, a2.Y);
break;
default: // case 2 // tira o Z
dwTriangles[index][0].Position = new
Vector3(a1.X, a1.Y, p2.Z);
dwTriangles[index][2].Position = new
Vector3(a2.X, a2.Y, p2.Z);
break;
}
#endregion
}
Does anyone know a workaround for that?
Thanks,
Dirso
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