/// <summary>
/// This is a high-level function to cuts fixtures inside the given world, using the start and end points.
/// Note: We don't support cutting when the start or end is inside a shape.
/// </summary>
/// <param name="world">The world.</param>
/// <param name="start">The startpoint.</param>
/// <param name="end">The endpoint.</param>
/// <returns>True if the cut was performed.</returns>
public static bool Cut(World world, FPVector2 start, FPVector2 end)
{
List <Fixture> fixtures = new List <Fixture>();
List <FPVector2> entryPoints = new List <FPVector2>();
List <FPVector2> exitPoints = new List <FPVector2>();
//We don't support cutting when the start or end is inside a shape.
if (world.TestPoint(start) != null || world.TestPoint(end) != null)
{
return(false);
}
//Get the entry points
world.RayCast((f, p, n, fr) =>
{
fixtures.Add(f);
entryPoints.Add(p);
return(1);
}, start, end);
//Reverse the ray to get the exitpoints
world.RayCast((f, p, n, fr) =>
{
exitPoints.Add(p);
return(1);
}, end, start);
//We only have a single point. We need at least 2
if (entryPoints.Count + exitPoints.Count < 2)
{
return(false);
}
for (int i = 0; i < fixtures.Count; i++)
{
// can't cut circles or edges yet !
if (fixtures[i].Shape.ShapeType != ShapeType.Polygon)
{
continue;
}
if (fixtures[i].Body.BodyType != BodyType.Static)
{
//Split the shape up into two shapes
Vertices first;
Vertices second;
SplitShape(fixtures[i], entryPoints[i], exitPoints[i], out first, out second);
//Delete the original shape and create two new. Retain the properties of the body.
if (first.CheckPolygon() == PolygonError.NoError)
{
Body firstFixture = BodyFactory.CreatePolygon(world, first, fixtures[i].Shape.Density, fixtures[i].Body.Position);
firstFixture.Rotation = fixtures[i].Body.Rotation;
firstFixture.LinearVelocity = fixtures[i].Body.LinearVelocity;
firstFixture.AngularVelocity = fixtures[i].Body.AngularVelocity;
firstFixture.BodyType = BodyType.Dynamic;
}
if (second.CheckPolygon() == PolygonError.NoError)
{
Body secondFixture = BodyFactory.CreatePolygon(world, second, fixtures[i].Shape.Density, fixtures[i].Body.Position);
secondFixture.Rotation = fixtures[i].Body.Rotation;
secondFixture.LinearVelocity = fixtures[i].Body.LinearVelocity;
secondFixture.AngularVelocity = fixtures[i].Body.AngularVelocity;
secondFixture.BodyType = BodyType.Dynamic;
}
world.RemoveBody(fixtures[i].Body);
}
}
return(true);
}