Category: **Math**

Title: **Determine if a 2D point exists within a 2D triangle**

Date added: **15.03.2006**

Hits: **6837**
**function** PntInTriangle(Px, Py, x1, y1, x2, y2, x3, y3: Double): Boolean;

**var**
Or1, Or2, Or3: Double;

**begin**
Or1 := Orientation(x1, y1, x2, y2, Px, Py);

Or2 := Orientation(x2, y2, x3, y3, Px, Py);

Or3 := Orientation(x3, y3, x1, y1, Px, Py);

Result := (Or1 = Or2) and (Or2 = Or3);

**end;**
**function** Orientation(x1, y1, x2, y2, Px, Py: Double): Integer;

**var**
Orin: Double;

**begin**
Orin := (x2 - x1) * (py - y1) - (px - x1) * (y2 - y1);

**if** Orin > 0.0

**then** Result := +1

else

**if** Orin < 0.0

**then** Result := -1

else

Result := 0;

**end;**