Game Development Reference
In-Depth Information
// p0/q0 are the spheres last frame
// p1/q1 are the spheres this frame
function
SweptSphere(
BoundingSphere
p0,
Boundin-
gSphere
q0,
BoundingSphere
p1,
Boundin-
gSphere
q1)
// First calculate v vectors for parametric
equations
Vector3
vp
=
p1
.
center
-
p0
.
center
Vector3
vq
=
q1
.
center
-
q0
.
center
// Calculate A and B
// A = P0 - Q0
Vector3
A
=
p0
.
center
-
q0
.
center
// B = vp - vq
Vector3
B
=
vp
-
vq
// Calculate a, b, and c
// a = B dot B
float
a
= DotProduct(
B
,
B
)
// b = 2(A dot B)
float
b
= 2 * (DotProduct(
A
,
B
)
// c = (A dot A) - (rp + rq) * (rp + rq)
float
c = DotProduct(
A
,
A
) - ((
q0
.
radius
+
p0
.
radius
) *
(
q0
.
radius
+
p0
.
radius
))
// Now calculate the discriminant (b^2 - 4ac)
float
disc
=
b
*
b
- 4 *
a
*
c
if
disc
>= 0
// If we needed the value of t, we could cal-
culate it with:
// t = (-b - sqrt(disc)) / (2a)
// However, this simplified function just re-
turns true to say
// than an intersection occurred.
return true
