/// <summary>
/// Workhorse for circle-circle collisions, compares origin distance
/// to the sum of the two circles' radii, returns a Manifold.
/// </summary>
///
private static Manifold TestCircles(
VoltWorld world,
VoltCircle shapeA,
VoltShape shapeB,
TSVector2 overrideBCenter, // For testing vertices in circles
FP overrideBRadius)
{
TSVector2 r = overrideBCenter - shapeA.worldSpaceOrigin;
FP min = shapeA.radius + overrideBRadius;
FP distSq = r.sqrMagnitude;
if (distSq >= min * min)
{
return(null);
}
FP dist = TSMath.Sqrt(distSq);
FP distInv = 1.0f / dist;
TSVector2 pos =
shapeA.worldSpaceOrigin +
(0.5f + distInv * (shapeA.radius - min / 2.0f)) * r;
// Build the collision Manifold
Manifold manifold =
world.AllocateManifold().Assign(world, shapeA, shapeB);
manifold.AddContact(pos, distInv * r, dist - min);
return(manifold);
}
internal Manifold Assign(
VoltWorld world,
VoltShape shapeA,
VoltShape shapeB)
{
this.world = world;
this.ShapeA = shapeA;
this.ShapeB = shapeB;
this.Restitution = TSMath.Sqrt(shapeA.Restitution * shapeB.Restitution);
this.Friction = TSMath.Sqrt(shapeA.Friction * shapeB.Friction);
this.used = 0;
return(this);
}
/// <summary>
/// Checks a ray against a circle with a given origin and square radius.
/// </summary>
internal static bool CircleRayCast(
VoltShape shape,
TSVector2 shapeOrigin,
FP sqrRadius,
ref VoltRayCast ray,
ref VoltRayResult result)
{
TSVector2 toOrigin = shapeOrigin - ray.origin;
if (toOrigin.sqrMagnitude < sqrRadius)
{
result.SetContained(shape);
return(true);
}
FP slope = TSVector2.Dot(toOrigin, ray.direction);
if (slope < 0)
{
return(false);
}
FP sqrSlope = slope * slope;
FP d = sqrRadius + sqrSlope - TSVector2.Dot(toOrigin, toOrigin);
if (d < 0)
{
return(false);
}
FP dist = slope - TSMath.Sqrt(d);
if (dist < 0 || dist > ray.distance)
{
return(false);
}
// N.B.: For historical raycasts this normal will be wrong!
// Must be either transformed back to world or invalidated later.
TSVector2 normal = (dist * ray.direction - toOrigin).normalized;
result.Set(shape, dist, normal);
return(true);
}