Title: An eassy procedure to draw a Vector Field
Question: This coded is useful is you have to draw a velocity field in a two dimensional mesh
Answer:
This procedure draw vectors on a Chart component.
procedure TDatosInput.Vector(VArrayX,VArrayY: TArray2D; VArrayU,VArrayV: TArray3D; nx,ny,nt: DWord; Malla: TPointSeries; Chrt: TChart; ColorVector: TColor; Fact: DWord);
var
i,j,PosX: DWord;
xi,yi,xf,yf: Longint;
Xn,Yn: Extended;
Dx,Dy: Extended;
Ang: Extended;
begin
{Config Canvas}
Chrt.Canvas.Pen.Color:=ColorVector;
Chrt.Canvas.Brush.Color:=ColorVector;
{Paint Color at each cell}
for j:=0 to ny-1 do
for i:=0 to nx-1 do
begin
{Calc Angle}
PosX:=i;
if (i = nx-1) then PosX:=nx-2;
Dx:=VArrayX[PosX+1,j]-VArrayX[PosX,j];
Dy:=VArrayY[PosX+1,j]-VArrayY[PosX,j];
{Check Dx}
Ang:=0;
if (Dx = 0) or (Dy = 0) then
begin
if (Dy 0) and (Dx = 0) then Ang:=0.5*Pi;
if (Dy if (Dy = 0) and (Dx 0) then Ang:=0;
if (Dy = 0) and (Dx end
else
begin
Ang:=ArcTan(Dy/Dx);
{Check Position}
if ((Dy 0) or (Dy Ang:=Ang+Pi;
end;
{New Coordinates - Rotating the Vector}
xn:=VArrayU[i,j,nt]*Fact*Cos(Ang)-VArrayV[i,j,nt]*Fact*Sin(Ang);
yn:=VArrayU[i,j,nt]*Fact*Sin(Ang)+VArrayV[i,j,nt]*Fact*Cos(Ang);
{Drawing the Arrow}
xi:=Malla.CalcXPosValue(VArrayX[i,j]);
yi:=Malla.CalcYPosValue(VArrayY[i,j]);
xf:=Malla.CalcXPosValue(xn+VArrayX[i,j]);
yf:=Malla.CalcYPosValue(yn+VArrayY[i,j]);
Chrt.Canvas.Arrow(False,Point(xi,yi),Point(xf,yf),5,10,0);
end;
end;