public override void UpdateTimeOfImpact(Collidable requester, float dt)
{
var overlap = BroadPhaseOverlap;
var triangleMode = triangle.entity == null ? PositionUpdateMode.Discrete : triangle.entity.PositionUpdateMode;
var convexMode = convex.entity == null ? PositionUpdateMode.Discrete : convex.entity.PositionUpdateMode;
if (
(overlap.entryA.IsActive || overlap.entryB.IsActive) && //At least one has to be active.
(
(
convexMode == PositionUpdateMode.Continuous && //If both are continuous, only do the process for A.
triangleMode == PositionUpdateMode.Continuous &&
overlap.entryA == requester
) ||
(
convexMode == PositionUpdateMode.Continuous ^ //If only one is continuous, then we must do it.
triangleMode == PositionUpdateMode.Continuous
)
)
)
{
//Only perform the test if the minimum radii are small enough relative to the size of the velocity.
Vector3 velocity;
if (convexMode == PositionUpdateMode.Discrete)
{
//Triangle is static for the purposes of this continuous test.
velocity = triangle.entity.linearVelocity;
}
else if (triangleMode == PositionUpdateMode.Discrete)
{
//Convex is static for the purposes of this continuous test.
Vector3.Negate(ref convex.entity.linearVelocity, out velocity);
}
else
{
//Both objects are moving.
Vector3.Subtract(ref triangle.entity.linearVelocity, ref convex.entity.linearVelocity, out velocity);
}
Vector3.Multiply(ref velocity, dt, out velocity);
float velocitySquared = velocity.LengthSquared();
var minimumRadiusA = convex.Shape.minimumRadius * MotionSettings.CoreShapeScaling;
timeOfImpact = 1;
if (minimumRadiusA * minimumRadiusA < velocitySquared)
{
//Spherecast A against B.
RayHit rayHit;
if (GJKToolbox.CCDSphereCast(new Ray(convex.worldTransform.Position, -velocity), minimumRadiusA, triangle.Shape, ref triangle.worldTransform, timeOfImpact, out rayHit))
{
if (triangle.Shape.sidedness != TriangleSidedness.DoubleSided)
{
//Only perform sweep if the object is in danger of hitting the object.
//Triangles can be one sided, so check the impact normal against the triangle normal.
Vector3 AB, AC;
Vector3.Subtract(ref triangle.Shape.vB, ref triangle.Shape.vA, out AB);
Vector3.Subtract(ref triangle.Shape.vC, ref triangle.Shape.vA, out AC);
Vector3 normal;
Vector3.Cross(ref AB, ref AC, out normal);
float dot;
Vector3.Dot(ref rayHit.Normal, ref normal, out dot);
if (triangle.Shape.sidedness == TriangleSidedness.Counterclockwise && dot < 0 ||
triangle.Shape.sidedness == TriangleSidedness.Clockwise && dot > 0)
{
timeOfImpact = rayHit.T;
}
}
else
{
timeOfImpact = rayHit.T;
}
}
}
//TECHNICALLY, the triangle should be casted too. But, given the way triangles are usually used and their tiny minimum radius, ignoring it is usually just fine.
//var minimumRadiusB = triangle.minimumRadius * MotionSettings.CoreShapeScaling;
//if (minimumRadiusB * minimumRadiusB < velocitySquared)
//{
// //Spherecast B against A.
// RayHit rayHit;
// if (GJKToolbox.SphereCast(new Ray(triangle.entity.position, velocity), minimumRadiusB, convex.Shape, ref convex.worldTransform, 1, out rayHit) &&
// rayHit.T < timeOfImpact)
// {
// if (triangle.Shape.sidedness != TriangleSidedness.DoubleSided)
// {
// float dot;
// Vector3.Dot(ref rayHit.Normal, ref normal, out dot);
// if (dot > 0)
// {
// timeOfImpact = rayHit.T;
// }
// }
// else
// {
// timeOfImpact = rayHit.T;
// }
// }
//}
//If it's intersecting, throw our hands into the air and give up.
//This is generally a perfectly acceptable thing to do, since it's either sitting
//inside another object (no ccd makes sense) or we're still in an intersecting case
//from a previous frame where CCD took place and a contact should have been created
//to deal with interpenetrating velocity. Sometimes that contact isn't sufficient,
//but it's good enough.
if (timeOfImpact == 0)
timeOfImpact = 1;
}
}
