//Helper method for mobile collidables.
internal void ExpandBoundingBox(ref BoundingBox boundingBox, float dt)
{
//Expand bounding box with velocity.
if (dt > 0)
{
bool useExtraExpansion = MotionSettings.UseExtraExpansionForContinuousBoundingBoxes && entity.PositionUpdateMode == PositionUpdateMode.Continuous;
float velocityScaling = useExtraExpansion ? 2 : 1;
if (entity.linearVelocity.X > 0)
boundingBox.Max.X += entity.linearVelocity.X * dt * velocityScaling;
else
boundingBox.Min.X += entity.linearVelocity.X * dt * velocityScaling;
if (entity.linearVelocity.Y > 0)
boundingBox.Max.Y += entity.linearVelocity.Y * dt * velocityScaling;
else
boundingBox.Min.Y += entity.linearVelocity.Y * dt * velocityScaling;
if (entity.linearVelocity.Z > 0)
boundingBox.Max.Z += entity.linearVelocity.Z * dt * velocityScaling;
else
boundingBox.Min.Z += entity.linearVelocity.Z * dt * velocityScaling;
if (useExtraExpansion)
{
float expansion = 0;
//It's possible that an object could have a small bounding box since its own
//velocity is low, but then a collision with a high velocity object sends
//it way out of its bounding box. By taking into account high velocity objects
//in danger of hitting us and expanding our own bounding box by their speed,
//we stand a much better chance of not missing secondary collisions.
foreach (var e in OverlappedEntities)
{
float velocity = e.linearVelocity.LengthSquared();
if (velocity > expansion)
expansion = velocity;
}
expansion = (float)Math.Sqrt(expansion) * dt;
boundingBox.Min.X -= expansion;
boundingBox.Min.Y -= expansion;
boundingBox.Min.Z -= expansion;
boundingBox.Max.X += expansion;
boundingBox.Max.Y += expansion;
boundingBox.Max.Z += expansion;
}
//Could use this to incorporate angular motion. Since the bounding box is an approximation to begin with,
//this isn't too important. If an updating system is used where the bounding box MUST fully contain the frame's motion
//then the commented area should be used.
//Math.Min(entity.angularVelocity.Length() * dt, Shape.maximumRadius) * velocityScaling;
//TODO: consider using minimum radius
}
boundingBox.Validate();
}