// From Eric Jordan's convex decomposition library
/// <summary>
/// Checks if polygon is valid for use in Box2d engine.
/// Last ditch effort to ensure no invalid polygons are
/// added to world geometry.
///
/// Performs a full check, for simplicity, convexity,
/// orientation, minimum angle, and volume. This won't
/// be very efficient, and a lot of it is redundant when
/// other tools in this section are used.
/// </summary>
/// <returns></returns>
public bool CheckPolygon()
{
int error = -1;
if (Count < 3 || Count > Settings.MaxPolygonVertices)
{
error = 0;
}
if (!IsConvex())
{
error = 1;
}
if (!IsSimple())
{
error = 2;
}
if (GetArea() < Settings.Epsilon)
{
error = 3;
}
//Compute normals
Vector2[] normals = new Vector2[Count];
Vertices vertices = new Vertices(Count);
for (int i = 0; i < Count; ++i)
{
vertices.Add(new Vector2(this[i].X, this[i].Y));
int i1 = i;
int i2 = i + 1 < Count ? i + 1 : 0;
Vector2 edge = new Vector2(this[i2].X - this[i1].X, this[i2].Y - this[i1].Y);
normals[i] = MathUtils.Cross(edge, 1.0f);
normals[i].Normalize();
}
//Required side checks
for (int i = 0; i < Count; ++i)
{
int iminus = (i == 0) ? Count - 1 : i - 1;
//Parallel sides check
float cross = MathUtils.Cross(normals[iminus], normals[i]);
cross = MathUtils.Clamp(cross, -1.0f, 1.0f);
float angle = ( float )Math.Asin(cross);
if (angle <= Settings.AngularSlop)
{
error = 4;
break;
}
//Too skinny check
for (int j = 0; j < Count; ++j)
{
if (j == i || j == (i + 1) % Count)
{
continue;
}
float s = Vector2.Dot(normals[i], vertices[j] - vertices[i]);
if (s >= -Settings.LinearSlop)
{
error = 5;
}
}
Vector2 centroid = vertices.GetCentroid();
Vector2 n1 = normals[iminus];
Vector2 n2 = normals[i];
Vector2 v = vertices[i] - centroid;
Vector2 d = new Vector2();
d.X = Vector2.Dot(n1, v); // - toiSlop;
d.Y = Vector2.Dot(n2, v); // - toiSlop;
// Shifting the edge inward by toiSlop should
// not cause the plane to pass the centroid.
if ((d.X < 0.0f) || (d.Y < 0.0f))
{
error = 6;
}
}
if (error != -1)
{
Debug.WriteLine("Found invalid polygon, ");
switch (error)
{
case 0:
Debug.WriteLine(string.Format("must have between 3 and {0} vertices.\n",
Settings.MaxPolygonVertices));
break;
case 1:
Debug.WriteLine("must be convex.\n");
break;
case 2:
Debug.WriteLine("must be simple (cannot intersect itself).\n");
break;
case 3:
Debug.WriteLine("area is too small.\n");
break;
case 4:
Debug.WriteLine("sides are too close to parallel.\n");
break;
case 5:
Debug.WriteLine("polygon is too thin.\n");
break;
case 6:
Debug.WriteLine("core shape generation would move edge past centroid (too thin).\n");
break;
default:
Debug.WriteLine("don't know why.\n");
break;
}
}
return(error != -1);
}
// From Eric Jordan's convex decomposition library
/// <summary>
/// Checks if polygon is valid for use in Box2d engine.
/// Last ditch effort to ensure no invalid polygons are
/// added to world geometry.
///
/// Performs a full check, for simplicity, convexity,
/// orientation, minimum angle, and volume. This won't
/// be very efficient, and a lot of it is redundant when
/// other tools in this section are used.
/// </summary>
/// <returns></returns>
public bool CheckPolygon(out int error, out string errorMessage)
{
error = -1;
errorMessage = null;
if (Count < 3 || Count > Settings.MaxPolygonVertices)
{
error = 0;
}
if (!IsConvex())
{
error = 1;
}
if (!IsSimple())
{
error = 2;
}
if (GetArea() < Settings.Epsilon)
{
error = 3;
}
//Compute normals
Vector2[] normals = new Vector2[Count];
Vertices vertices = new Vertices(Count);
for (int i = 0; i < Count; ++i)
{
vertices.Add(new Vector2(this[i].x, this[i].y));
int i1 = i;
int i2 = i + 1 < Count ? i + 1 : 0;
Vector2 edge = new Vector2(this[i2].x - this[i1].x, this[i2].y - this[i1].y);
normals[i] = MathUtils.Cross(edge, 1.0f);
normals[i].Normalize();
}
//Required side checks
for (int i = 0; i < Count; ++i)
{
int iminus = (i == 0) ? Count - 1 : i - 1;
//Parallel sides check
float cross = MathUtils.Cross(normals[iminus], normals[i]);
cross = MathUtils.Clamp(cross, -1.0f, 1.0f);
float angle = Mathf.Asin(cross);
if (angle <= Settings.AngularSlop)
{
error = 4;
break;
}
//Too skinny check
for (int j = 0; j < Count; ++j)
{
if (j == i || j == (i + 1) % Count)
{
continue;
}
float s = Vector2.Dot(normals[i], vertices[j] - vertices[i]);
if (s >= -Settings.LinearSlop)
{
error = 5;
}
}
Vector2 centroid = vertices.GetCentroid();
Vector2 n1 = normals[iminus];
Vector2 n2 = normals[i];
Vector2 v = vertices[i] - centroid;
Vector2 d = new Vector2();
d.x = Vector2.Dot(n1, v); // - toiSlop;
d.y = Vector2.Dot(n2, v); // - toiSlop;
// Shifting the edge inward by toiSlop should
// not cause the plane to pass the centroid.
if ((d.x < 0.0f) || (d.y < 0.0f))
{
error = 6;
}
}
if (error != -1)
{
switch (error)
{
case 0:
errorMessage = string.Format("Polygon error: must have between 3 and {0} vertices.",
Settings.MaxPolygonVertices);
break;
case 1:
errorMessage = "Polygon error: must be convex.";
break;
case 2:
errorMessage = "Polygon error: must be simple (cannot intersect itself).";
break;
case 3:
errorMessage = "Polygon error: area is too small.";
break;
case 4:
errorMessage = "Polygon error: sides are too close to parallel.";
break;
case 5:
errorMessage = "Polygon error: polygon is too thin.";
break;
case 6:
errorMessage = "Polygon error: core shape generation would move edge past centroid (too thin).";
break;
default:
errorMessage = "Polygon error: error " + error.ToString();
break;
}
}
return(error != -1);
}