// IntersectAxis checks whether there's interaction between the ray and the box.
func (b *BoundingBox) IntersectAxis(ray *ray.Ray, axis int) bool {
directions := [3]float64{ray.Direction.X, ray.Direction.Y, ray.Direction.Z}
start := [3]float64{ray.Start.X, ray.Start.Y, ray.Start.Z}
// if the ray isn't pointing at the box there wouldn't be an intersection
if (directions[axis] > 0 && start[axis] > b.MaxVolume[axis]) ||
(directions[axis] < 0 && start[axis] < b.MinVolume[axis]) {
return false
}
// or if the ray isn't moving in this direction at all
if math.Abs(directions[axis]) < maths.Epsilon {
return false
}
// we take the other two axes
otherAxis1, otherAxis2 := otherAxes(axis)
multiplier := ray.Inverse[axis]
var intersectionX, intersectionY float64
distance := (b.MinVolume[axis] - start[axis]) * multiplier
if distance < 0 {
return false
}
intersectionX = start[otherAxis1] + directions[otherAxis1]*distance
if maths.Between(b.MinVolume[otherAxis1], b.MaxVolume[otherAxis1], intersectionX) {
intersectionY = start[otherAxis2] + directions[otherAxis2]*distance
if maths.Between(b.MinVolume[otherAxis2], b.MaxVolume[otherAxis2], intersectionY) {
return true
}
}
distance = (b.MaxVolume[axis] - start[axis]) * multiplier
if distance < 0 {
return false
}
intersectionX = start[otherAxis1] + directions[otherAxis1]*distance
if maths.Between(b.MinVolume[otherAxis1], b.MaxVolume[otherAxis1], intersectionX) {
intersectionY = start[otherAxis2] + directions[otherAxis2]*distance
if maths.Between(b.MinVolume[otherAxis2], b.MaxVolume[otherAxis2], intersectionY) {
return true
}
}
return false
}
// Inside checks if a point is inside the box
func (b *BoundingBox) Inside(point *maths.Vec3) bool {
return (maths.Between(b.MinVolume[0], b.MaxVolume[0], point.X) &&
maths.Between(b.MinVolume[1], b.MaxVolume[1], point.Y) &&
maths.Between(b.MinVolume[2], b.MaxVolume[2], point.Z))
}
